JP2889909B2 - Atmosphere meter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an atmosphere meter, and more particularly, to a gas meter by detecting the temperature of a resistor heated with low power in a measurement atmosphere based on a difference in the resistance value of the resistor. It relates to a self-temperature-compensated atmosphere gauge that detects the concentration. For example, it includes a flow sensor, gas chromatograph, vacuum gauge, dew point meter and hot wire anemometer, including a hygrometer, a mixed gas concentration meter, a partial pressure gauge and a distribution meter. It can be used for various instruments such as.

[0002]

2. Description of the Related Art There is known a method of thermally detecting a predetermined gas concentration contained in a mixed gas atmosphere based on a difference in thermal conductivity that changes according to a molecular weight of the predetermined gas. Among the atmosphere meters that use this principle, the hygrometer, in particular, has a wide range of applications, and is used for quality control for humidity control in processes of various industrial surfaces such as electronic parts such as semiconductors, optical precision equipment, textiles, and foods. Since it is widely used as a detection end for environmental management surfaces such as surfaces, hospitals, buildings, etc., the following description will be made on an example in which the atmosphere meter according to the present invention is applied to a hygrometer, but the present invention is limited to a hygrometer. However, the present invention relates to a general atmosphere meter having a different mixed gas concentration, specifically, to the various instruments described above. Thus, for example, as a principle of detecting the humidity of a hygrometer, there is a principle of detecting a change amount which is electrically and mechanically changed by moisture, but an electrical and mechanical one is based on various principles. There is something.
However, there are problems in reliability, life, and the like, and in many cases, responsiveness is generally poor.

[0003] Among them, a hygrometer utilizing the thermal conductivity of gas is known to have excellent responsiveness and high reliability. The amount of heat flowing in a unit time in the normal direction through the upper and lower surfaces of the predetermined cross section in the isotropic object is proportional to the temperature gradient and the cross sectional area in the normal direction, and this proportionality constant is the thermal conductivity. The thermal conductivity of a gas is a function of the specific heat at constant pressure, and the specific heat at constant pressure is a function of the molecular weight of the gas. Therefore, the thermal conductivity differs between the case of only air and the case where gas components and water having different molecular weights are contained in the air. A hygrometer utilizing the difference in the thermal conductivity of gas obtains humidity from the change in the resistance value of the resistor caused by the difference in the amount of heat radiated from the heated resistor into the atmosphere.

FIG. 24 is a partial cross-sectional view showing the structure of a conventional hygrometer. In the hygrometer 50, a temperature compensating element 51 and a detecting element 52 are placed close to each other on a heat equalizing plate 55 made of aluminum or the like having high thermal conductivity. It is configured to be arranged. Temperature compensation element 51
And the detecting element 52, a resistor 63 of the same size standard is arranged in a microbridge shape on a detecting chip 64, and this chip 64 is fixed on a high thermal conductive base 56 fixed on a heat equalizing plate 55. The resistor 63 is bonded via a lead pin 58 insulated by a hermetic seal. The difference between the temperature compensating element 51 and the detecting element 52 is that, in the temperature compensating element 51, the resistor 63 is sealed in the dry air at a constant pressure by the sealing cap 53, whereas in the detecting element 52, the sealing cap is The only difference is that the upper surface of 53 is covered with a breathable mesh 54.

[0005] In the hygrometer constructed as shown in the figure, both the temperature compensating element 51 and the resistor 63 of the detecting element 52 are heated with a constant power through the lead pin 58. Since the resistor 63 of the temperature compensating element 51 is covered with dry air of a constant pressure in the sealing cap 51, the resistor 63 changes only by the ambient temperature without being affected by the humidity of the outside air, and detects the outside temperature. .

On the other hand, the resistance of the resistor 63 of the detecting element 52 changes according to the temperature and humidity of the atmosphere containing moisture since the upper surface of the sealing cap 53 is covered with the mesh 54. Therefore, the resistance change due to humidity is calculated by subtracting the resistance value of the resistor 63 of the temperature compensation element 51 from the resistance value of the resistor 63 of the detection element 52. Actually, the change in the resistance value is detected as a voltage value.

However, the temperature compensating element 51 sealed by the sealing cap 53 has a small thermal conductivity between the resistor 63 and the sealing cap 53 when the ambient temperature changes rapidly. Because of the air buffer layer, it is not possible to quickly follow a change in the outside air temperature around the outer periphery of the sealing cap 53, and the response to the detection of the ambient temperature is delayed.

On the other hand, a detecting element 52 having a mesh 54
In this case, the response is fast because the ambient temperature is directly transmitted to the heated resistor 63. Therefore, when the atmosphere changes rapidly, an error occurs between the atmosphere temperature detected by the detection element 52 and the atmosphere temperature detected by the temperature compensation element 51.

FIGS. 25 (a), 25 (b), and 25 (c) are diagrams for explaining the occurrence of a detection error due to a response delay in detecting the ambient temperature of a conventional hygrometer. As shown in FIG. 25 (a), the ambient temperature T was 20 ° C. from time t ₀ (0 second) to t ₁ (0.01 second), but suddenly T ₂ (0.02 second) after T ₂ (0.02 second). = 4
When the temperature rises to 0 ° C. and is maintained at a constant temperature T = 40 ° C. after time t ₂ , at each time, FIG.
The temperature change component (indicated by voltage) of the detection element 52 of FIG.
FIG. 2B shows the temperature change component of the temperature compensation element 51 in FIG.
5 (c) is detected as indicated by oblique lines, and detected by the temperature compensation element 51 with a considerable time delay.

That is, the ambient temperature is set to the time t ₁ (0.01
When the temperature starts to rise uniformly from the temperature T = 20 ° C. at (second), the detection element 52 immediately detects ΔE ₁ b in response to the change in the ambient temperature T as shown in FIG. 25B. However, the temperature compensating element 51 detects the temperature in the state of T = 20 ° C. Time t _{1 to} t ₂ (0.01 to 0.02
Second) and after time t ₂ , the detection element 52
(B) quickly responds to changes in ambient temperature T,
While the temperature changes ΔE ₁ b and ΔE ₂ b are detected, the temperature compensation element 51 has no temperature change until time t ₂ (0.02 seconds) as shown in FIG. Time t ₂
Thereafter, the temperature change ΔE ₃ c is detected. That is, the temperature change ΔE ₃ c cannot be followed, and the response is delayed.
As a result, a humidity detection error corresponding to the detection delay of ΔE ₁ b, ΔE ₂ b and ΔE ₃ b−ΔE ₃ c occurs. Therefore,
In the case of an intermittent drive system using these elements by applying power for a short time, the temperature detected by the temperature compensation element 51 is:
Obviously, it will be different from the ambient temperature.

FIG. 26 shows another conventional hygrometer.
The conventional hygrometer shown in FIG. 24 is a general hygrometer using thermal conductivity, and there is a time delay due to the air layer of the temperature compensation element 52, whereas the hygrometer 60 shown in FIG. In order to reduce the thickness of the air layer of the temperature compensating element 52 shown in FIG. 22, which serves as a buffer layer, a detection chip 64 serving as a substrate is fixed to a base 62 in a sealing cap having a mesh 61. The compensation resistor 63 and the detection resistor 63 'are arranged in a microbridge shape, respectively, and further covered with a cap cover 66 for partitioning the temperature compensation resistor 63 and the detection resistor 63'.
7 is opened.

The temperature compensating resistor 63 is provided in the cap cover 66 for reducing the thickness of the air layer in order to reduce the time delay in the detection of the ambient temperature. This is the same as the temperature compensation element 51 of FIG.

FIG. 27 is a cross-sectional plan view showing the structure of another conventional hygrometer.
And the detection chamber 72 are disposed closer to each other by the heat equalizing sleeve 73, the detection chamber 72 is communicated with the outside air through the vent hole 74, and the temperature compensation chamber 71 has the temperature compensating element 63 (both ends in contact with the leads 75, 75). A detecting element 63 ′ (resistor R ₁₂ ) is connected to the leads 76, 76 at both ends of the resistor R ₁₁ ).

The ventilation hole 73 communicating with the detection chamber 72 has a smaller opening area than the case where a mesh is used, so that responsiveness is sacrificed. By doing so, attempts have been made to eliminate errors based on response time differences.

[0015] Figure 28 is a circuit configuration example of a humidity meter shown in FIG. 27, the detecting resistor R ₁₂ and the temperature compensating resistor R ₁₁ constitute a resistor R _13, R ₁₄ bridge circuit, terminal 78 , 7
DC power source connected to 9 (not shown) is connected via the R _15. Output a detection resistor R ₁₂ temperature compensating resistor R ₁₁
From both ends of the connected resistor Rm to the connection point between the connection points and the resistor R ₁₃ and R ₁₄ and is output via the terminal 80 and 81 as a voltage proportional to the humidity.

However, the hygrometer shown in FIG. 27 is small but is affected by the convection of the atmosphere. That is, since the degree of convection and the accuracy of the hole diameter and the hole position of the vent hole 74 are affected, it is difficult to balance the response time of the intended ambient temperature. Is not fundamentally improved.

[0017]

The problem common to the conventional examples having the temperature compensation element and the detection element described above is that unless dry air is sealed at a constant pressure, the thermal conductivity of the sealed gas changes, and the temperature increases. That is, the temperature detection characteristic of the compensating element itself changes, and the compensating element does not play a role of compensation.

Furthermore, since the constant pressure of the air sealed in the temperature compensating element is used as a compensation reference to detect the ambient humidity, if the ambient humidity pressure (external pressure) changes, the thermal conductivity also changes. Therefore, the effect of the reference is reduced. Therefore, it is necessary to precisely control the humidity of the dry air and the sealing conditions for sealing the dry air at a constant pressure, and these variations appear as characteristic variations during production, and at the same time, it is difficult to balance the combination of the detecting element and the temperature compensating element. As a result, the yield rate decreases.

Furthermore, since the pressure of the dry air filled in the temperature compensating element is constant, the pressure of the gas to be detected, that is, the thermal conductivity changes when used in ambient weather conditions or high altitude areas. Temperature compensation is possible if the internal pressure changes in the same way as the external pressure according to the operating conditions,
In particular, the conventional sealing cap shown in FIGS. 22 and 24 does not have a flexible material and structure that deforms due to fluctuations in atmospheric pressure and changes in internal pressure, and thus cannot provide accurate detection values.

When the atmosphere to be detected is partially uneven, the distance between the detecting element and the temperature compensating element is relatively large in the conventional example shown in FIGS. The resulting signal becomes a comparison value in the state of each location, and indicates a value at a detection position of scatter that is not a value at a detection position of one point (the same position), and is meaningless. Therefore, the distance between the detecting element and the temperature compensating element is preferably as short as possible, and may be combined on one substrate as in the conventional example shown in FIG. Nevertheless, since the detecting element and the temperature compensating element are still separated from each other, they are not suitable for more accurate measurement.

[0021]

In order to solve the above-mentioned problems, the present invention provides: (1) an atmosphere for detecting a predetermined gas in an atmosphere based on a change in the resistance of a resistor heated in the atmosphere; A low-temperature drive circuit for heating the resistor at a low temperature where the resistance change is affected only by the ambient temperature; and a high-temperature drive circuit for heating the resistor at a high temperature where the resistance change is sensitive to the temperature of the atmosphere and a predetermined gas. A circuit for comparing a voltage at a high temperature generated between both ends of the resistor with a voltage at a low temperature to a voltage at a low temperature, and detecting a concentration of a predetermined gas contained in the atmosphere according to an output voltage of the comparison and detection circuit; (2) a measurement ON / OFF signal generation circuit for determining a low-high temperature heating period and a heating suspension period, and a reference power generation circuit for heating a resistor in synchronization with the low-high temperature heating period. A time measurement circuit that determines a read timing for reading the resistance of the resistor as a voltage during low-temperature heating and high-temperature heating in synchronization with the low-high temperature heating period; and a voltage generated in the resistor in synchronization with the resistance value reading timing. A voltage measuring circuit for reading, a coefficient setting circuit for setting and multiplying a coefficient for correcting a voltage generated in the resistor during low-temperature heating to be a voltage corresponding to the ambient temperature and outputting a correction voltage, and a memory for storing the correction voltage Circuit, and a subtraction circuit for subtracting the stored correction voltage from the voltage generated in the resistor during the high-temperature heating, and obtaining a predetermined gas concentration in the atmosphere in proportion to the output of the subtraction circuit. (3) the resistor is a thin wire having a heat-generating action of generating heat by applying electric power, and both ends of the thin wire are insulated into a measurement gas via conductive pins; And (4) a low-high temperature heating period in which the resistor is heated at low and high temperatures, and after the heating period, the resistance of the resistor returns to at least the resistance value at ambient temperature. Heating in a heating cycle consisting of a heating pause period for a required time; and (5) a heating voltage of the resistor during a low-high temperature heating period of the resistor is changed to a low-peak voltage or current pulse; A high peak voltage or current pulse output immediately after the high voltage or current pulse, and (6) the heating power of the resistor during the low and high temperature heating period of the resistor is a sawtooth voltage or current. Or (7) an atmosphere sensor including a substrate having an adjacent, equal-sized cavity portion and an equal-resistance resistor arranged in series in a microbridge shape on the upper surface of the cavity portion. A clock circuit that oscillates a clock pulse that provides timing for simultaneously driving each of the resistors of the atmosphere sensor; a low-power pulse that heats one of the resistors at a low temperature in synchronization with the clock pulse; A drive circuit for outputting a high power pulse for heating at a high temperature; and a predetermined gas concentration calculating circuit for comparing a resistance value of the resistor heated at a high temperature with a resistance value heated at a low temperature to calculate a predetermined gas concentration according to the comparison value. And (8) the driving circuit includes:
Synchronously with the clock pulse of the clock circuit, the series-connected resistors are alternately heated and heated alternately without being heated or cooled at the same time. Things.

[0022]

[Function] When a resistor is heated at a constant power in an atmosphere for measuring a specific gas concentration, when the heating power is small, the resistance changes only by the ambient temperature without being affected by the specific gas concentration. The resistance value of the resistor is a function of the ambient temperature, and when the heating power is large, utilizing the fact that the resistance value of the resistor becomes a function of the ambient temperature and the specific gas concentration,
A resistor is arranged in a micro-bridge shape in a sealing cap having a mesh and continuously heated with a small power not affected by a specific gas concentration and a large power affected by a specific gas concentration, thereby forming a resistor. A specific gas concentration at the same place by the same resistor is calculated by subtracting the resistance value when the body is driven with low power from the resistance value when driving the body with high power.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an example in which an atmosphere meter according to the present invention is applied to a hygrometer will be described, but as described above, the present invention is not limited to a hygrometer. FIG. 1 is a diagram for explaining the principle of a hygrometer as an example of an atmosphere meter according to the present invention. The description will be made in comparison with the humidity measurement principle of a conventional hygrometer for easy understanding. In FIG. 1, white arrows (a ₁ ) → (b ₁ ) → (c ₁ ) → (d ₁ ) indicate humidity measurement according to the present invention, and (a ₁ ) → (b ₁ ), (a ₂ ) → (b) ₂ ) →
(B ₃ ) shows the flow of the conventional humidity measurement. FIG. 1 (a ₁ )
Is a structural diagram of a humidity detecting element, and FIG. 1 (a ₂ ) is a structural diagram of a temperature compensating element. In the drawing, 1 is a sealing cap, 2 is a mesh, 3 is a base, 4 is a hermetic seal, and 5, 6 are The lead pins 7 are resistors (referred to as detection elements).

The humidity detecting element shown in FIG. 1 (a ₁ ) has parallel lead pins 5 and 6 penetratingly disposed at a predetermined minute interval through a hermetic seal 4 on a base 3 made of a high heat conductive material.
A sealing cap 1 having a mesh 2 is fixed to a base 3 by welding a detection element 7 to the tip of the base 3. The detection element 7 has a positive temperature characteristic, for example, platinum, tungsten, nichrome, Kanthal, or a negative temperature coefficient, for example, SiC (silicon carbide), TaN
A fine temperature-sensitive element such as a fine wire or thin film such as (tantalum nitride) or a thermistor is connected.

The resistance value of the above-mentioned detecting element 7 changes according to the ambient temperature and humidity when heated at a low or high temperature, and its heat capacity is extremely small.
For this reason, the detection element 7 uses a micro temperature sensing element composed of a fine wire or a micro body in a micro bridge structure. When the heating element reaches a predetermined thermal equilibrium temperature in a very short time, and when the heating power is stopped, the surrounding area is immediately set. Try to return to the temperature.

The detecting element 7 of the temperature compensating element shown in FIG. 1 (a ₂ ) has the same standard as the detecting element 7 of the humidity detecting element, and is sealed with the humidity detecting element shown in FIG. 1 (a ₁ ). The detection element 7 is sealed by removing the mesh 2 of the cap 1. A conventional humidity detecting principle using the humidity detecting element shown in FIG. 1 (a ₁ ) having the above structure and the temperature compensating element shown in FIG. 1 (a ₂ ), and a conventional humidity detecting principle shown in FIG. 1 (a ₁ ). First, the humidity detection principle according to the present invention using only the humidity detection element will be described.

FIG. 2 (a), (b) is a voltage-current characteristic diagram of the humidity detecting element, FIGS. 2 (a) is a diagram showing the humidity characteristics, the humidity detection device of FIG. 1 (a ₁₎ , characteristic curve showing a voltage-current characteristic a ₂ (solid line) when the voltage-current characteristic a ₁ (dotted line) and 0 g / m ³ when the humidity is 200 g / m ³ at ambient temperature 30 ° C. constant, FIG. 2 (b ) is a diagram showing temperature characteristics, humidity 0 g / voltage-current characteristics at the temperature 20 ° C. in m ³ B ₁ (dotted line), the voltage-current characteristic B ₂ (solid line when the 30 ° C.), the voltage at the time of 40 ° C. In the characteristic curve showing the current characteristic B ₃ (dotted line), the horizontal axis represents the voltage applied to the detection element, and the vertical axis represents the current applied to the detection element.

In the voltage-current curve at 30 ° C. showing the humidity characteristic shown in FIG. 2A, the current applied to the humidity detecting element is 2 m.
The following small heating current A, the voltage and the A ₁ curve and A ₂ curve corresponding overlap substantially indicates about 0.8V or less, at the time of the low current heating, the temperature characteristics which is not affected by humidity shows only, in the large current detecting element applied current is 8 mA, a ₁ curve substantially 3V (volts), a ₂ curve shows an approximately 4V, the voltage generated in the detection element as humidity is large becomes small in a large current heating And a voltage corresponding to the humidity can be obtained.

Humidity 0 g / m showing the temperature characteristic shown in FIG.
^In the voltage-current curve in FIG. ^3, since there is no humidity around the detecting element, when a constant current, for example, 2 mA is applied to the detecting element, the voltage generated at both ends of the detecting element becomes the curve B ₁ ,
As shown in B ₂ and B ₃ , the higher the ambient temperature, the higher the temperature, and the lower the ambient temperature, the lower the temperature.

In FIG. 1, (b ₁ ), (b ₂ ), (b ₃ ),
Both (c ₁ ) and (d ₁ ) are absolute humidity (g / m ³ ) on the horizontal axis,
The vertical axis is a graph showing the output voltage (V). FIG. 1 (b
_1), the ambient temperature is 20 ° C. when applying a current of 8mA humidity sensing element 7 shown in FIG. 1 (a _1), 30 ° C., 40
Line B showing the relationship between absolute humidity and output voltage in ° C
_11, B is a diagram showing a ₁₂ and B _13, is in the negative proportional to the output voltage and the absolute humidity, is proportional to the ambient temperature.

On the other hand, in the temperature compensating element shown in FIG. 1 (a ₂ ), as shown in FIG. 1 (b ₂ ), the output voltage naturally changes in proportion to only the ambient temperature regardless of the absolute humidity. I do. Lines with ambient temperatures of 20 ° C, 30 ° C, and 40 ° C
_21, and B ₂₂ and B _23.

The output corresponding to the absolute humidity at the same ambient temperature is subtracted from FIGS. 1 (b ₁ ) and 1 (b ₂ ). Straight line B
₁₃ and B ₂₃ , B ₁₂ and B ₂₂ , and B ₁₁ and B ₂₁ , respectively. As shown in FIG. 1 (b ₃ ), the negative proportional relationship only to the absolute humidity is obtained regardless of the ambient temperature. related linear B ₃₃ of the absolute body moisture and the output voltage in the obtained.

In the hygrometer as an example of the atmosphere meter according to the present invention, when the detecting element 7 is driven at a low current, for example, 1 mA, the absolute humidity is affected as shown in FIGS. 2 (a) and 2 (b). Instead, an output voltage proportional to only the ambient humidity of 20 ° C., 30 ° C., and 40 ° C. is obtained, and parallel straight lines c ₁ , c ₂ , and c ₃ shown in FIG. 1 (c ₁ ) are obtained. This shows the same relationship as FIG. 1 (b ₂ ), and FIGS. 1 (c ₁ ) and 1 (b ₁ )
From the relationship, as shown in FIG. 1 (d ₁ ), FIG. 1 (b ₃ )
An output straight line B ₀ that is in a negative proportional relationship only with the absolute humidity equal to the characteristic is obtained.

In the above description, the case where the humidity detecting element according to the present invention is driven by a constant current has been described. However, since the heat capacity of the detecting element 7 is extremely small and the response is excellent, it is driven by a pulse current having a short time width. May be. Further, constant voltage or constant voltage pulse driving may be used.

FIG. 3 is a diagram for explaining a method of driving a humidity detecting element of a hygrometer as an example of an atmosphere meter according to the present invention. FIG. 3 (a ₁ ) shows a pulse current driving method, and FIG.
(A ₂ ) shows a pulse voltage driving method. That is, the hygrometer of the present invention has a humidity characteristic curve shown in FIG.
The drive pulse may be a constant current or a constant voltage as long as the drive is performed in accordance with the temperature characteristic curve. Figure 3 is the case of the constant current pulse driving shown in (a _1), a constant current pulse power supply 10
And the detecting element 11 are connected in series to detect the voltage Vout across the detecting element 11. In the pulse voltage driving method shown in FIG. 3A ₂ , the constant voltage pulse power supply 12 and the detection resistor 13
And the detection element 11 are connected in series to detect the voltage Vout across the detection resistor 13. In any case, the detecting element 11
In contrast, two types of constant current or constant voltage pulses having different temperature values during driving are applied.

[0036] FIG. 3 (b), a diagram showing an example of a current pulse train at FIG 3 (a ₁₎ a current pulse driving, while extending from time t ₁ to time t ₂ to detection element 11, a peak value 2m
A, a small pulse current having a pulse width of 50 ms (millisecond) is applied, and then, from time t ₂ to t ₃ , a peak value of 8 mA
Applies a large pulse current having a pulse width of 50 ms. Time t
_After a pause time of 100 ms from ₃ to t ₄ , it is driven again by a current pulse train of 2 mA and 8 mA small and large current pulses of the same time width.

FIG. 3C shows a voltage (Vou) generated between the detecting elements 11 by the current pulse driving shown in FIG.
This shows the voltage pulse train of t), and a voltage pulse with a time delay occurs at the rise of the current pulse. For this reason, it is necessary to perform voltage detection within the time width of c ₁ and c ₂ where the voltage value is stable. Incidentally, rest period between times t ₃ ~t ₄ of the drive current pulse train shown in FIG. 3 (b), after the pulse current application of 8 mA, chose time width heating temperature of the detection element 11 becomes substantially ambient temperature Things.

In FIG. 3B, a small current pulse and a large current pulse are continuously applied to the detecting element 11, but a large current is applied after a predetermined stabilization time has elapsed after the application of the small current. However, since a time delay occurs for each drive current pulse, high response cannot be detected. According to the driving method shown contrast in FIG. 3 (b), as shown by a dotted line d ₁ in FIG. 3 (d), due to the response of the output voltage when applying a large current pulse is small current driving Increased for preheating.

FIGS. 4A and 4B show a current pulse waveform and a voltage pulse output waveform when a large current pulse drive is continuously performed and a small current pulse current drive is performed.

That is, when driving is first performed with a large current pulse (8 mA) for detecting the temperature and humidity in the time width T ₁ , and then driven continuously with a small current pulse (2 mA) for detecting the temperature in the time width T _2. , the output voltage as shown in B ₁ in FIG. 4 (b), the time delay of the rising of the time of large current pulse driving is increased, similarly, as shown in B _2, greater time delay during falling Therefore, the output voltage stabilization time at the time of small current pulse driving becomes long, and detection with excellent responsiveness cannot be performed.

FIGS. 5 (a), 5 (b), 5 (c), and 5 (d) are diagrams for explaining the relationship between environmental changes and output characteristics of a hygrometer as an example of an atmosphere meter according to the present invention. 5 (a) is a temperature change on the time axis, FIG. 5 (b) is a humidity change on the time axis, FIG. 5 (c) is an applied current waveform, and FIG. 5 (d) corresponds to the above temperature change and humidity change. 5 shows a detected output voltage waveform due to the applied current.

The applied current is a continuous pulse current consisting of a small current pulse of 2 mA having a predetermined pause time and a large current pulse of 8 mA to be applied, and the pulse current is a time t _0.
It is output once during _{~t 1, t 1 ~t 2,} t 2 ~t 3. On the other hand, the temperature change is a constant temperature of 30 ° C. as shown in FIG.
Period of time t ₁ ~t ₂ from the 20 ℃, 30 ℃, 40
° C, and kept at 30 ° C during other periods. Also, changes in humidity in the period of constant humidity 20 g / m ³ from the time t ₂ ~t ₃ as shown in FIG. 5 (b) 10
g / m ³ or 30 g / m ³ .

[0043] Thus, in a period of time t ₀ ~t ₁ temperature, constant humidity both are changing only humidity for a period of time changes only the temperature t ₂ ~t ₃ during a period of time t ₁ ~t _2.

As a result, the detected output voltage waveform is shown in FIG.
Becomes an output voltage corresponding temperature, humidity constant at a period of time t ₀ ~t ₁ (d), the in the period of time t ₁ ~t _2, becomes an output voltage proportional only to the temperature and humidity constant, A subtraction value obtained by subtracting the output voltage at the time of the small current drive from the output voltage at the time of the large current drive becomes constant, and in this case, there is no influence of humidity. On the other hand, the time t _{2 at which} only the humidity changes
During the period of t ₃ , the output voltage at the time of small current drive is humidity,
, Is constant, and changes under the influence of humidity only at the time of large current driving. The output voltage at this time is low when the humidity is high, and is high when the humidity is low. Next, a description will be given based on a driving circuit that performs such an operation.

FIG. 6 is a block diagram showing an example of a driving circuit of a hygrometer as an example of an atmosphere meter according to the present invention. In the figure, reference numeral 15 denotes a circuit for supplying a constant current to a sensor (constant current circuit); Is a coefficient setting circuit, 17 is a hold circuit, 1
8 is a subtraction circuit, and 19 is an output terminal.

The amplifier circuit 15 is loaded with a series resistor of the detecting element 7 and a reference resistor R whose one end is grounded. The voltage of the reference resistor R supplies a constant current to the sensor (constant current circuit) 15. of which is fed back to an inverting input terminal, to the non-inverting input terminal a, the switch SW ₁ with b and c contacts are connected. The a contact of the switch SW _1, the reference voltage V _REF
The 1 and b contacts have V _REF 2 and the c contact are grounded, and the reference voltages V _REF 1 and V _REF 2 are V _REF 1 = 2R (mV) (1) V _REF 2 = 8R (mV) (2) Is set.

[0047] Further, the output end of the constant circuit for supplying a current to the sensor (constant current circuit) 15 a, the switch SW ₂ having a b-contact is connected to a contact, humidity temperature during low temperature heating A coefficient setting circuit 16 for setting a coefficient K for converting to an ambient temperature at the time of the calculation is connected, for example, a coefficient setting circuit 16 whose amplification degree is variable according to K is connected to one input terminal of a subtraction circuit 18 at the contact b. is, inputs the output voltage V _D at the time of a large current flows at the time of high temperature heating.

A switch SW ₃ having an a contact and a c contact and a hold circuit 17 are connected between the coefficient setting circuit 16 and the subtraction circuit 18. The a contact of the switch SW ₃ is connected to the hold circuit 17.

The switches SW ₁ , SW _2, and SW ₃ of the drive circuit configured as described above are interlocked, and the respective contacts a, b, and c of the switches SW ₁ , SW ₂ , and SW ₃ are simultaneously switched by switching. Can be When the contact is switched to the “a” contact, a voltage equal to the reference voltage V _REF 1 is applied to the reference resistor R connected to the inverting input terminal of the amplifier circuit 15, and 2 m is applied to the detecting element 7.
A constant current flows. Similarly, when the contact is switched to the contact b, a voltage equal to the reference voltage V _REF 2 is applied to the reference resistor R, and a constant current of 8 mA flows to the detection element 7.

FIG. 7 is a waveform diagram of each part of the drive circuit shown in FIG. 6. The operation of the drive circuit will be described below with reference to FIGS. The switch SW ₁ (SW ₂ and SW ₃ are also driven synchronously) is switched by the driving voltage pulses having the voltage waveforms of FIGS. 7A and 7B in the period from time t ₁ to t ₂ and from time t _{2 to} t ₃ , FIG. 7 (c) i
The drive currents 2 mA and 8 mA indicated by s flow. The a contact of the switch SW ₂ when it is switched to a contact point, the voltage Vs is output shown in FIG. 7 (d) in proportion to the ambient temperature.

The voltage Vs is input to the coefficient setting circuit 16 and is multiplied by a coefficient K set in advance, and a voltage V's (= KVs) shown in FIG. Switch SW ₂ is a
When switched to the contact point, the output voltage Vs is not a value that is correctly proportional to the ambient temperature, and is a coefficient for correcting the voltage Vs so as to correspond to the ambient temperature. K = (V _D −change in humidity) / Vs (3).

[0052] hold circuit 17, as shown in FIG. 7 (f), the "voltage V _D and V in. Subtraction circuit 18 for outputting s (= V's)" s Voltage V's equal V Enter and Figure 7
A voltage V proportional to the absolute humidity shown in (h) is output.
That is, V = V _D −V ″ s (4) is obtained.

FIG. 8 is a block diagram of a drive circuit for explaining another embodiment of a hygrometer as an example of an atmosphere meter according to the present invention. In FIG. 8, reference numeral 20 denotes a voltage detection circuit, and 21 denotes a current detection circuit. , 22 are division circuits, and portions having the same functions as in FIG. 6 are denoted by the same reference numerals as in FIG.

The drive circuit shown in FIG. 8 is a drive circuit for detecting humidity from a change in resistance of the detection element 7. That is, when the detection element 7 is driven with a small current and when driven with a large current, the voltage detector 20
Detects the voltage between both ends of the detecting element 7 and
On the other hand, the voltage across the reference resistor R having a known resistance value is detected by a current detector 21 and input to a division circuit 22, which calculates the resistance value of the detection element 7. Switch SW ₂ The following circuit is subtracted from the output voltage at the time of large current pulse driving humidity computing an output voltage at the time of a small current pulse driving based on the same principle as the drive circuit shown in FIG. 6 is performed.

FIGS. 9 (a) and 9 (b) show again the dual power supply driving method according to the present invention, and show the same driving current and output voltage waveform of the humidity detecting element as FIGS. 3 (b) and 3 (c). FIG. In the above description, when continuous 2 mA and 8 mA current pulse driving as shown in FIG.
Although a voltage output with a delay as shown in (b) is obtained, this drive method requires two highly accurate drive power supplies, and the accuracy and stability of the drive power supply are directly affected by the output voltage value. For example, different circuit components are required to obtain two peak current pulses of 2 mA and 8 mA, respectively, and the accuracy of the peak value depends on the characteristics of the components.

FIGS. 10A and 10B are diagrams showing an example of a drive current waveform and an output voltage waveform of a hygrometer as an example of an atmosphere meter according to the present invention, and show a time t shown in FIG. 10A.
When driven with a current of a triangular wave (sawtooth) which is proportional to the time within a predetermined time width from ₁ to t _2, and outputs the wake no output voltage time delay as shown in Figure 10 (b). But,
Similarly to the points P and C in FIG. 9B, in FIG. 10B, the voltage values at the time of the small current drive and the time of the large current drive are set at the measurement time indicated by the determined points P and Q. Is determined.
In this way, by driving with a triangular constant current source,
Only one power supply is required for driving, and the measurement can be performed with high accuracy. In measurement, measurement timings P and Q may be determined.

FIGS. 11A and 11B show other driving current waveforms of the detecting element of the hygrometer as an example of the atmosphere meter according to the present invention. FIG. 11A is a convexly curved approximate triangular current waveform in which the rate of change in current decreases with time, and FIG. 11B is a concave curve in which the rate of change in current changes with time. As long as the current waveform has an approximate triangular waveform and is a stable current source, the same effect as in the case of the triangular current driving of FIG. 10 can be obtained.

FIGS. 12 (a), 12 (b), 12 (c), 12 (d) and 12 (e) are timing charts for explaining the operation of a hygrometer driving circuit as an example of an atmosphere meter according to the present invention. FIG.
(A) is a low / high temperature voltage waveform output during the low / high temperature driving period,
FIG. 12B shows an output voltage waveform at the time of sawtooth wave driving.
(C) is a clock pulse, and FIG. 12 (d) is measurement ON / O.
FIG. 12E shows the FF signal, and FIG. 12E shows the reset signal.

In FIG. 3 (c) and FIG. 9 (b), P and Q define voltage measurement timings when the output voltage is stabilized. The measurement timing tb is uniquely determined if the timing t ₀ for heating and driving the detection element 7 is determined.
High / low temperature voltage waveform or (b) sawtooth voltage waveform and dotted line A
Time to a point where the -A line changes t _a and the dotted line B-B
Low hot voltage is measured at the time t _b until the point b changes the line.

The low-high-temperature driving time t ₁ and the driving suspension time t ₂ are determined by the (d) measurement ON / OFF signal. At the time t ₁ at which the low-high temperature driving is completed, (e) a reset signal is output. You. However, these times t _a , t _b , t
₁ and t ₂ are determined by measuring (c) the number of clock pulses.

FIG. 13 is a block diagram of an example of a timing generation diagram according to the present invention. In FIG. 13, reference numeral 20 denotes a clock generation circuit, 21a, 21b, and 21c denote counters and a circuit 22 reference voltage generation circuit.

FIG. 12C shows the state of the clock generation circuit 20.
Is generated, and the counter circuit 21a
In the example, when a preset number of pulses corresponding to the time ta is reached, the measurement timing pulse a is output.
From the counter circuit 21b, is output measurement timing pulses b when it reaches the number of pulses corresponding to the time t _b.
Further, the counter circuit 21c, and outputs a pulse corresponding to the measured ON / OFF signal low high thermal drive time t ₁ and the drive downtime t _2, the pulse by the counter circuit 21a at time t _1, reset 21b, and 21c and to open the pulse from the counter circuit 21a, the counter gate of 21b at time t _2. When the counter 21c is reset, the reference voltage generation circuit 22 outputs a reference voltage E for driving the detection element.

FIG. 14 is an example of a reset circuit, and FIG.
15 shows a time chart of the reset circuit of FIG. DF
FIG. 15 is connected to the D input terminal of the F (delay flip-flop) 23.
(B). When the measurement ON / OFF signal is input,
The Q shown in FIG. 15C corresponding to the ON / OFF signal is output with a delay of one clock pulse. The reset signal of FIG. 15D having the clock pulse width is output as an AND output between the clock pulse of FIG. 15B and the output Q.

FIG. 16 is a block circuit showing an example of a saw-tooth wave current drive circuit for driving a detection element according to the present invention.
Includes a resistor R ₀ which receives reference voltage E, the resistance R ₀ and the feedback capacitor C ₀ and O-P amplifier 26. Switch 27 des charges the feedback capacitor C ₀ by the integrating circuit reset signal consisting of a reset A saw-tooth voltage V ₁ proportional to time t is output within a period determined by the signal. _{V 1 = (E / C O} R O) t (5)

The voltage V ₁ is equal to the input resistance R which is the same as the reference resistance R _S.
The current is input to a constant current circuit composed of an OP amplifier 28 having _a , and a sawtooth-shaped constant current i proportional to the voltage V ₁ flows to the detection element. That is, from (5)

[0066]

(Equation 1)

Is obtained.

FIG. 17 is a block circuit diagram for explaining an embodiment of a humidity output circuit using a sawtooth wave current drive of the detection element according to the present invention. In the figure, reference numerals 29 and 30 denote amplification circuits, and 31 denotes an amplification circuit. Coefficient setting circuit, 32 and 33 are hold circuits,
34 is a subtraction circuit.

The sawtooth-shaped constant current i shown in FIG. 16 flows through the detecting element 7, and the voltage between both ends of the detecting element 7 is input to the amplifier circuits 29 and 30 connected in parallel. Amplifier circuit 2
9 and the coefficient setting circuit 31 and hold circuit 32 in which measuring the output voltage V _s of the low current drive is the column connection. On the other hand, the amplifier circuit 30 outputs the output voltage V _D at the time of high current driving.
And a hold circuit 33 is connected.

[0070] hold circuit 32 holds the correction voltage V _'s measurement timing pulse a after multiplied by a coefficient K to the output voltage V _s of the time of small current drive. On the other hand, the hold circuit 33 holds the measuring timing pulse b output voltage V _D at the time of large current driving.

The small current held by the hold circuit 32
Output voltage V during driving_S”(= V_S′) And the hold circuit 33
Output voltage V at the time of large current driving held at_DSubtracts
The voltage V which is subtracted by the circuit 34 and is proportional to the absolute humidity is output.
It is. It should be noted that the low-temperature small current drive current was 2 mA,
Assuming a large current driving current of 8 mA, t = T according to the equation (6). _a
2mA, t = t_bThe circuit is set to 8 mA when
Constant C_O, R_O, R_SAnd E may be determined.

FIG. 18 is a block diagram for explaining another embodiment of a humidity output circuit using a saw-tooth wave current driver of the detecting element according to the present invention. In FIG. Denotes a CPU (Central Processing Unit).
13 and 17 are denoted by the same reference numerals as in FIGS.

The humidity output circuit shown in FIG. 18 uses the clock of the CPU 37 for the timing pulse, that is, the measurement ON / OFF signal and the measurement timings t _a and t _b reset signals. Further, since the CPU 37 has a storage function, a special hold circuit for holding the output voltage at the time of low temperature and at the time of high temperature is unnecessary. Therefore, the output voltage of the detection element 7 is amplified to a predetermined voltage by the
The digital value of the detected voltage converted by the D converter 36 is read and stored at the timing of the measurement timings t _a and t _b by the CPU 37, and the coefficient is set. You can ask.

FIG. 19 is a diagram for explaining an embodiment of a humidity output circuit when the detecting element according to the present invention is driven by a voltage pulse. In the drawing, reference numeral 38a denotes reference voltage generating circuits 1 and 38b.
1 is a reference voltage generating circuit 2 and 39 is a constant voltage circuit.
Portions that operate the same as in FIG. 8 are given the same reference numerals as in FIG.

The reference voltage generating circuit 1 shown at 38a is a constant voltage circuit for applying a low voltage V _REF 1 to the detecting element 7, and the reference voltage generating circuit 2 shown at 38b is a constant voltage circuit.
A constant voltage circuit that applies a high voltage V _REF 2 to each other. Each constant voltage circuit includes an a contact, a b contact, and a grounded c contact driven by a timing pulse output from a terminal P _{01 of} the CPU 37. It is connected to a contact and b-contact of the switch SW ₁ having the switch SW ₁ is connected to the non-inverting input of the constant voltage circuit 39.

The constant voltage circuit 39 loads a series resistance of the reference resistance Rs and the detection element 7 whose other end is grounded, and the connection point is connected to the inverting input. Voltage Vs between the sensing element 7 in the constant voltage circuit 39 of the circuit arrangement is the respective voltage equal to the voltage applied to the contacts of the switch SW _1. That is, the switch SW ₁ is a constant voltage of Vs = 0 when Vs = V _REF 2 c contacts when Vs = V _REF 1 b contacts when a contact is output.

As described above, when the voltage Vs of the detection element 7 having the resistance value Rs is constant, the current is flowing through the reference resistance Rr is i
s = Vs / Rs, and a current corresponding to the resistance Rs flows through the detection element 7. That is, when the resistance Rs changes due to temperature or humidity, the current is also changed accordingly, and the amplifier circuit 35 detects the current is flowing through the reference resistance Rr as the voltage Vr (= is · Rr).

FIG. 20 is a time chart showing an example of FIG. 19. For example, V _REF 1 = 0.5 V, V _REF 2 = 4.5 V
Then, the time t ₁ when the switch SW ₁ is connected to the contact a is
, Vs = 0.5 V, time t ₂ connected to contact b
Vs = 4.5V becomes the period, the period of time that is connected to the contact c t ₃ is similar timing settings and during the constant current heating shown in FIG. 6 is performed. That is, the low-temperature heating in which SW ₁ is connected to the a contact corresponds to a constant current drive of 2 mA,
_The low-temperature heating in which ₂ is connected to the b-contact is the same as in the case of driving at a constant current of 8 mA.

FIG. 21 is a perspective view for explaining another embodiment of a humidity sensor of a hygrometer as an example of an atmosphere meter according to the present invention. In FIG. 21, reference numeral 40 denotes a silicon substrate;
42 is a cavity, 43 and 44 are oxide film substrates, 45 and 46 are resistors, and A, B and C are electrodes.

[0080] humidity sensing element illustrated in FIG. 1 (a ₁₎ is
As described above, one detecting element 7 which is a resistor having a microbridge structure is provided, and one detecting element 7 is continuously heated at a low temperature and a high temperature every 50 ms, for example. In reality, the surrounding environment does not change abruptly within such a short time, but ideally, it is sufficient if the detection element 7 can be simultaneously driven at low and high temperatures to detect a difference in resistance value. However, it is impossible to perform low-temperature and high-temperature heating at the same place and at the same time. FIG. 21 shows another embodiment of the humidity sensor according to the present invention, in which two resistors are arranged as close as possible to one another so as not to affect each other.

The humidity sensor shown in FIG.
a supporting arms 43a to 43d and 44a to 44d
The hollow portions 41 and 42 having the same shape and the same shape are formed, leaving the oxide film substrates 45 and 46 supported by the above-mentioned steps, and the fine structure having a zigzag structure is formed on the oxide film substrates 45 and 46 formed on the hollow portions 41 and 42. Resistors 45 and 46 having a width are connected in series, a connection portion is used as an electrode B, and the other ends are used as electrodes A and C, respectively. At this time, the package of the crystalline silicon substrate 40 uses a gas-permeable mesh cap instead of a sealing cap. Next, the operation of the humidity sensor having the above-described structure will be described.

FIGS. 22 (a) and 22 (b) to (d) show FIGS.
5 is a time chart for obtaining humidity using the humidity sensor shown in FIG. FIG. 22A shows a clock circuit (not shown).
Clock pulses a ₁ , a ₂ , a ₃ ... Transmitted at equal time intervals with equal intervals are shown. FIG.
(B) shows low-temperature heating with low-peak power pulses b ₁ , b ₂ , b ₃ for heating the resistor 46 between the terminals C, B in synchronization with the clock pulses a ₁ , a ₂ , a ₃ . , The resistance value of the resistor 46 proportional to the temperature is detected.

At the same time, clock pulses a ₁ , a ₂ , a ₃ ...
.., Which heats the resistor 45 between the terminals B and A in synchronism with the high-temperature power pulses c ₁ , c ₂ , c ₃ ..., And detects the resistance value of the resistor 46 proportional to the temperature and humidity. .

FIG. 22D shows the result of subtracting the resistance value of the resistor 46 heated at a low temperature from the resistance value of the resistor 45 heated at a high temperature by a humidity operation circuit (not shown) to obtain clock pulses a ₁ , a ₂ and a. _The humidity pulses d ₁ , d ₂ , d _3, ... Having a peak value in proportion to the humidity in synchronization with ₃ .

FIGS. 23 (a), 23 (b) and 23 (c) show other time charts for obtaining the humidity using the humidity sensor shown in FIG. The clock pulses a ₁ , a ₂ , a ₃ ... Shown in FIG. 23A have the same intervals as the clock pulses a ₁ , a ₂ , a ₃ . Are driven in synchronization with the clock pulses a ₁ , a ₂ , a ₃ .

For this reason, the driving method of the time chart of FIG. 23 is a time chart obtained by further improving the driving method of FIG. 22, and the low-temperature-side resistors 46 are also operated alternately at a high temperature. The resistor 45 is operated at a low temperature, and the temperature detection and the temperature / humidity detection are performed alternately.

That is, when the resistor 46 between the terminals B and C synchronized with the clock pulse (a ₁ ) is heated at a low temperature by the power pulse b ₁ , the resistor 45 between the terminals B and A becomes the power pulse c
Heat to ₁ at high temperature. At the timing of the clock pulse a ₁ , the humidity pulse (not shown) calculates the resistance value difference of the resistor at the time of driving the b ₁ pulse that represents only the temperature from the c ₁ pulse that represents the temperature and humidity. the _second timing, detects the humidity based on the resistance value difference at high power pulse drive time and low power pulses at the time of driving the pulse b _1.

[0088]

As apparent from the above description, the following effects can be obtained according to the present invention. (1) Effects on Claims 1 to 6: (a) For individual variations of the sensing element: In the conventional atmosphere meter in which the sensing element and the compensation element are separately combined, the resistance value (VI) of each sensing element is used. If the characteristic) and the temperature coefficient of resistance do not match, use in a wide temperature range can be prevented, or higher-precision detection performance cannot be obtained. Therefore, a strict combination of characteristics is required, which results in an increase in cost in terms of mass productivity, yield, and the number of steps. However, in the present invention, since the same detection element performs compensation and detection, the resistance value (V -I characteristic) and the temperature coefficient of resistance are the same, so that high-accuracy performance can be obtained even if individual detection elements vary. (B) Variation in individual response time (rise time) of the detection elements: When two conventional detection elements are combined, the response time varies, but in the present invention, the same detection element is used. If the temperature detection is slow, the detection of the predetermined gas concentration is also slow, and the response time is always in a fixed relationship, and there is no difficulty in combination. (C) For the variation with time of individual detection elements:
In the two conventional detection elements, changes with time are slightly different from each other, so that only the matching time can be used, but after that period, the two detection elements cannot be used. It was also difficult to predict the period or to self-detect the period. However, in the present invention, there is no problem because the elements are the same and have a certain relationship according to a change in characteristics. Therefore, even if the aging characteristics of the device vary, the device can be used if the aging variation of the device itself is not extremely large. (D) With respect to the influence of humidity on the sealing cap: In a conventional atmosphere meter having a compensating element, when a gas having a different concentration is applied to the sealing cap, a very small amount of the sealed air is conducted to generate heat inside the sealing cap. Although the output appears on the body and the influence of different gas concentrations appears, it is not possible to accurately take out the gas concentration fluctuations. However, in the present invention, only one detection element is used, and both gas concentration measurement and gas concentration and ambient temperature measurement are performed. In both cases, since the state of the cap and the state of the surrounding atmosphere are the same, there is no influence of the gas concentration. (E) With respect to power consumption: In a densitometer using a conventional compensating element, power consumption was required to be approximately twice that of a detecting element. The power is several tenths of the power, and the total power consumption is about half. (F) Pressure fluctuation: Unlike the case where the temperature is compensated by the steady pressure of the sealing cap, the ambient pressure of the temperature compensation is almost the same as that at the time of detection, so that there is no deviation of the measured value due to the pressure fluctuation and high accuracy. (2) Effect on Claim 7: Gas concentration can be measured at the same time even for a sudden change in the surrounding environment. (3) Effect on Claim 8: When the two resistors are alternately driven with different driving power pulses, the following effects are also added. (A) The durability life is simply doubled. (B) The heat accumulation on the temperature gas concentration detection side is reduced, the operation interval can be reduced, and the application is expanded. (C) The power applied to the power supply during energization is uniform and stable. (D) Since it is made using the integrated circuit technology, there is little variation between the two components, and this is easy to realize.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining the principle of a hygrometer as an example of an atmosphere meter according to the present invention.

FIG. 2 is a voltage-current characteristic diagram of a humidity detecting element.

FIG. 3 is a diagram for explaining a humidity detection element driving method of a hygrometer as an example of an atmosphere meter according to the present invention.

FIG. 4 shows a current pulse waveform and a voltage pulse output waveform when a large current pulse drive is continuously performed and a small current pulse current drive is performed.

FIG. 5 is a diagram for explaining the relationship between environmental changes and output characteristics of a hygrometer as an example of an atmosphere meter according to the present invention.

FIG. 6 is a block diagram showing an example of a driving circuit of a hygrometer as an example of an atmosphere meter according to the present invention.

FIG. 7 is a waveform chart in each part of the drive circuit shown in FIG. 6;

FIG. 8 is a drive circuit block diagram for explaining another embodiment of a hygrometer as an example of an atmosphere meter according to the present invention.

FIG. 9 is a re-presentation of the dual power supply driving method according to the present invention.

FIG. 10 is a diagram showing an example of a drive current waveform and an output voltage waveform of a hygrometer as an example of an atmosphere meter according to the present invention.

FIG. 11 is a diagram showing another drive current waveform of the detection element of the hygrometer as an example of the atmosphere meter according to the present invention.

FIG. 12 is a timing chart for explaining an operation of a drive circuit of a hygrometer as an example of an atmosphere meter according to the present invention.

FIG. 13 is a block diagram of an example of a timing generation diagram according to the present invention.

FIG. 14 is a diagram illustrating an example of a reset circuit.

FIG. 15 is a diagram showing a time chart of the reset circuit of FIG. 14;

FIG. 16 is a block circuit showing an example of a saw-tooth wave current drive circuit of the detection element according to the present invention.

FIG. 17 is a block circuit diagram for explaining an embodiment of a humidity output circuit based on sawtooth current drive of the detection element according to the present invention.

FIG. 18 is a block diagram for explaining another embodiment of the humidity output circuit based on the sawtooth current drive of the detection element according to the present invention.

FIG. 19 is a diagram for explaining an embodiment of a humidity output circuit when the detection element according to the present invention is driven by a voltage pulse.

FIG. 20 is a time chart of one example of FIG. 19;

FIG. 21 is a perspective view for explaining another embodiment of the humidity sensor of the hygrometer as an example of the atmosphere meter according to the present invention.

FIG. 22 is a time chart for obtaining humidity by using the humidity sensor shown in FIG. 21.

23 shows another time chart for obtaining humidity by using the humidity sensor shown in FIG. 21.

FIG. 24 is a partial sectional view showing the structure of a conventional hygrometer.

FIG. 25 is a diagram for explaining the occurrence of a detection error due to a response delay in atmospheric temperature detection of a conventional hygrometer.

FIG. 26 is a diagram showing another conventional hygrometer.

FIG. 27 is a view showing the structure of still another conventional hygrometer.

28 is a circuit configuration example of the hygrometer shown in FIG. 27.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Sealing cap, 2 ... Mesh, 3 ... Base, 4 ... Hermetic seal, 5 ... Lead pin, 7 ... Resistor (detection element), 15 ... Amplifier circuit, 16 ... Coefficient setting circuit,
17 Hold circuit, 18 Subtractor, 19 Output terminal, 20 Voltage detection circuit, 21 Current detection circuit, 22
Division circuit, 23: DF / F (delay flip-flop), 26: OP amplifier, 27: switch, 29, 3
0: amplification circuit, 31: coefficient setting circuit, 32, 33: hold circuit, 34: subtraction circuit, 36: A / D converter,
37 CPU (Central Processing Unit), 38a Reference voltage generating circuit 1, 38b Reference voltage generating circuit 2, 39 Constant voltage circuit, 40 Silicon substrate, 41, 42 Hollow part, 4
3, 44: oxide film substrate, 45, 46: resistor, A, B, C
…electrode.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01N 27/00-27/24 G01N 25/64 G01F 1/68-1/699

Claims (8)

(57) [Claims] 1. An atmosphere meter for detecting a predetermined gas in an atmosphere based on a change in the resistance value of the resistor heated in the atmosphere, wherein the resistor has a low temperature in which the resistance change is affected only by the atmosphere temperature. A low-temperature drive circuit for heating with
A high-temperature drive circuit for heating the resistor at a high temperature where the resistance change is sensitive to the temperature of the atmosphere and a predetermined gas; and a comparison detection circuit for comparing a high-temperature voltage generated between both ends of the resistor with a low-temperature voltage. An atmosphere meter for detecting a concentration of a predetermined gas contained in the atmosphere according to an output voltage of a comparison detection circuit. 2. A measurement ON / OFF signal generation circuit for determining a low / high temperature heating period and a heating pause period, a reference power generation circuit for heating a resistor in synchronization with the low / high temperature heating period,
A time measurement circuit that determines a read timing for reading the resistance of the resistor as a voltage during low-temperature heating and high-temperature heating in synchronization with the low-high temperature heating period; and a voltage generated in the resistor in synchronization with the resistance value reading timing. A voltage measuring circuit for reading, a coefficient setting circuit for setting and multiplying a coefficient for correcting a voltage generated in the resistor during low-temperature heating to be a voltage corresponding to the ambient temperature and outputting a correction voltage, and a memory for storing the correction voltage And a subtraction circuit for subtracting the stored correction voltage from a voltage generated in the resistor during the high-temperature heating, wherein a predetermined gas concentration in the atmosphere is obtained in proportion to an output of the subtraction circuit. The atmosphere meter according to claim 1, wherein 3. A micro-bridge having a thin wire having a heat-generating action of generating heat by applying electric power and having both ends of the thin wire insulated and held in a measurement gas via conductive pins. The atmosphere meter according to claim 1 or 2, wherein 4. A heating system comprising a low-high temperature heating period in which the resistor is heated at low and high temperatures, and a heating pause period in which a time required for the resistance of the resistor to return to a resistance value at least at an ambient temperature after the heating period. The atmosphere meter according to any one of claims 1 to 3, wherein heating is performed in a cycle. 5. A low peak voltage or current pulse, and a high peak voltage or current output immediately after the low peak voltage or current pulse, the heating power of the resistor during the low high temperature heating period of the resistor. The atmosphere meter according to any one of claims 1 to 4, wherein the atmosphere meter is a pulse. 6. The atmosphere meter according to claim 1, wherein the heating power of the resistor during the period of heating the resistor at a low temperature and a high temperature is a sawtooth voltage or a current. 7. A substrate having adjacent equal-sized and equal-sized cavities, and an atmosphere sensor having an equal-resistance resistor arranged in series on the upper surface of the cavities and connected in a microbridge shape;
A clock circuit that oscillates a clock pulse that gives timing for simultaneously driving each resistor of the atmosphere sensor;
A drive circuit for outputting a low-power pulse for heating one of the resistors at a low temperature and a high-power pulse for heating the other at a high temperature in synchronization with the clock pulse; a high-temperature heated resistor and a low-temperature heated resistor of the resistor; An atmosphere meter comprising a predetermined gas concentration calculation circuit for comparing values and calculating a predetermined gas concentration according to the comparison value. 8. The driving circuit alternately performs high-temperature heating and low-temperature heating in synchronization with a clock pulse of a clock circuit, without simultaneously heating or serially heating the series-connected resistors. The atmosphere meter according to claim 7, wherein the atmosphere meter is driven back.