JP5316219B2 - Dynamic characteristic measuring device that supplies a precise voltage to measure a specimen - Google Patents

Description

  The present invention relates to a dynamic characteristic measuring apparatus for measuring a plurality of specimens by supplying a precise voltage.

A sensor using a strain gauge incorporated in a bridge circuit is widely used when mechanically measuring a physical physical quantity such as a load, pressure, torque, or acceleration.
As an example of such a converter, as disclosed in Patent Document 1, a diaphragm for pressure detection formed on one surface side of a semiconductor substrate, and a plurality of resistance values that are arranged on the diaphragm and change in resistance value due to a piezoresistance effect. A semiconductor pressure sensor having a gauge resistance is known.

In addition, as in Patent Document 2, a metal substrate, two pairs of strain gauges having different pressure output characteristics formed on the substrate, and each strain gauge having the same pressure output characteristics are connected by connecting these strain gauges. 2. Description of the Related Art A surface pressure sensor is known that includes a wiring portion that forms a bridge circuit disposed on opposite sides. These sensors are not limited to those disclosed in Patent Documents 1 and 2, and many sensors using strain gauges incorporated in a bridge circuit are known.
Such a sensor is measured as a specimen (a name when a measurement object is used for a test) before shipment, and one product is measured by one precision power source and one precision voltage measuring instrument. When measuring a large number of specimens, a large number of precision power supplies and a large number of precision voltage measuring instruments are required, which entails huge equipment costs.

  Further, as can be seen in Patent Document 3, the process of measuring the strain by eliminating the influence of the resistance value of the lead wire for incorporating the strain gauge into the bridge circuit can be automatically and efficiently performed with a simple configuration. 2. Description of the Related Art A strain measurement system based on the 1-gauge 3-wire method is known that includes a switch circuit and has a simplified circuit configuration. However, if a switch circuit is used, the voltage may fluctuate greatly at the time of switching, which is inappropriate when a precise power source and a precision voltage measuring instrument are used to supply and measure an accurate voltage. It was.

JP 2002-39888 A JP-A-8-159893 JP-A-11-183112

  In view of the above problems, the present invention provides a dynamic characteristic measuring apparatus that supplies and measures a precise voltage to a plurality of specimens.

In order to solve the above-mentioned problems, the invention of claim 1 provides an output voltage (V) of a specimen (1) including a precision power source (10) for supplying a constant voltage (E), a strain gauge and a bridge circuit. A measuring instrument (20) for measuring, supplying a constant voltage (E) from the precision power source to the power supply voltage terminals (X1, X2) of the bridge circuit to the specimen (1), and a strain gauge In the dynamic characteristic measurement device that dynamically measures the output voltage of the bridge circuit while continuously changing the external force applied to the
The wiring connecting the output terminals (−, +) of the precision power supply (10) and the power supply voltage terminals (X1, X2) of the specimen (1) is branched in the middle, and the wirings have the same resistance. the wire and be Rukoto, one of the precision power supply (10) is, with respect to the supply voltage terminals of the plurality of the specimen (1) (X1, X2), so that it is possible to supply a constant voltage (E) to,
4 terminals further connecting the detection terminals (-S, + S) of the precision power supply (10) to the power supply voltage terminals (X1, X2) of one of the specimens (1) of the plurality of specimens (1) It is a dynamic characteristic measuring device by the method .

  Thereby, when measuring the dynamic characteristics of a specimen, a large number of specimens can be efficiently measured with a single precision power source. In addition, by inspecting a large number of products at the same time with the aim of reducing equipment costs, speeding up (reducing machine time) can be realized, and the cost of inspection equipment can be greatly reduced.

In addition, the voltage fluctuation caused by the load resistance fluctuation is detected, and the power supply side corrects the voltage, whereby an accurate power supply can be supplied.

The invention of claim 2 is the invention of claim 1 , wherein the specimen (1) is an intake pressure sensor, and a plurality of the intake pressure sensors are arranged in a pressure chamber (30), and the pressure is measured. The output voltage of the bridge circuit of the intake pressure sensor is dynamically measured while continuously changing the pressure in the chamber (30).

A third aspect of the invention is characterized in that, in the invention of the first or second aspect , the bridge circuit of the specimen (1) is constituted by a strain gauge of a 4-gauge method.

  In addition, the code | symbol attached | subjected above is an example which shows a corresponding relationship with the specific embodiment as described in embodiment mentioned later.

It is explanatory drawing which shows the relationship between a test body and bridge voltage, (a) shows the state at the time of no pressure to a strain gauge, (b) shows the state at the time of pressure application. It is explanatory drawing explaining the measuring method of the 1st comparison technique used as the foundation of this invention. It is a figure which shows the connection method of the test body of 1st comparative technique, and a precision power supply. It is a figure which shows the fluctuation | variation of the setting pressure of a pressure controller in the case of measuring the static characteristic of a 1st comparison technique. It is explanatory drawing explaining the dynamic characteristic measuring system of a 2nd comparison technique. In one Embodiment of this invention, it is explanatory drawing which electrically connects a precision power supply.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. About each embodiment, the same code | symbol is attached | subjected to the part of the same structure, and the description is abbreviate | omitted. In each embodiment of the present invention, parts having the same configuration are denoted by the same reference numerals with respect to the comparative technique on which the present invention is based, and the description thereof is omitted.

Sensors using strain gauges built into the bridge circuit are widely used to electrically measure mechanical physical quantities (external forces) such as load, pressure, torque, or acceleration. A bridge circuit of a pressure sensor such as a sensor (semiconductor pressure sensor or the like) will be briefly described.
1A and 1B are explanatory views showing the relationship between the specimen and the bridge voltage. FIG. 1A shows a state when no pressure is applied to the strain gauge, and FIG. 1B shows a state when pressure is applied. There are a 1 gauge method, a 2 gauge method, a 4 gauge method, and the like as a method of inserting a strain gauge into the bridge circuit. Here, a 4-gauge method will be described as an example. The resistance value change due to the strain of the strain gauges G1 to G4 is extremely small, and this is taken out as a voltage change using a Wheatstone bridge circuit (bridge circuit). The output voltage can be doubled by taking out the strain gauge (each gauge method).

In FIG. 1, R is a bridge resistance of the strain gauges G1 to G4, and ΔR is a bridge resistance change amount when a pressure is applied (the strain gauges G1 and G3 and the strain gauges G2 and G4 are subjected to strains having opposite signs). E) is a bridge power supply voltage (predetermined constant voltage) between the terminals X1 and X2, and V is an output voltage between the terminals Y1 and Y2 to be measured.
In this case, the output voltage V is expressed by the following equation.

  V = (ΔR / R) * E

  As shown in this equation, it can be seen that the error of the bridge power supply voltage E becomes the error of the output voltage V to be measured. This is not limited to the 4-gauge method, and the same applies to other gauge methods. Therefore, in order to inspect the accuracy of the sensor as the specimen, it is necessary to supply an accurate voltage to the bridge power supply voltage E with a precision power supply.

  Here, the precision power supply 10 is not particularly limited, and is a precision power supply in the sense that the precision is higher by one to two digits than a known low-cost power supply. The assumed accuracy is preferably a power supply having a resolution of about six and a half digits. For example, it indicates a power supply capable of supplying a voltage with an accuracy of about 10 μV in the 10 V range. As an example, a constant voltage power source that negatively feeds back the output voltage and accurately controls the voltage setting value can be cited as an object of the precision power source. A dropper regulation type analog constant voltage power source, a series regulation type analog constant voltage power source, a PWM type digital constant voltage power source and the like are preferable.

FIG. 2 is an explanatory diagram for explaining the measurement method of the first comparative technique that is the basis of the present invention. FIG. 3 is a diagram showing a method for connecting a specimen of a comparative technique and a precision power source. FIG. 4 is a diagram illustrating fluctuations in the set pressure of the pressure controller when the static characteristics of the first comparative technique are measured.
The specimen 1 is, for example, an intake pressure sensor, and a large number of specimens 1 are arranged in the pressure chamber 30 for measurement. The pressure chamber 30 can be set to a predetermined set pressure by a pressure controller 32 (not shown) through a conduit 31.

  As shown in FIG. 3, when a precise voltage is supplied, a method using a four-terminal method (four terminals of output terminal-, +, detection terminal -S, + S in FIG. 3) is effective. In the case of the two-terminal connection method, the connection path to the power source and the connection path of the measuring instrument are shared. When a power source current flows through this common connection path, a voltage drop occurs, resulting in a measurement error. In order to avoid this, a four-terminal method has been devised. In the four-terminal method, voltage fluctuations caused by load resistance fluctuations are detected at the detection terminals -S and + S terminals in FIG. 3, and the power supply side corrects the voltage, whereby accurate power can be supplied. In the first comparative technique shown in FIG. 2, one precision power supply is used for each specimen so that four terminals are configured, and one product is used for each precision power supply and one precision voltage measurement. I was measuring with the instrument. For this reason, when the production volume of the product becomes n times, n precision power supplies 10 (11, 12,...) And n precision voltage measuring instruments 20 (21, 22,. The equipment cost became necessary.

  In the case of static characteristic measurement in which the inside of the pressure chamber 30 is maintained at several predetermined set pressures (inspections I to III in FIG. 4) and the specimen 1 is inspected, the pressure fluctuation at the set pressure of the pressure controller is illustrated in FIG. 4. It takes a considerable amount of time to stabilize to the predetermined set pressure. For n products, it is conceivable to measure a large number of static characteristics with one precision power supply and one precision voltage measuring instrument using a switch composed of relays, etc., but after switching Therefore, it was impossible to measure efficiently.

On the other hand, as a second comparative technique, a dynamic characteristic measurement method is considered. FIG. 5 is an explanatory diagram for explaining the dynamic characteristic measurement method of the second comparative technique. The inside of the pressure chamber 30 is changed from a high pressure to a low pressure, and the output voltage V when passing through several predetermined set pressures is measured (inspections I to III in FIG. 5), and the specimen 1 is inspected.
According to this method, not only high-speed measurement can be performed, but also a highly accurate pressure controller is not required. However, this method can be applied only to a single specimen 1 for the following reasons.

  When measuring the dynamic characteristics of the specimen 1, it is necessary to electrically connect a precision power source and a precision power source measuring instrument. At this time, when measuring a large number of specimens 1 with a single precision power supply and precision power supply measuring instrument, even if an attempt is made to insert a switching device composed of a relay or the like, the disturbance generated at the time of switching becomes an error and is accurate. Cannot measure. In particular, the precision power supply takes a long time to correct voltage fluctuations due to disturbances in order to achieve precision.

  That is, at the time of switching, the resistance viewed from the specimen changes from a resistance value unique to the connected device (power supply, measuring instrument) to a disconnected state (several tens to several hundreds MΩ). This change causes a signal disturbance to the specimen. In the case of a power supply, the output resistance peculiar to equipment is as small as several Ω, but in the case of a measuring instrument, the input resistance is as large as several hundred MΩ, so in the case of a power supply, a large resistance change occurs. There will be little resistance value change. In other words, the power supply is greatly affected. Furthermore, the required stability increases as the precision of the power supply increases, so that a longer stabilization time is required, and insertion of a switching device becomes increasingly unsuitable for dynamic measurement.

In one embodiment of the present invention, the following configuration is adopted to solve such a problem.
FIG. 6 is an explanatory diagram for electrically connecting a precision power supply in an embodiment of the present invention. A case where there are two specimens 1 (1-1, 1-2) will be described. The specimen 1 is a semiconductor pressure sensor such as an intake pressure sensor. In order to supply the power supply voltage E to the bridge circuit of the specimen 1, the precision power supply 11 is connected and the dynamic characteristics of the specimen 1 are measured.
First, two sets of electric wires having the same resistance, a total of four lines, a line AC, a line AE, a line BD, and a line BF, are prepared. The four electric wires are manufactured in the shortest range as long as wiring to the specimens 1-1 and 1-2 is possible. The resistance between the lines A and C = the resistance between the lines A and E, and the resistance between the lines B and D = the resistance between the lines BF. Even if there is a difference in resistance value between the lines, it is preferable that the resistance value is within about 1 mΩ.

  Using these four electric wires, the common potential points A (−) and B (+) are formed. At the common potential points A and B, the lines are joined by brazing or connecting metal fittings. The line A-C and the line A-E are connected to the negative terminals C and E (X2) of the specimens 1-1 and 1-2. The lines BD and BF are connected to the plus terminals D and F (X1) of the specimens 1-1 and 1-2. Next, the common potential points A and B and the voltage output terminals − and + of the precision power supply 11 are respectively connected. Finally, the detection terminal G (-S) of the precision power supply is connected to the minus terminal C of the specimen 1-1, the detection terminal H (+ S) of the precision power supply is connected to the plus terminal D of the specimen 1-1, Configure 4 terminals. Since the precision power supply 11 detects the supply voltage at the detection terminals G (−S) and H (+ S) terminals, accurate power supply can be supplied by correcting the voltage on the power supply side. Measuring instruments 21 and 22 for measuring output voltages to be measured of the specimens 1-1 and 1-2 are individually connected.

The resistance of the branching electric wire needs to have a resistance value (low resistance) corresponding to the required accuracy. (High resistance is likely to be affected by temperature and the surrounding environment.) For example, a low resistance cable or a shielded cable may be used for wiring that is less susceptible to influence from the peripheral portion. In the embodiment of FIG. 6, two specimens (two sets of branch lines) have been described, but the specimen 1 may be two or more n (two sets of branch lines). In this case, it is necessary to consider such as connecting with a low resistance metal fitting. Although branching may be performed at the terminal block, the number of terminals increases, making it difficult to achieve a constant wiring resistance. Measuring devices 20 (21, 22,...) for measuring output voltages to be measured of n specimens (1-1, 1-2,..., 1-n) are individually connected. ing. Since the measuring instrument 20 has better responsiveness than a precision power supply, a switching device can be provided in some cases. Although the present embodiment has been described in the case of measuring dynamic characteristics, the connection method of the present embodiment can be applied even in the case of measuring static characteristics.
Alternatively, measurement may be performed so that a plurality of systems of a single precision power source and a large number of specimens 1 exist.

  When connecting as described above and measuring the dynamic characteristics of the specimen 1 (1-1, 1-2,..., 1-n), a large number of specimens 1 are used with a single precision power source. (1-1, 1-2,..., 1-n) can be efficiently measured.

  The case where the dynamic characteristics of the specimen 1 are measured by exemplifying the pressure sensor has been described. However, as another embodiment of the present invention, if a sensor using a strain gauge incorporated in a bridge circuit is used, the load, pressure In the case where a mechanical physical quantity such as torque or acceleration is electrically measured. Although the precision power supply 10 has been described with a direct current, the present invention can be applied even in the case of an alternating current.

1 (1-1, 1-2, ..., 1-5) Specimen 10 (11, 12, ..., 15) Precision power supply 20 (21, 22, ..., 25) Measuring instrument 30 Pressure Chamber 31 conduit

Claims (3)

A precision power supply (10) for supplying a constant voltage (E), and a measuring instrument (20) for measuring an output voltage (V) of the specimen (1) including a strain gauge and a bridge circuit, the specimen In contrast to (1), the constant voltage (E) from the precision power supply is supplied to the power supply voltage terminals (X1, X2) of the bridge circuit, and the external voltage applied to the strain gauge is continuously changed while the output voltage of the bridge circuit is changed. In the dynamic characteristic measurement device that measures
The wiring connecting the output terminals (−, +) of the precision power supply (10) and the power supply voltage terminals (X1, X2) of the specimen (1) is branched in the middle, and the wirings have the same resistance. the wire and be Rukoto, one of the precision power supply (10) is, with respect to the supply voltage terminals of the plurality of the specimen (1) (X1, X2), so that it is possible to supply a constant voltage (E) to,
4 terminals further connecting the detection terminals (-S, + S) of the precision power supply (10) to the power supply voltage terminals (X1, X2) of one of the specimens (1) of the plurality of specimens (1) Dynamic characteristic measuring device by the method . The specimen (1) is an intake pressure sensor, and a plurality of the intake pressure sensors are arranged in a pressure chamber (30), and the pressure in the pressure chamber (30) is continuously changed, 2. The dynamic characteristic measuring apparatus according to claim 1 , wherein the output voltage of the bridge circuit of the intake pressure sensor is dynamically measured. The dynamic characteristic measuring device according to claim 1 or 2 , wherein the bridge circuit of the specimen (1) is constituted by a strain gauge of a 4-gauge method.

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