JPH0219712A - Displacement measuring instrument - Google Patents

Abstract

PURPOSE:To remarkably use the title instrument for various purposes by latching a resonance point of an AC signal whose frequency to be supplied is varied, to a primary coil which is brought to inductive coupling to a coil of a no-power source resonance circuit part. CONSTITUTION:First of all, when a displacement quantity is generated in a part to be measured, a resonance frequency of a no-power source resonance circuit part 2 is varied in accordance with its displacement quantity. Also, a resonance point of an AC signal Sa supplied to a primary coil 6 placed in an inductive coupling state is varied. On the other hand, a resonance point detecting part 8 detects this resonance point, and also, based on this timing, a latching part 9 fixes a frequency of a measuring signal generating part 7, that is, a frequency of the AC signal Sa. Therefore, by measuring the frequency in the resonance point in a frequency measuring part 10, and also, calculating the displacement quantity corresponding to the frequency of the resonance point in an arithmetic part 11, the object displacement quantity is obtained. In this regard, in such a case, correlation of the frequency in the resonance point to the displacement quantity is converted to data in advance in the arithmetic part 11.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a displacement measuring device suitable for use in an intracerebral manometer or the like that measures the amount of displacement of a region to be measured in a non-contact manner.

[Background technology and issues]

2. Description of the Related Art As displacement measuring devices for measuring the amount of displacement of an object, various devices typified by differential transformers, potentiometers, etc. have been known.

By the way, when measuring the amount of displacement in a non-contact state, it is necessary to measure the amount of displacement in the non-contact state by optical means, electrostatic means, electromagnetic means, or the like.

However, no matter which method is used, since the amount of displacement is directly measured, there are problems such as the need to position and fix the measurement part with respect to the measurement part, which makes it less convenient to use and makes it difficult to obtain high measurement accuracy. Ta.

Further, with optical means, measurement is impossible due to the presence of a light-shielding medium, and with electrostatic means, measurement becomes difficult when the distance between the media is large, which significantly limits the application.

The object of the present invention is to provide a displacement measuring device 1 that solves the problems existing in the background art.

[Means to solve the problem]

The displacement measuring device 1 according to the present invention first includes a power-free resonant circuit section 2 installed at a site to be measured. The circuit section 2 includes a capacitor 3 and a secondary coil 4, and at least one of capacitance and inductance changes depending on the amount of displacement of the part to be measured.

It also includes a displacement measurement circuit section 5. The circuit section 5 includes a primary coil 6 that can be inductively coupled to the secondary coil 4, a measurement signal generating section 7 that supplies an alternating current signal Sa whose frequency changes to the primary coil 6, and a resonance point P of the alternating current signal Sa. a latch unit 9 that fixes the frequency of the AC signal Sa based on the detection of the resonance point P; a frequency measurement unit IO that measures the frequency of the resonance point P; It is configured to include an arithmetic unit 11 that calculates a corresponding displacement amount.

[For production]

Next, the operation of the displacement measuring device 1 according to the present invention will be explained.

First, when an amount of displacement occurs in the part to be measured, the resonant frequency of the non-power resonant circuit section 2 changes corresponding to the amount of displacement, and furthermore, the AC signal Sa supplied to the primary coil 6 placed in an inductively coupled state The resonance point P of changes.

On the other hand, the resonance point detection section 8 detects the resonance point P, and based on this timing, the latch section 9 fixes the frequency of the measurement signal generation section 7, that is, the frequency of the alternating current signal Sa. Therefore, by measuring the frequency at the resonance point P in the frequency measuring section 10 and further calculating the displacement amount corresponding to the frequency of the resonance point P in the calculation section 11, the target displacement amount can be obtained. Note that in this case, the correlation between the frequency at the resonance point and the amount of displacement is previously converted into data in the calculation unit 11.

〔Example〕

Next, preferred embodiments of the present invention will be described in detail based on the drawings.

First, the configuration of a displacement measuring device 1 according to the present invention will be explained with reference to FIGS. 1 and 2.

The displacement measuring device 1 consists of a non-power-supply resonance circuit section 2 and a displacement measuring circuit section 5, which are constructed separately.

The unpowered resonant circuit section 2 is configured by connecting a capacitor 3 and a secondary coil 4 in a loop. Further, the capacitor 3 is configured such that its capacitance changes in accordance with the amount of displacement of the portion to be measured. In this case, for example, the dielectric position and the electrode plate position may be configured to be relatively displaceable following the amount of displacement of the part to be measured. Note that instead of changing the capacitance of the capacitor 3, the inductance of the secondary coil 4 may be changed. In this case, for example, the position of the core used in the secondary coil 4 may be configured to be able to be displaced in accordance with the amount of displacement of the part to be measured.

On the other hand, the displacement measurement circuit section 5 includes a primary coil 6 that can be inductively coupled to the secondary coil 4 in a non-contact manner. Further, a measurement signal generator 7 is connected to the primary coil 6, which supplies an alternating current signal Sa whose frequency is swept. The measurement signal generator 7 includes an oscillator 20 that generates clock pulses, a counter 21 that alternately counts the clock pulses in up and down directions and outputs the counted value as a digital signal, and a D converter that converts this digital signal into an analog signal. /A converter 22 and a sweep frequency generator 23 that outputs an alternating current signal Sa whose frequency changes in accordance with the amplitude of the analog signal, and this alternating current signal Sa is supplied to the primary coil 6.

Further, a resonance point detection section 8 is connected to the primary coil 6 to detect a resonance point P of the alternating current signal Sa. An example of the resonance point detection section 8 is shown in FIG. The detection unit 8 includes a detection circuit 25 that detects the AC signal Sa supplied to the primary coil 6;
a filter 26 for removing high frequency signals from the output signal of 5;
A peak hold circuit 27 that holds the peak value of the output signal (inverted signal) of the filter 26, an amplifier 28 that obtains the deviation value between the beam value and the actual measurement value, and a comparison between the deviation value and the reference value,
It is equipped with a comparator 29 whose output state is reversed when the deviation value exceeds the reference value. Furthermore, a latch unit 9 is connected between the counter 2I and the D/A converter 22 to fix the count value of the counter 21 at the same time as the reversal of the output state in the resonance point detection unit 8, that is, the detection timing of the resonance point P. .

2. Also connected to the primary coil 6 is a frequency measuring section 10 that measures the frequency of the alternating current signal Sa supplied thereto. In addition, a calculation unit 11 that calculates the amount of displacement based on the resonance point p (J:, frequency) is connected to the measurement unit 1O. Data or data tables, etc. are set in advance, and a microcomputer function is provided.In addition, on the output side of the calculation unit 11, there is a D/A converter 31 for converting the calculated displacement amount into an analog signal; Vessel 31
An output section 32 such as a predetermined control system or display device that supplies an output signal is connected.

Next, regarding the functions of the displacement measuring device l according to the present invention,
This will be explained with reference to FIGS. 1 and 3.

First, the oscillator 20 generates a clock pulse, and the same signal is supplied to the counter 21 . The counter 21 counts these clock pulses and outputs them as a 12-bit digital signal. In addition, the counter 21 has a function of counting in the positive direction from the set state, counting in the negative direction by counting up, and counting in the positive direction again depending on the state. Up-down is repeated alternately.Therefore, if the digital signal of the counter 21 is converted into an analog signal via the D/A converter 22, a triangular wave signal Se shown in FIG. 3(a) is obtained.

Further, the triangular wave signal Sc is supplied to a sweep frequency generator 23, which outputs an AC signal Sa shown in FIG. 3(b) whose frequency changes in proportion to the amplitude value of the triangular wave signal SC. Note that the frequency range of the second AC signal Sa is, for example, 33
Select 0kHz to 360kHz. The alternating current signal Sa is then supplied to the primary coil 6. At this time, the amplitude of the AC signal Sa output from the sweep frequency generator 23 is constant, but by connecting the primary coil 6, the resonance point [> is changed as shown in the figure (', b). The waveform becomes a dip.

On the other hand, the resonance point P (maximum dip point) of the AC signal Sa is detected by the resonance point detection section 8. Upon detection of the resonance point P, the output state of the detection section 8 is reversed15. Second tie °;
(Thus, the latch unit 9 fixes the count value of the counter 21. As a result, the alternating current signal Sa of the fixed constant frequency L-port resonance frequency is maintained to be supplied to the primary film 6.

Therefore, if the frequency measuring unit IO measures the frequency of the AC signal Sa supplied to the primary coil [i, the resonance point P
frequency can be obtained. In addition, the frequency measurement is
For example, the calculation may be made by counting the clock of the calculation unit II in a predetermined cycle period of the AC signal Sa. Then, the calculation unit 11 calculates the corresponding displacement amount C from the frequency of the resonance point P. The second displacement amount is supplied to the output section 32 and can be displayed on a display or the like.

Since the frequency of the resonance point P is directly measured in this manner, it is not affected by drift on the measurement signal generating section 7 side, and an accurate displacement amount can be obtained.

Next, a usage example will be explained with reference to FIG. 4.

The displacement measuring device 1 according to the present invention is suitable for use in an intracerebral pressure sensor 50 as shown in FIG. 1. The intracerebral pressure sensor section 51 has a built-in unpowered resonant circuit section 2 consisting of a secondary coil 4a and a nihon sensor 3a, and a primary coil 6 and a probe 57 are embedded in the intracerebral pressure sensor section 51.
In addition, the displacement measurement circuit section 5 is built into the measurement device main body 53 to constitute a displacement measurement device 1. Intracerebral pressure sensor section 51
Intracerebral pressure is applied to the internal space of the brain via the catheter 54, and the amount of pressure corresponding to the magnitude of this intracerebral pressure is 1. The movable core 55 is supported by a bellows 56 so as to be displaced. and,
The movable core 55 is inserted into the hollow portion of the coil 4a to change the inductance of the coil 4a. Therefore, the movable core 55 is displaced in response to changes in intracerebral pressure,
This amount of displacement can be measured by a displacement measuring device 1.

Although the embodiments have been described in detail above, the present invention is not limited to these embodiments.

For example, it can be applied to the amount of displacement of any object measured in a non-contact state. Furthermore, any circuit configuration that performs the same function can be adopted. Other details may be changed as desired without departing from the gist of the present invention.

〔Effect of the invention〕

As described above, the displacement measuring device l according to the present invention is equipped with a primary coil inductively coupled to the coil of the unpowered resonant circuit section, and an AC signal whose frequency changes is supplied to the primary coil. Since the resonance point is latched and the displacement amount is calculated by directly measuring the frequency of the resonance point based on this, the following effects are obtained.

■ Since there is no need to position the measuring part relative to the measuring part, it is easy to use and can be used in a wide range of applications.

■ Measurement accuracy is not affected by positioning, etc., and the displacement is an indirect physical quantity using frequency as a medium, making highly accurate measurement possible.

■ Since the frequency at the resonance point is latched and the frequency is directly measured, it is not affected by circuit drift, etc.
Reliable and accurate measurements are possible.

[Brief explanation of the drawing]

First opening: Block circuit diagram of the displacement measuring device according to the present invention, Figure 2: Specific circuit diagram of the resonance point detection section in the displacement measuring device, Figure 3: Time chart of signals in the main parts of the displacement measuring device. , Figure 4: A configuration diagram of an intracerebral manometer showing an example of the use of the displacement measuring device. In the drawing, l: displacement measurement device 2: powerless resonance circuit section 3: capacitor 4: secondary coil 5: displacement measurement circuit section 7: measurement signal generation section 9: latch section 11: calculation section P: resonance point 6: Primary coil 8: Resonance point detection section IO two-station frequency measurement section a: AC signal Fig. 1 Patent applicant Nagano Keiki Seisakusho Co., Ltd. Patent attorney 2 1) Shigeru 2 Fig. 3 Fig. 50'

Claims (1)

[Scope of Claims] [1] A displacement measuring device comprising the following circuit sections. (a) an unpowered resonant circuit section that includes a capacitor and a secondary coil, and in which at least one of capacitance and inductance changes in response to the amount of displacement of the part to be measured; (b) a primary coil that can be inductively coupled to the secondary coil; and,
a measurement signal generation section that supplies an alternating current signal whose frequency changes to the primary coil; a resonance point detection section that detects a resonance point of the alternating current signal; and a latch section that fixes the frequency of the alternating current signal based on the detection of the resonance point. and a displacement measurement circuit section comprising a frequency measurement section that measures the frequency of the resonance point, and a calculation section that calculates the amount of displacement corresponding to the frequency of the resonance point; [2] The measurement signal generation section counts the clock signal. 2. The displacement measuring device according to claim 1, further comprising a counter, and changing the frequency of the alternating current signal in accordance with the count value of the counter. [3] The displacement measuring device according to claim 1, wherein the power-free resonance circuit section is built into an intracerebral pressure sensor section buried within the human body.