JPS60262067A - Method of measuring capacity - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for measuring capacitance, particularly minute capacitance, in which the frequency of an oscillator is determined by the capacitance connected to the input terminal of a circuit. , which uses an oscillator whose output □frequency is a coefficient of capacity.
Further, in the above method, a reference (calibration) capacitance is used which is alternately connected to the measurement oscillator using a switch device llll1+ together with the capacitance to be measured. □(Prior art) As a prior art example of the present invention, Finnish patent No. 5466
No. 4 and No. 57319 (same as U.S. Pat. Nos. 4,295,090 and 4,295,019). These patents relate to methods of measuring minute capacitances, involving electronically switched switches, and are particularly described for use in telemetric geosondes.

Capacitive sensors, i.e. sensors whose capacitance depends on the parameter (variable) to be measured, are used in radiosondes to measure parameters such as pressure, temperature, humidity, etc. The capacitance of these sensors is usually very small, ranging from a few picofloods to 20°30.40 at most 100°
There's a flood.

Measuring minute capacitances has problems such as stray capacitance, input voltage fluctuations, warpage, and other disturbances. Also, these Sen+
J-it has individuality within a certain range, for example, its nonlinearity and temperature characteristics are individual.

Conventionally, when measuring temperature, temperature, pressure, or the like using electrical or electromechanical sensors, one or more precisely known reference values (references) are used. or a reference device is provided within the measurement electronics or mechanism to increase the accuracy of the measurement circuit or/and sensor.

In the conventional example, a reference capacitance is used in conjunction with a capacitance sensor, and this reference capacitance is used alternately with the measuring force φ in a measuring circuit consisting of usually 80 oscillators whose frequency is determined by the connected capacitance. or, alternatively, the output of the measuring circuit is set to the correct level by means of a reference capacitance. In particular, it uses a calibration measurement circuit with one reference value connected in a bridge; with this method the measurement is accurate only when the electrical value of the reference is close to the sensor value, e.g. is in a state of balance.

If the difference between the sensor value and MJIIl is large, a large value error will occur. For example, the error is determined by the degree of enhancement of the electrical measuring circuit.

(Problems to be Solved by Development I) The advantage of wiring a single standard is the simplification of the measurement circuit in any case. The basis of such prior art will be explained below with reference to FIG.

The advantage of the measurement method with two M standards or multiple standards is the measurement accuracy over a wide measurement range, and the disadvantage is the complexity of the configuration and calculations. The basics of such conventional fittings will be explained above with reference to FIGS.

(Means and Means for Solving the Problems) The purpose of the present invention is to improve the layer for measuring minute capacitances of 0 to 100 PF, thereby improving the circuit and measurement method. It is very precise.

1] The object of the present invention is that the conventional measurement method and measurement circuit using two calibrators are required to obtain the result. This eliminates the need for complicated calculation operations.

It is an object of the present invention that such a measurement method, i.e. a ``self-correcting'' measuring circuit, does not change the reference to which it refers for the output variable, but that is This is to deal with the creep that occurs in the measurement circuit.

The main structure of the invention to solve the above problems is a method using two external auxiliary calibrators.1. The external auxiliary calibration signal thus obtained is compared with the output signal of the measuring circuit, which is obtained as a reference on the basis of a reflex capacitor. The signal size <[That is, the output signal, etc., produced by comparing it with an external auxiliary calibrator is used as a feedback signal that controls the circuit. The measuring circuit is controlled by the feedback signal so as to result in the differential signal or its equivalent being approximately zero or a preset value. Therefore, the output signal, which is the measured value of the capacitance by the measuring circuit constructed by the method described above, is accurately adjusted.

The object of the present invention is achieved by attaching an external auxiliary calibrator to the measurement circuit that obtains the output signal due to the unique characteristics of the calibration reference capacitor, which auxiliary calibrator is free from interference from various sources. It is stabilized and independent of the measurement circuit and its creep, just as we are.

The variables, i.e. the output variables obtained from the characteristics of the calibration capacitance and those obtained by comparison with the auxiliary calibrator, i.e. the ones based on the calibration, form a differential signal and are determined in the measuring circuit as one effect. Another effect is to tilt the measuring circuit over a number of repeated measuring cycles. As a result, the difference between the calibration volume and the external calibrator becomes zero or approaches zero. The comparison is preferably carried out in a fixed position, and a differential signal is obtained between the first external calibrator and the first reference capacitor, which acts to give a constant value to the measuring circuit. If it changes, it is the effect of giving off-cell l- of the measuring circuit.

A second external auxiliary reference i [container and second reference,
11! The differential signal obtained by the pacitares determines the slope of the measuring circuit, for example the degree of enhancement. If the measuring method of the measuring circuit is by changing the frequency, one differential signal is applied to the one giving the fundamental frequency, and the other differential signal is applied, for example by converting the frequency to a change in capacitance. Use for dynamic things.

(Example) The present invention will be described in detail below by using a schematic representation of the background of the present invention or a more specific diagram, with reference to the drawings.

FIG. 1 illustrates a measurement method using one reference at XY coordinate 1. For example, the value at the center of the measurement range X1 of a capacitor is determined by the point X1.
A straight line K is fixed as Y and passes through that point due to the operation of the measuring circuit. is marked on the vessel.

The component in the X direction is then an input variable, for example the swing width of the capacitor being measured, and Y is an output variable, for example in this case the DC voltage or the frequency over which it changes. In any case, creeping of the measuring circuit or other factors may cause the fundamental characteristics of the system to vary from the straight line drawn by K to the line drawn as an example by the dotted line and by the dotted line to 2. They will leave like this.

Thereby, the measurement range around the point of Xo within the allowed error range is effectively narrow.

What is shown in FIG. 2 shows a measurement method using two references, and is the origin of the present invention. In this method, two references, reference 1 and reference 2, are acted upon, which are the X-Y elements of two points on the straight line Ko, which is the basic operating line of the system, i.e. , Yl and x2, Y2 are fixed.

In practice, due to changes in wetness or other factors, the characteristic curve of the system changes within the range shown by the curve f and `` on both sides of the straight line K . The fixed range X can be made wider than the above-mentioned X. As a result, the measurement range x 2 can be made wider by at least one order of magnitude compared to the measurement method using one reference.

Having clarified the possibilities, a more detailed description of the invention follows. This is accomplished in conventional techniques by connecting two references to the measurement circuit.
The method and circuit of the present invention are excellent because they do not require complicated calculation operations, and the measurement method and circuit of the present invention are extremely simplified and concrete. , will be explained with reference to FIG.

In Fig. 3, the system is measured with the capacity 1, (
C) Two reference tolerances a'10 and 11 as 12
Consists of (CR1 and CH2). For that reference,
The values of the ¥11 vacitas 10 and 11 are matched with the points indicated as x1 and x2 in FIG. 2, and the measurement range x2 is extended to the middle of and outside of these two points. .

The measuring circuit includes an electronic changeover switch 13, which is controlled by a circuit 15, which is controlled by a clock 14.

Control signals a1, rl, r2 of the control circuits 15J and 15' cause the electronic changeover switch 13 to select the capacitance C to be measured.
The reference passacitors cR1 and CR2 are alternately connected to the measurement circuit 16.

In this method, it is clear that the measuring circuit 16 includes, for example, an RC oscillator and thus measures a capacitance of 0 to 100 p[, and that reference capacitors are alternately connected to the input circuit to determine the frequency of said oscillator. is determined, and the measuring circuit 16 uses a distributor (f<stributor) and other known switching techniques so that the output variable obtained from the measuring circuit is, for example, a DC voltage or a frequency, which is The capacitance is substantially linear with the electrical value of ICH.

If the output variable of the measurement circuit 16 is temporarily determined to be a voltage tJ 1 , this voltage U 1 passes through the first comparison circuit 19 and further reaches the second comparison circuit 20 .

According to the invention, the measuring circuit and method uses C12 external auxiliary reference circuits 17 and 18 from which, for example, direct voltages UR1 and UR2 are obtained, Those are the respective comparison circuits 1
It will lead to 9.20.

The auxiliary reference voltages uR1 and Ul(
2 and the output voltage u1 from the measurement circuit are compared to the comparison circuits 19 and 20.
The input voltage is .

The comparison circuits 19 and 20 are the changeover switch 13 of the control circuit 15.
The output voltages U and U from the result comparison circuits 19 and 20 in A are controlled by the pulse sequence obtained for the purpose of
is obtained, and by this signal, the measuring circuit 16 is controlled by +<, C via c circuits 21 and 22 (O-pass filter).

The present invention provides a first control message 1) (). , 1 is the stationary term of the measuring circuit 1G.If we consider the operation of the measuring circuit 1G as the stationary term, then the operation of the 2nd control [1st signal]C
2 of the measuring circuit e.g. increase rll [by coefficient (slope)
This is achieved by doing this.

Control signals Uo, and (). 2 acts on the measurement circuit to reduce the voltage () and C2 in stages. This feedback effect is repeated, for example, by the control circuit 15 controlling the changeover switch, and is repeated over many measurement cycles. In the meantime, the differential voltages U and C2 stepwise reach almost zero. .

When the differential voltages U and C2 are substantially close to the zero point, the measurement circuit 16 is accurately regulated.Thereby, the changeover switch 13 is controlled by the control circuit 15, and the The changeover switch 13 connects the capacitance 12 to be measured to the measuring circuit. At the same time, the control circuit 15 of the changeover switch 13 controls the A-Lewingermen 1 to 28 or other suitable devices, and the output signal ( ), are connected, and as a result, a calibrated output signal U.ol is produced. ゛ (What is shown in Fig. 4 is a specific wiring diagram, and this is a microcapacitance (0 to 100 DF)
This constitutes a measurement circuit.

The measured frequency is approximately 100 Hz, and the frequency of
5 and 26 (gate 1°, etc.) to a sufficiently low frequency that can accommodate the ZY rectangle, and the conversion adds 4f to the measurement result.

Special notes on the structure and operation of the multi'F+1 tube circuit 27 are available.

A comparison of time X is made by gates 31 and 32.

Gates 33 and 34 force the 47 .mu.F capacitor 01's voltage B to a calibrated current by reference CR1 and CR2. Output signal U. 0 is a frequency modulation (burst) in FIG. 4, the frequency of which depends on the measured electrical width information of the capacitive detector C0.

The outputs are connected in the same way as was done with references CR1 and CR2, so that the pulse provides information on the electrical value of the detector over its width (between one cycle and one cycle).

The wiring diagram in Figure 4 shows that the number of pulses should be calculated from a frequency burst or one with slight changes (this is an essential part of the wiring system, especially for capacitive This circuit is patented as a circuit for measuring a detector. (same as January).

The variables have been tested by JP-A. The auxiliary □reference time component is obtained from the crystal oscillator 24 and further from pin 3 of the distributor Micro 1 No. Kit 25 (402/1). Zeroing is done immediately after (combining pins 3 and 6) a second auxiliary reference is not required, nothing
If so, it can be obtained with the Microrekit 26 (4040), which is a distributor with different distribution numbers. By this method, seven reflexes CR1 and CR2 can be created. The burst is obtained from its number of pulses, which consists of subtracting one of the values of the references CR1, CR2.

Claims (10)

[Claims] (1) A method of measuring capacitance, especially regarding minute capacitances, using an electronic measurement method that uses a measurement oscillator whose output frequency is determined by the coefficient of the capacitance connected to the input terminal of the circuit. It uses two reference capacitors (C1CH2), and its electrical values (Xl, X2) are within the measurement range (×
2) is set and connected inside the capacitance (CH
) are interchanged with multiple capacitors, and the measuring oscillator is connected to two external auxiliary references (R1, R
2) and the resulting auxiliary signal (UR
l, UR2) and the reference volume 1fi (CR1,
CR2) compares the output signal (Ul) obtained by the measuring circuit, which signal (U , U
, 1) R2), and the control of times a1 and 6 is performed based on this difference. Feedback signal (().1, LJ,,2)
becomes. The circuit 16 is controlled by the feedback signal to make the differential signal (Ul, U2) or its net value Q or a set specified value, and the determination (judgment) based on the output signal' is based on the capacitance (C ), measurement circuit 1
A capacitance measuring method characterized by measuring 6 in an accurately adjusted state. (2) # differential signal @ (LJl, LJ2) is formed during many measurement cycles, the differential signal (Ul, sometimes measured capacitance 11 (C)), output variable (Ul, U) The measuring method according to claim 1, characterized in that: 0T is obtained. (3) What is called the specified value or offset of the measuring circuit is achieved using the control signal (UCl) generated by the comparator 19 based on one of the differential signals (Ul), for example, Depending on the degree of increase in circuit 16, the coefficient (slope) of measurement circuit 1-6 is determined by the differential signal from the other one.
(U2) and the control signal (U'.2) obtained by the comparator 20, the six pressure adjustments are made in the course of a number of measurement cycles by the capacitance reference (U'.2).
CR1, CR2) and external reference (R,, -R>
3. The measuring method according to claim 2, wherein: is equal to 0 or is a predetermined constant. (4) 1.Contents to be determined @ (CH) Jin, 2. q reference capacitors (CR1, CR2) are for measurement, circuit 1
The control circuit 1 for the changeover switch 13 is switched by an electronic changeover switch 13 connected to the changeover switch 13, which changeover switch 13 is controlled by a changeover switch control circuit 15 controlled by a clock 14.
The control signals (rl, r2) by 5 are the reference capacitor a
(CR1, CR2), one (rl) controls a comparator 19 and the other (r2) controls another converter 20
4. A measuring method according to any one of claims 1 to 3, characterized in that: (5) Using a device with a fundamental measurement frequency of approximately 100 Hz, reduce the fundamental frequency to a low level such as a gate delay using a distributor 25, 26, etc., and prevent it from interfering with the measurement results. The measuring method according to any one of claims 1 to 4, characterized in that the effect is excluded. (6) The measuring method according to any one of claims 1 to 5, wherein the output signal (Uool, ) is a DC voltage. (7) Depending on the method applied to the circuit, the output signal is a frequency burst and each frequency is measured. Container 1 of Rubegi detector (Measurement method according to any one of claims 1 to 5, characterized in that it is based on information on the amplitude of CI4>.) (8) The measuring method according to claim 7, characterized in that the number of pulses in a frequency burst is calculated, and the result of the calculation is used to measure the volume 1 (CH) to be measured. . (9) The number of pulses formed by the value of the - side reference is subtracted from the number of pulses of the frequency burst, and the calculation result obtained thereby is used to determine the measured reverberation capacitance. The measuring method according to claim 8 of the Patent FF Claim. (10) A measuring method in which the measuring method according to claim 1(o) is used in a radiosonde for measuring atmospheric pressure, hot stone, and/or humidity.