CN112666400B - Capacitance measuring circuit capable of automatically compensating parasitic capacitance, and use method and application thereof - Google Patents
Capacitance measuring circuit capable of automatically compensating parasitic capacitance, and use method and application thereof Download PDFInfo
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Abstract
The invention discloses aA capacitance measurement circuit capable of automatically compensating for parasitic capacitance, a method of use and application thereof, the circuit comprising: programmable capacitor C T One end of (2) is connected with a reference capacitor C 0 Is connected with one end of the connecting rod; programmable capacitor C T And the other end of the meter amplifier is connected with the positive input end V of the meter amplifier I+ Or inverting input V I‑ Is connected with reference capacitor C 0 And the other end of the meter amplifier is connected with the reverse input end V of the meter amplifier I‑ Or positive input terminal V I+ Is connected with each other; the output end of the instrument amplifier is connected with the input end of the analog-digital conversion chip through the conditioning circuit; the output end of the analog-digital conversion chip is connected with the input end of the singlechip system; the output end of the singlechip system is connected with the display; the output end of the singlechip system is connected with a programmable capacitor C through a proportional-differential integral controller T Is connected with each other. The circuit of the invention can automatically compensate the influence of the parasitic capacitance in the capacitive sensor on the measuring circuit, and can accurately measure the change of the tiny capacitance.
Description
Technical Field
The invention belongs to the fields of electrical engineering, instrument science and technology, and particularly relates to a capacitance measuring circuit capable of automatically compensating parasitic capacitance, and a use method and application thereof.
Background
With the development of the electronic industry, the capacitive sensor is more widely applied, such as a temperature and humidity sensor, a pressure sensor, and the like. These sensors use the principle of capacitors to convert the change of other physical quantities into the change of capacitance; the change in the physical quantity to be detected can be reversely deduced by detecting the change in the capacitance of the sensor. Thus, the accuracy of the capacitance measurement circuit directly affects the measurement accuracy and sensitivity of the sensor.
When the design of the capacitive sensor is finished, the capacitive sensor has an inherent capacitance which is called parasitic capacitance, and compared with the inherent parasitic capacitance, the capacitance change caused by the change of external physical quantity is much smaller; also due to the parasitic capacitance itself, the amount of change in capacitance tends to be submerged in the noise of the measurement system and undetected. The ac method is a common method of measuring minute capacitance at present, but it is difficult to solve the influence of parasitic capacitance on measurement.
In summary, there is a need for an ac-based capacitance measurement circuit that automatically compensates for parasitic capacitance to solve this problem.
Disclosure of Invention
The invention aims to provide a capacitance measuring circuit capable of automatically compensating parasitic capacitance, and a use method and application thereof, so as to solve the technical problem that the parasitic capacitance of a sensor cannot be automatically compensated by the existing method. The circuit of the invention can automatically compensate the influence of the parasitic capacitance in the capacitive sensor on the measuring circuit, and can accurately measure the change of the tiny capacitance.
In order to achieve the above purpose, the invention adopts the following technical scheme:
the invention relates to a capacitance measuring circuit capable of automatically compensating parasitic capacitance, which comprises: programmable capacitor C T Reference capacitance C 0 The system comprises an instrument amplifier, a conditioning circuit, an analog-digital conversion chip, a singlechip system, a proportional-differential integral controller and a display;
programmable capacitor C T One end of (2) is connected with a reference capacitor C 0 Is connected with one end of the circuit board and is used for inputting an excitation signal; programmable capacitor C T And the other end of the meter amplifier is connected with the positive input end V of the meter amplifier I+ Or inverting input V I- Is connected with reference capacitor C 0 And the other end of the meter amplifier is connected with the reverse input end V of the meter amplifier I- Or positive input terminal V I+ Is connected with each other; wherein the programmable capacitor C T For parallel connection of the capacitance C to be measured x ；
The output end of the instrument amplifier is connected with the input end of the analog-digital conversion chip through the conditioning circuit; the conditioning circuit is used for converting the received capacitance signal into a direct-current voltage signal and outputting the direct-current voltage signal; the analog-digital conversion chip is used for converting the received direct-current voltage signal into a digital signal and outputting the digital signal;
the output end of the analog-digital conversion chip is connected with the input end of the singlechip system; the output end of the singlechip system is connected with the display; the output end of the singlechip system is connected with a programmable capacitor C through a proportional-differential integral controller T Is connected with each other; the singlechip system is used for calculating and outputting the capacitance value of the tested capacitor according to the received digital signal.
A further improvement of the present invention is that it further comprises: and the signal generating chip is used for sending out an alternating current signal serving as an excitation signal.
A further improvement of the present invention is that it further comprises: a first amplifier for increasing the excitation signal.
A further improvement of the present invention is that the conditioning circuit comprises:
a phase shifter for shifting the input excitation signal by a fixed angle such that the instrumentation amplifier output is 0 ° or 180 ° out of phase with the phase shifter output; wherein the excitation signal is a sinusoidal signal;
the multiplier is used for taking the output of the instrument amplifier and the output of the phase shifter as input signals and performing multiplication operation to output an obtained result;
the first filter is used for filtering alternating current components in the output result of the multiplier and remaining direct current components as output signals;
the second amplifier is used for amplifying the output signal of the first filter to obtain an amplified signal;
and the second filter is used for filtering the signal amplified by the second amplifier to obtain a direct-current voltage signal.
A further development of the invention is that the initial excitation signal S 1 Sine wave a×sin (wt+0), then:
V I+ ＝S 1 *jw*R 1 (C T +C x )/(1+jw*R 1 (C T +C x ))；
V I- ＝S 1 *jw*R 4 *C 0 /(1+jw*R 4 *C 0 )；
wherein V is I+ V being the voltage at the non-inverting input of the instrumentation amplifier I- The voltage value of the inverting input end of the instrument amplifier is represented by j, wherein j is an imaginary number, w is an angular velocity, and the relation between w and the frequency f is w=2pi f, R 4 ＝R 1 Providing a return path loop for the filter resistor to input bias current, C T For programmable capacitance, C x C is the capacitance value of the sensor to be measured 0 Is the reference capacitance.
A further development of the invention is that V I+ ＝S 1 *jw*R 4 (C T +C x )；
V I- ＝S 1 *jw*R 4 *C 0 。
A further development of the invention is that the output S of the instrumentation amplifier 2 The method comprises the following steps:
S 2 ＝K G *(V I+ -V I- )
＝K G *jw*R 4 *(C T +C x -C 0 )*S 1 ；
wherein K is G K is the amplification factor of the instrument amplifier 1 ＝w*R 4 。
A further development of the invention is that the initial excitation signal S 1 Obtaining the output S of the phase shifter through the phase shifter 3 Expressed as:
S 3 ＝-jw*R 5 *C 1 *S 1 ；
wherein R is 5 Differential resistance, C, of the phase shifter 1 Differential capacitance, K, of the phase shifter 2 ＝w*R 5 *C 1 ；
The gain of the conditioning circuit is K 3 The output of the conditioning circuit is V o ：
V o ＝K G *K 1 *K 2 *K 3 (C T +C x -C 0 )；
Wherein K is G 、K 1 、K 2 、K 3 、C T 、C 0 Are known amounts;
the calculation in the singlechip system comprises the following steps: cx=v o /(K G *K 1 *K 2 *K 3 )+C 0 -C T ；
Wherein C is x ＝C p +ΔC；C p The parasitic capacitance and DeltaC are variable capacitance components.
The invention relates to a using method of a capacitance measuring circuit, which comprises the following steps:
before the sensor to be tested is connected, the capacity of the programmable capacitor is changed according to the output voltageValue C T Order C T ＝C 0 ；
Zero correction is carried out, V o ＝K*(C T -C 0 ) =0; wherein k=k G *K 1 *K 2 *K 3 ；
Accessing the sensor to be tested, V o ＝K*(C p +C T -C 0 )＝K*C p ；
Compensating for parasitic capacitance, comprising: according to the output voltage V o The capacitance value of the programmable capacitor is changed to make C p +C T -C 0 =0, and the capacitance of the programmable capacitor at this time is recorded as C T1 ，C p ＝C 0 -C T1 The method comprises the steps of carrying out a first treatment on the surface of the At this time, the measuring circuit outputs V o ＝K*(C p +C T1 -C 0 ) =0, the output voltage of the measurement circuit: v (V) o ＝K*(C p +△C+C T1 -C 0 )
＝K*△C；
The operation of compensating the parasitic capacitance of the capacitive sensor is completed.
The application of the capacitance measuring circuit is used for a capacitance sensor or a capacitance actuator.
Compared with the prior art, the invention has the following beneficial effects:
the circuit of the invention can automatically compensate the influence of the parasitic capacitance in the capacitive sensor on the measuring circuit, and can accurately measure the change of the tiny capacitance. Specifically, the invention is realized by connecting a programmable capacitor C T And the capacitance C to be measured x The parallel connection is used as the in-phase input end of the instrument amplifier, the analog-digital conversion chip is used for converting the output voltage of the measuring circuit into digital quantity and transmitting the digital quantity to the singlechip, the singlechip can change the capacitance value of the programmable capacitor through the PID control algorithm according to the obtained voltage value and the operation instruction, and the influence of the parasitic capacitance in the capacitive sensor on the measuring circuit is eliminated through the closed loop, so that the tiny capacitance is accurately measured.
In addition, the parasitic capacitance of a common capacitive sensor is often several tens of pF, and the capacitance change amount caused by the measurement is at the fF level (1 pf=1000 fF); the traditional measuring circuit directly conditions and amplifies the capacitance of the sensor, but the variation of the capacitance of the sensor is too small relative to the parasitic capacitance, so that the sensor is submerged in the noise of the measuring circuit. The micro capacitance measuring circuit capable of automatically compensating the parasitic capacitance can form a closed loop with the singlechip through the measuring circuit, change the programmable capacitance to balance the bridge to eliminate the influence of the parasitic capacitance on the subsequent measuring circuit, and only condition and amplify the variation of the capacitance of the sensor.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following description of the embodiments or the drawings used in the description of the prior art will make a brief description; it will be apparent to those of ordinary skill in the art that the drawings in the following description are of some embodiments of the invention and that other drawings may be derived from them without undue effort.
FIG. 1 is a schematic block diagram of a wiring for a capacitance measurement circuit for a capacitive sensor that automatically compensates for parasitic capacitance in accordance with an embodiment of the present invention;
FIG. 2 is a schematic circuit diagram of a capacitance measurement circuit for a capacitive sensor that automatically compensates for parasitic capacitance according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of an LCD display interface according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a LABVIEW-based upper computer program interface in an embodiment of the present invention;
FIG. 5 is a diagram showing the relationship between the measured capacitance and the output voltage according to the embodiment of the present invention.
Detailed Description
In order to make the purposes, technical effects and technical solutions of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention are clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention; it will be apparent that the described embodiments are some of the embodiments of the present invention. Other embodiments, which may be made by those of ordinary skill in the art based on the disclosed embodiments without undue burden, are within the scope of the present invention.
Referring to fig. 1, a capacitance measuring circuit for a capacitive sensor capable of automatically compensating parasitic capacitance according to an embodiment of the invention includes: SCM system (STM 32), analog-to-digital conversion chip (ADC), instrumentation amplifier, phase shifter, multiplier, low pass filter, programmable Capacitor (CT), LCD display screen, and reference capacitor (C) 0 )。
Referring to fig. 2, a capacitance measuring circuit for a capacitive sensor capable of automatically compensating parasitic capacitance according to an embodiment of the invention includes:
the excitation source is an alternating current signal AC emitted by a signal generating chip (such as AD 9833), one end of the excitation source is grounded, and the other end of the excitation source is connected with the input end of the amplifier 1 and the input end of the phase shifter, wherein the amplifier 1 and the phase shifter are common circuits.
The output end of the amplifier is connected with the programmable capacitor C T Capacitance C to be measured x And reference capacitance C 0 。
Capacitance C to be measured x And programmable capacitor C T The other end is connected with the positive end V of the instrument amplifier I+ (or the opposite end V I- ) Reference capacitance C 0 The other end is connected with the reverse end V of the instrument amplifier I- (or the forward end V I+ )。
X with output end connected with multiplier of instrument amplifier 1 Port, output end of phase shifter is connected with Y of multiplier 1 A port.
The output end of the multiplier is connected with a common filter and an amplifier, and finally outputs a direct current voltage which is in linear relation with the measured capacitor. The ADC chip (such as AD 7606) acquires the output voltage and then converts the output voltage into a digital signal to be transmitted to the singlechip system (such as STM 32), and then the singlechip system can change the capacitance value of the programmable capacitor through a PID algorithm according to the operation instruction of the man-machine interaction interface on the LCD or the man-machine interaction interface on the upper computer. The invention realizes automatic adjustment of the capacitance value of the programmable capacitor through the circuit shown in fig. 2 to zero the measuring circuit and compensate the parasitic capacitance of the measured sensor, thereby realizing the measurement of the tiny capacitor.
An embodiment of the invention is used for capacitive transmissionThe working principle of a capacitance measuring circuit of the sensor capable of automatically compensating parasitic capacitance is as follows: the invention generates a sine wave A by using a signal generating chip AD9833 (wt+0) to be marked as S 1 . Then S is carried out 1 Applied to C via an amplifier T 、C x 、C 0 V is obtained by I+ And V is equal to I- Then:
V I+ ＝S 1 *jw*R 1 (C T +C x )/(1+jw*R 1 (C T +C x ))；
V I- ＝S 1 *jw*R 4 *C 0 /(1+jw*R 4 *C 0 )；
the invention selects proper frequency w and resistance value R 4 And capacitance C and jw R 4 (C T +C x )≈10 -4 、jw*R 4 C 0 ≈10 -4 The method comprises the steps of carrying out a first treatment on the surface of the Then 1+jw R 4 (C T +C x )≈1、1+jw*R 4 C 0 Approximately 1 (e.g. w is 5kHZ, R 4 ＝R 1 Taking 100deg.OMEGA, the programmable capacitance used in this embodiment is NCD2400M capacitance variation range 12.5 pF-194 pF, in order to ensure that the bridge can reach equilibrium state C 0 The range of the value is 12.5 pF-194 pF, and C is taken in consideration of the fact that the design can compensate parasitic capacitance to the greatest extent 0 =194 pF) the above can be reduced to:
V I+ ＝S 1 *jw*R 1 (C T +C x )；
V I- ＝S 1 *jw*R 4 *C 0 ；
wherein V is I+ V being the voltage at the non-inverting input of the instrumentation amplifier I- The voltage value of the inverting input end of the instrument amplifier is represented by j, wherein j is an imaginary number, w is an angular velocity, and the relation between w and the frequency f is w=2pi f, R 4 ＝R 1 Providing a return path loop for the filter resistor to input bias current, C T For programmable capacitance, C x C is the capacitance value of the sensor to be measured 0 Is the reference capacitance.
The two sine wave signals are processed by subtracter composed of instrument amplifierWill obtain an amplitude and C T +C x -C 0 Proportional sine wave S 2 Recording the amplification factor of the instrument amplifier as K G Then:
S 2 ＝K G *(V I+ -V I- )
＝K G *jw*R 4 *(C T +C x -C 0 )*S 1 ；
k is recorded 1 ＝w*R 4 。
The formula is as follows: s is S 2 Is the amplitude and (C) T +C x -C 0 ) A proportional ac signal.
Another way S 1 Obtaining S through a common phase shifter 3 Then:
S 3 ＝-jw*R 5 *S 1 ；
k is recorded 2 ＝w*R 5 。
S 2 And S is equal to 3 After subsequent multiplier, filter combinations, a sum (C) is obtained T +C x -C 0 ) Direct current signal in direct proportion, the gain of the conditioning circuit is recorded as K 3 Then:
V o ＝K G *K 1 *K 2 *K 3 (C T +C x -C 0 )；
wherein K in the above formula G 、K 1 、K 2 、K 3 、C T 、C 0 Are known amounts.
The analog-digital conversion chip collects the voltage V o The digital signals are converted into digital signals and transmitted to a singlechip system, and then the method can be used for obtaining:
Cx＝V o /(K G *K 1 *K 2 *K 3 )+C 0 -C T ；
wherein C is x Is formed by parasitic capacitance C of a capacitive sensor p And a variable capacitance deltac, namely: c (C) x ＝C p +ΔC。
The conditioning circuit of the embodiment of the invention comprises:
phase shifter forIn the excitation signal S to be input 1 Phase shifting by a fixed angle the instrumentation amplifier output S 2 And the phase shifter output S 3 Is 0 ° or 180 ° out of phase; wherein the excitation signal is a sinusoidal signal;
the multiplier is used for taking the output of the instrument amplifier and the output of the phase shifter as input signals and performing multiplication operation; due to S 2 And S is equal to 3 Is a sinusoidal signal with the same frequency and 0 or 180 degrees phase difference, so S 2 And S is equal to 3 The result of the multiplication is a direct current component plus a sinusoidal signal of 2 times the frequency.
The first filter filters the alternating current component in the output of the multiplier, leaving only the direct current component.
And a second amplifier for amplifying the signal output from the filter.
And the second filter is used for filtering the output of the amplifier again to obtain a smoother direct-current voltage signal.
The conventional ac-method capacitance measuring circuit cannot automatically eliminate the influence of parasitic capacitance in the sensor on the measuring circuit, and the parasitic capacitance C of the sensor itself is different from the capacitive sensor p Is different, which makes it difficult for them to detect the capacitance value of the minute capacitance deltac. And balancing the bridge according to the output of the measuring circuit and the programmable capacitance adjustment to eliminate the influence of parasitic capacitance on the measuring circuit. The measuring circuit provided by the invention can adjust the programmable capacitance through the closed loop formed by the measuring circuit and the singlechip, and the bridge formed by the instrument amplifier in the measuring circuit is in a balanced state through the closed loop adjusting the programmable capacitance after the measured capacitance is connected, so that the influence of the parasitic capacitance of the capacitive sensor on the measuring circuit is eliminated.
The application method of the capacitance measuring circuit comprises the following steps:
before the sensor to be tested is connected, the capacitance C of the programmable capacitor is changed according to the output voltage T Order C T ＝C 0 。
Zeroing the measurement circuit, then:
V o ＝K*(C T -C 0 )＝0；
wherein k=k G *K 1 *K 2 *K 3 。
Then the sensor to be tested is connected, and the capacitance sensor has parasitic capacitance C p At this time
V o ＝K*(C p +C T -C 0 )
＝K*C p ；
We then begin compensating for parasitic capacitance by clicking on an operating interface on the LCD, such as fig. 3, or an interface on a host computer, such as the "Parasitic Capacitance" button on fig. 4. When the singlechip detects that the button Parasitic Capacitance is clicked, the output voltage V is obtained o To change the capacitance of the programmable capacitor, and finally let C p +C T -C 0 =0, and the capacitance of the programmable capacitor at this time is recorded as C T1 C is then p ＝C 0 -C T1 . At this time, the measuring circuit outputs V o ＝K*(C p +C T1 -C 0 ) =0, so that the output voltage of the circuit is measured later:
V o ＝K*(C p +△C+C T1 -C 0 )
＝K*△C；
by the above formula, it can be found that the output voltage is directly proportional to the capacitance change amount deltac of the capacitive sensor and is independent of the parasitic capacitance of the capacitive sensor, so that the influence of the parasitic capacitance on the output voltage is eliminated.
The operation of compensating the parasitic capacitance of the capacitive sensor is completed through the steps.
In summary, the invention is implemented by integrating a programmable capacitor C T And the capacitance C to be measured x The parallel connection is used as the in-phase input end of the instrument amplifier, the analog-digital conversion chip is used for converting the output voltage of the measuring circuit into digital quantity and transmitting the digital quantity to the singlechip, the singlechip can change the capacitance value of the programmable capacitor through the PID control algorithm according to the obtained voltage value and the operation instruction, and the influence of the parasitic capacitance in the capacitive sensor on the measuring circuit is eliminated through the closed loop, so that the tiny capacitance is accurately measured. The parasitic capacitance of a typical capacitive sensor is mostly tens of pF, while the capacitance variation caused by the measurement is at the fF level (1 pf=1000 fF); the traditional alternating current method measurement circuit can directly condition and amplify the capacitance of the sensor, but the change of the capacitance of the sensor is too small relative to the parasitic capacitance, so that the sensor is submerged in the noise of the measurement circuit. The micro capacitance measuring circuit capable of automatically compensating the parasitic capacitance can form a closed loop with the singlechip through the measuring circuit, and change the programmable capacitance to balance the bridge to eliminate the influence of the parasitic capacitance on the subsequent measuring circuit, so that the change of the capacitance of the sensor is only conditioned and amplified.
Experimental data of the embodiment of the invention:
referring to fig. 5, the measurement circuit is first calibrated using standard ceramic capacitors; after the calibration is completed, the capacitive two-dimensional scanning micro mirror C1130 developed by the known micro sensor is measured, and the measurement results are shown in table 1:
TABLE 1 example measurement results
As can be seen from Table 1, the parasitic capacitance of the capacitive two-dimensional scanning micro mirror C1130 is 32.79pF, and the measuring circuit provided by the invention can well compensate the parasitic capacitance, thereby achieving the purpose of the invention.
The above embodiments are only for illustrating the technical solution of the present invention and not for limiting the same, and although the present invention has been described in detail with reference to the above embodiments, one skilled in the art may make modifications and equivalents to the specific embodiments of the present invention, and any modifications and equivalents not departing from the spirit and scope of the present invention are within the scope of the claims of the present invention.
Claims (10)
1. A capacitance measurement circuit capable of automatically compensating for parasitic capacitance, comprising: programmable capacitor C T Reference capacitance C 0 Meter amplifier, conditioning circuit, analog to digitalThe system comprises a conversion chip, a singlechip system, a proportional-differential integral controller and a display;
programmable capacitor C T One end of (2) is connected with a reference capacitor C 0 Is connected with one end of the circuit board and is used for inputting an excitation signal; programmable capacitor C T And the other end of the meter amplifier is connected with the positive input end V of the meter amplifier I+ Or inverting input V I- Is connected with reference capacitor C 0 And the other end of the meter amplifier is connected with the reverse input end V of the meter amplifier I- Or positive input terminal V I+ Is connected with each other; wherein the programmable capacitor C T For parallel connection of the capacitance C to be measured x ；
The output end of the instrument amplifier is connected with the input end of the analog-digital conversion chip through the conditioning circuit; the conditioning circuit is used for converting the received capacitance signal into a direct-current voltage signal and outputting the direct-current voltage signal; the analog-digital conversion chip is used for converting the received direct-current voltage signal into a digital signal and outputting the digital signal;
the output end of the analog-digital conversion chip is connected with the input end of the singlechip system; the output end of the singlechip system is connected with the display; the output end of the singlechip system is connected with a programmable capacitor C through a proportional-differential integral controller T Is connected with each other; the singlechip system is used for calculating and outputting the capacitance value of the tested capacitor according to the received digital signal.
2. The capacitance measuring circuit capable of automatically compensating for parasitic capacitance of claim 1, further comprising: and the signal generating chip is used for sending out an alternating current signal serving as an excitation signal.
3. The capacitance measuring circuit capable of automatically compensating for parasitic capacitance of claim 2, further comprising: a first amplifier for increasing the excitation signal.
4. The capacitance measuring circuit capable of automatically compensating for parasitic capacitance of claim 1, wherein said conditioning circuit comprises:
a phase shifter for shifting the input excitation signal by a fixed angle such that the instrumentation amplifier output is 0 ° or 180 ° out of phase with the phase shifter output; wherein the excitation signal is a sinusoidal signal;
the multiplier is used for taking the output of the instrument amplifier and the output of the phase shifter as input signals and performing multiplication operation to output an obtained result;
the first filter is used for filtering alternating current components in the output result of the multiplier and remaining direct current components as output signals;
the second amplifier is used for amplifying the output signal of the first filter to obtain an amplified signal;
and the second filter is used for filtering the signal amplified by the second amplifier to obtain a direct-current voltage signal.
5. The capacitance measuring circuit capable of automatically compensating for parasitic capacitance as in claim 4, wherein the initial excitation signal S 1 Sine wave a×sin (wt+0), then:
V I+ ＝S 1 *jw*R 1 (C T +C x )/(1+jw*R 1 (C T +C x ))；
V I- ＝S 1 *jw*R 4 *C 0 /(1+jw*R 4 *C 0 )；
wherein V is I+ V being the voltage at the non-inverting input of the instrumentation amplifier I- The voltage value of the inverting input end of the instrument amplifier is represented by j, wherein j is an imaginary number, w is an angular velocity, and the relation between w and the frequency f is w=2pi f, R 4 ＝R 1 Providing a return path loop for the filter resistor to input bias current, C T For programmable capacitance, C x C is the capacitance value of the sensor to be measured 0 Is the reference capacitance.
6. A capacitance measuring circuit capable of automatically compensating for parasitic capacitance according to claim 5,
V I+ ＝S 1 *jw*R 4 (C T +C x )；
V I- ＝S 1 *jw*R 4 *C 0 。
7. the capacitance measuring circuit capable of automatically compensating for parasitic capacitance as in claim 5, wherein the output S of the instrumentation amplifier 2 The method comprises the following steps:
S 2 ＝K G *(V I+ -V I- )
＝K G *jw*R 4 *(C T +C x -C 0 )*S 1 ；
wherein K is G K is the amplification factor of the instrument amplifier 1 ＝w*R 4 。
8. The capacitance measuring circuit capable of automatically compensating for parasitic capacitance as in claim 7, wherein the initial excitation signal S 1 Obtaining the output S of the phase shifter through the phase shifter 3 Expressed as:
S 3 ＝-jw*R 5 *C 1 *S 1 ；
wherein R is 5 Differential resistance, C, of the phase shifter 1 Differential capacitance, K, of the phase shifter 2 ＝w*R 5 *C 1 ；
The gain of the conditioning circuit is K 3 The output of the conditioning circuit is V o ：
V o ＝K G *K 1 *K 2 *K 3 (C T +C x -C 0 )；
Wherein K is G 、K 1 、K 2 、K 3 、C T 、C 0 Are known amounts;
the calculation in the singlechip system comprises the following steps: cx=v o /(K G *K 1 *K 2 *K 3 )+C 0 -C T ；
Wherein C is x ＝C p +ΔC；C p The parasitic capacitance and DeltaC are variable capacitance components.
9. A method of using the capacitance measuring circuit of claim 1, comprising the steps of:
before the sensor to be tested is connected, the capacitance C of the programmable capacitor is changed according to the output voltage T Order C T ＝C 0 ；
Zero correction is carried out, V o ＝K*(C T -C 0 ) =0; wherein k=k G *K 1 *K 2 *K 3 ；
Accessing the sensor to be tested, V o ＝K*(C p +C T -C 0 )＝K*C p ；
Compensating for parasitic capacitance, comprising: according to the output voltage V o The capacitance value of the programmable capacitor is changed to make C p +C T -C 0 =0, and the capacitance of the programmable capacitor at this time is recorded as C T1 ，C p ＝C 0 -C T1 The method comprises the steps of carrying out a first treatment on the surface of the At this time, the measuring circuit outputs V o ＝K*(C p +C T1 -C 0 ) =0, the output voltage of the measurement circuit:
V o ＝K*(C p +△C+C T1 -C 0 )
＝K*△C；
the operation of compensating the parasitic capacitance of the capacitive sensor is completed.
10. Use of a capacitance measuring circuit according to claim 1 for a capacitive sensor or a capacitive actuator.
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| CN114113801B (en) * | 2022-01-24 | 2022-06-21 | 上海艾为微电子技术有限公司 | Capacitance detection method and capacitance detection device |
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002350477A (en) * | 2001-05-29 | 2002-12-04 | Sumitomo Metal Ind Ltd | Impedance detecting circuit |
| CN204832352U (en) * | 2015-05-21 | 2015-12-02 | 成都理工大学 | Little measurement of capacitance appearance of phase -delay total mark |
| CN108333437A (en) * | 2018-02-09 | 2018-07-27 | 深圳华清精密科技有限公司 | Micro capacitance system and measurement method |
| CN111693784A (en) * | 2020-07-06 | 2020-09-22 | 北京先通康桥医药科技有限公司 | Weak capacitance change measuring circuit |
-
2020
- 2020-11-18 CN CN202011297661.7A patent/CN112666400B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002350477A (en) * | 2001-05-29 | 2002-12-04 | Sumitomo Metal Ind Ltd | Impedance detecting circuit |
| CN204832352U (en) * | 2015-05-21 | 2015-12-02 | 成都理工大学 | Little measurement of capacitance appearance of phase -delay total mark |
| CN108333437A (en) * | 2018-02-09 | 2018-07-27 | 深圳华清精密科技有限公司 | Micro capacitance system and measurement method |
| CN111693784A (en) * | 2020-07-06 | 2020-09-22 | 北京先通康桥医药科技有限公司 | Weak capacitance change measuring circuit |
Non-Patent Citations (1)
| Title |
|---|
| 一种新型电容式位移传感器电路设计;王晓立;唐德尧;朱石砂;;计算机测量与控制(第07期);全文 * |
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