JPS6312262B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a capacitive element loss measuring device.

Conventionally, an apparatus for measuring loss of a capacitive element has been proposed with the configuration described below with reference to FIG.

That is, e ₀ = E ₀ sinωt ...(1) (where E ₀ is the amplitude, ω is the angular frequency,
t is time) It has an AC constant voltage source 1 that can obtain an AC constant voltage _e0 , and current-voltage conversion is performed through a capacitive element 2 to be measured represented by a parallel equivalent circuit of a capacitance C _P and a conductance g. Based on the AC current that is connected to the input side of the circuit 3 and is supplied from the output side of the current-voltage conversion circuit 3 from the AC constant voltage source 1 side through the capacitive element 2 to be measured, e ₁ = -E ₀ R _S (ωC _P cosωt + gsinωt) ...(2) The electrostatic capacitance of the capacitive element 2 to be measured, C _P
The AC voltage e ₁ is the sum (vector sum) of the AC voltage proportional to the conductance g and the AC voltage proportional to the conductance g. In this case, the current-voltage conversion circuit 3 has an input terminal a connected to the AC constant voltage source 1 through the capacitive element 2 to be measured, an input terminal b connected to the ground and having the opposite polarity to the input terminal a, It consists of an operational amplifier 4 having an output terminal c having a polarity opposite to that of an input terminal a, and a resistor R _S connected between the output terminal c and the input terminal a.

Also, the input side of the phase shift circuit 5 is connected to the AC constant voltage source 1, and from the output side of the phase shift circuit 5, based on the AC constant voltage e ₀ , e ₃ = -E ₀ /R ₁ ωC ₁ sin (ωt−π/2)=E ₀ /R ₁ ωC ₁ cos
The arrangement is such that an AC voltage e 3 having a phase difference of 90° with respect to an AC constant voltage e ₀ expressed as ωt ( ₃ ) is obtained. In this case, the phase shift circuit 5 includes an operational amplifier 6 having an input terminal a, an input terminal b connected to ground and having a polarity opposite to that of the input terminal a, and an output terminal c having a polarity opposite to the input terminal a. , a resistor R ₁ having one end connected to the input terminal a of the operational amplifier 6 and the other end connected to the AC constant voltage source 1, and a capacitor C ₁ connected between the output terminal c and the input terminal a of the operational amplifier 6. Become.

The alternating current voltage _e1 obtained from the current-voltage conversion circuit 3 is supplied to one input terminal of the multiplier circuit 8 through an amplifier 7 with polarity reversal as required.
On the other hand, the AC voltage _e3 obtained from the phase shift circuit 5 is supplied to the other input terminal of the multiplier circuit 8 through an amplifier 9 as required, and the AC voltage e3 is supplied from the multiplier circuit 8 as required.
Based on e ₁ and e ₃ , E ₁ = K ₁ K ₃ E ₀ ² R _S C _P /2R ₁ C ₁ ...(4) The capacitance C _P of the capacitive element 2 to be measured is expressed as
A DC voltage E ₁ proportional to the voltage E 1 can be obtained. In this case, the multiplier circuit 8 is e ₄ =K ₁ e ₁・K ₃ e ₃ =K ₁ E ₀ R _S (ωC _P cosωt+gsinωt)・K ₃ E ₀ /R ₁ ωC ₁ cos
ωt =K ₁ K ₃ E ₀ ² R _S C _P (1 + cos2ωt) / 2R ₁ C ₁ +K ₁ K ₃ E ₀ ² R _S gs
in2ωt／2R ₁ ωC ₁ =K ₁ K ₃ E ₀ ² R _S C _P ／2R ₁ C ₁ +K ₁ K ₃ E ₀ ² R _S (ωC _P cos2ωt＋gs
in2ωt)/2R ₁ ωC ₁ ...(5) (however, K ₁ and K ₃ are constants), AC voltage
Multiplier circuit main body 10 configured to obtain output e ₄ of the product of the voltage based on e ₁ and the voltage based on AC voltage e ₃
and a low frequency converter 11 configured to obtain a DC voltage E ₁ expressed by equation (4) based on the output e ₄ connected to its output side.

Also, the AC voltage obtained from the current-voltage conversion circuit 3
e ₁ is supplied to one input terminal of another multiplier circuit 12 through the amplifier 7 with polarity inversion described above as necessary, and an AC constant voltage from the AC constant voltage source 1 is supplied to the other input terminal of the multiplier circuit 12. e ₀ is supplied through the amplifier 13 as necessary, and based on the AC voltages e ₀ and e ₁ from the multiplier circuit 12, E ₂ = K ₀ K ₁ E ₀ ² R _S g/2 ...(6) A DC voltage E ₂ proportional to the conductance g of the capacitive element 2 to be measured is obtained. In this case, the multiplier circuit 12 is e ₅ =K ₀ e ₀・K ₁ e ₁ =K ₀ E ₀ sinωt・K ₁ E ₀ R _S (ωC _P cosωt+gsinωt) =K ₀ K ₁ E ₀ ² R _S ωC _P sin2ωt/ 2+K ₀ K ₁ E ₀ ² R _S g(1-cos
2ωt)/2 =K ₀ K ₁ E ₀ ² R _S g/2+K ₀ K ₁ E ₀ ² R _S (ωC _P sin2ωt−gsin2
ωt)/2...(7) (where K ₀ and K ₁ are constants), AC voltage
Multiplier circuit main body 14 configured to obtain output e ₅ which is the product of the output based on e ₀ and the output based on AC voltage e ₁
and a low frequency converter 15 connected to its output side and configured to obtain a DC voltage E ₂ expressed by equation (6) based on the output e ₅ .

Furthermore, the DC voltage obtained from multiplier circuits 8 and 12
E ₁ and E ₂ are supplied to the division circuit 24 of the arithmetic circuit 23, and from this, based on the DC voltages E ₁ and E ₂ , E ₂ /E ₁ =K ₀ K ₁ E ₀ ² R _S g/2・2R ₁ C ₁ ／K ₁ K ₃ E ₀ ² R _S C _P ＝K ₀ R ₁ C ₁ ／K ₃・g／C _P ＝g／ω ₀ C _P ＝tan〓＝D……(8
) The output Q representing the loss D of the capacitive element 2 to be measured is obtained.

The above is a conventionally proposed loss measuring device for a capacitive element. It is possible to determine the loss D expressed as g/ω ₀ C _P =D, but since the output Q is the output obtained by dividing the DC voltages E ₁ and E ₂ , the DC voltage The AC voltages multiplied by the AC voltages e ₃ and e ₀ for the multiplier circuits 8 and 12 obtained by E ₁ and E ₂ , respectively, are at a level corresponding to the values of the capacitance C _P and conductance g of the capacitive element 2 to be measured. AC voltage that takes
Since e ₁ , the DC voltage E ₁ from multiplier circuits 8 and 12
and E ₂ are difficult to obtain with high resolution regardless of the values of the capacitance C _P and conductance g of the capacitive element 2 to be measured. It has the disadvantage that high resolution cannot be obtained regardless of the values of capacitance C _P and conductance g.

Therefore, the present invention aims to propose a novel capacitive element loss measuring device free from such drawbacks, which will become clear from the detailed description below.

FIG. 2 shows an example of a loss measuring device for a capacitive element according to the present invention. Corresponding parts to those in FIG. AC constant voltage source 1 that provides an AC constant voltage e ₀
has a capacitance C _P and a conductance g
capacitive element 2 to be measured represented by a parallel equivalent circuit with
Through the current-voltage conversion circuit 3 consisting of an operational amplifier 4 and a resistor R _S as described above in FIG.
The input side of the current-voltage conversion circuit 3 is connected, and from the output side of the current-voltage conversion circuit 3, the capacitive element 2 to be measured is
An AC voltage e ₁ is obtained which is the sum of an AC voltage proportional to the capacitance _CP and an AC voltage proportional to the conductance g.

Also, the input side of a phase shift circuit 5 consisting of an operational amplifier 6, a resistor R ₁ and a capacitor C ₁ is connected to the AC constant voltage source 1 as described above in FIG. From the output side, an AC voltage e ₃ having a phase difference of 90° with respect to the AC constant voltage e ₀ expressed by equation (3) described above is obtained in the same way as shown in FIG. 1. .

Therefore, the AC voltage e ₁ from the current-voltage conversion circuit 3
is supplied to an amplifier circuit 31, which is configured to obtain an output voltage having a substantially constant level even when the level of the input voltage changes, through an amplifier 7 with polarity reversal as necessary;
Therefore, based on the AC voltage e ₁ , an AC voltage e ₂ having an approximately constant level is obtained, which is expressed as e ₂ = K ₂ E ₀ R _S (ωC _P cosωt + gsinωt) (9) (where K ₂ is a coefficient). It is being done as it should be done. In this case, the AC voltage e ₂ has an approximately constant level, which means that This means that the absolute value of the AC voltage e ₂ expressed by |e ₂ | has _a substantially constant level.
(9) Even if the capacitance C _P and conductance g of the capacitive element 2 to be measured change within the expected range, (9)
Even if C _P and g in the equation change within the expected range, the coefficient K ₂ (amplification degree) changes accordingly, so that the AC voltage e ₂ can be obtained at a substantially constant level. It consists of an amplifier circuit with AGC function.

Furthermore, the AC voltage e ₂ having a substantially constant level obtained from the amplifier circuit 31 mentioned above is applied to one side of the multiplication circuit 8 consisting of the multiplication circuit main body 10 and the low frequency amplifier 11 similar to those mentioned above in FIG. The AC voltage e ₃ expressed by the equation (3) mentioned above, which is supplied to the input side of one multiplier circuit 8 and obtained from the phase shift circuit 5 to the other input side of the multiplier circuit 8, is required as described above in FIG. is supplied through the amplifier 9 accordingly, and thus the multiplier circuit 8
Therefore, based on the AC voltages e ₂ and e ₃ , E ₁ ′=K ₂ K ₃ E ₀ ² R _S C _P /2R ₁ C ₁ ……(4 )', the capacitance C _P of the capacitive element 2 to be measured, expressed as
It is designed so that a DC voltage E ₁ ' proportional to can be obtained. In this case, from the multiplier circuit main body 10 of the multiplier circuit 8, e ₄ ′=e ₂・K ₃ e ₃ =K ₂ E ₀ R _S (ωC _P cosωt+gsinωt)・K ₃ E ₀ /R ₁ ωC ₁ cos
ωt =K ₂ K ₃ E ₀ ² R _S C _P (1 + cos2ωt) / 2R ₁ C ₁ +K ₂ K ₃ E ₀ ² R _S gs
in2ωt／2R ₁ ωC ₁ =K ₂ K ₃ E ₀ ² R _S C _P ／2R ₁ C ₁ +K ₂ K ₃ E ₀ ² R _S (ωC _P cos2ωt＋gs
in2ωt)/2R ₁ ωC ₁ ……(5)′ The alternating current voltage e ₄ ′ is obtained,
Correspondingly, the DC voltage E ₁ ' expressed by the above-mentioned equation (4)' is obtained from the low frequency converter 11.

Furthermore, the AC voltage e ₂ having a substantially constant level obtained from the amplifier circuit 31 is applied to one input side of the multiplier circuit 12 consisting of the multiplier circuit main body 14 and the low-frequency amplifier 15 similar to those described above in FIG. The AC constant voltage expressed by the above-mentioned equation (1) obtained from the AC constant voltage source 1 is supplied to the other input side of the multiplier circuit 12.
e ₀ is supplied via the amplifier 13 as required, as described above in FIG.
Therefore, E ₂ ′=K ₀ K ₂ E 0 ² R _S g _/ 2R ₁ C ₁ ……(6) based on the AC voltages e ₂ and e ₀ and according to equation (6) shown above in FIG. A DC voltage E ₂ ', which is proportional to the conductance g of the capacitive element 2 to be measured, is obtained. In this case, from the multiplier circuit body 14 of the multiplier circuit 12, e ₅ '=K ₀ e ₀・e ₂ =K ₀ E ₀ sinωt・K ₂ E ₀ R _S according to equation (7) described above in FIG. (ωC _P cosωt＋gsinωt) =K ₀ K ₂ E ₀ ² R _S ωC _P sin2ωt／2+K ₀ K ₂ E ₀ ² R _S g(1−cos
2ωt)/2 =K ₀ K ₂ E ₀ ² R _S g/2+K ₀ K ₂ E ₀ ² R _S (ωC _P sin2ωt−gcos2
ωt)/2...(7)' The alternating current voltage e ₅ ' is obtained.
Correspondingly, the DC voltage E ₂ ' expressed by the above-mentioned equation (6)' is obtained from the low frequency converter 15.

Also, the DC voltage obtained from multiplier circuits 8 and 12
E ₁ ′ and E ₂ ′ are connected to the arithmetic circuit 23 as in the case of FIG.
is supplied to the division circuit 24, from which the DC voltage
Based on E ₁ ′ and E ₂ ′, E ₂ ′ / E ₁ ′ = K ₀ K ₂ E ₀ ² R _S g/2・2R ₁ C ₁ /K ₂ K ₃ E ₀ ² R _S C _P = K ₀ R ₁ C ₁ ／K ₃・g／C _P ＝g／ω _{0 CP} ＝tan〓＝D……(8
)', the capacitive element 2 to be measured in the case of Fig. 1
The output Q' representing the loss D of the capacitive element 2 to be measured is the same as the output Q representing the loss D of the capacitive element 2 to be measured.

The above is an example of the configuration of the capacitive element loss measuring device according to the present invention. According to this configuration, the output Q' obtained from the division circuit 24 of the arithmetic circuit 23 by dividing the DC voltages E ₁ ' and E ₂ ' is the same as the output Q in the case of Fig. 1, so the output Q' can be expressed as g/ω ₀ C _P = D as seen in the parallel equivalent circuit of the capacitive element 2 under test, as in the case of Fig. 1. It is clear that it is possible to determine the loss D that occurs.

However, in the case of the capacitive element loss measuring device according to the present invention as shown in FIG.
These are the outputs obtained by dividing E _{1 '} and E ₂ ', and are then multiplied by the AC voltages e ₃ and e ₀ to the resulting multiplier circuits 8 and 12, _respectively . The AC voltage is the capacitance of the capacitive element 2 to be measured.
Since the AC voltage e ₂ is at a substantially constant level regardless of the values of C _P and conductance g, the DC voltages E ₁ ' and E ₂ ' are applied to the capacitance of the capacitive element 2 to be measured from the multiplier circuits 8 and 12, respectively. In order to obtain high resolution regardless of the values of C _P and conductance g, the AC voltage multiplied by the AC voltages e ₃ and e ₀ for the multiplier circuits 8 and 12, respectively, is This is easier than the conventional case described above in _{FIG .}
Regardless of the values of the capacitance C _P and conductance g of the capacitive element 2 to be measured, it is easy to obtain Q' with a higher resolution than the output Q in the conventional case described above in Fig. 1. It is something that is.

Therefore, in the case of the capacitive element loss measuring device according to the present invention described above in FIG _. Regardless of the value of the conductance g, the present invention has the great feature that it can provide higher resolution than the conventional case described above with reference to FIG.

The above description has only shown one example of the present invention, and for example, an amplifier circuit may be inserted between each of the multiplier circuits 8 and 12 and the removal circuit 24 as necessary, and It is also possible to replace the circuits 8 and 12 with a synchronous detection circuit in which the multiplier circuit bodies 10 and 14 are replaced with the synchronous detection circuit body, and various other modifications and changes may be made without departing from the spirit of the present invention. will be able to do it.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing a conventional capacitive element loss measuring device, and FIG. 2 is a system diagram showing an example of a capacitive element loss measuring device according to the present invention. In the figure, 1 is an AC constant voltage source, 2 is a capacitive element to be measured,
C _P is capacitance, g is conductance, 3 is a current-voltage conversion circuit, 5 is a phase shift circuit, 8 and 12 are multiplication circuits, 10 and 14 are multiplication circuit bodies, 11 and 15 are low frequency amplifiers, 31 indicate amplifier circuits, respectively.

Claims (1)

[Scope of Claims] 1. An AC constant voltage source connected to the AC constant voltage source through a capacitance element to be measured, and based on an AC current supplied from the AC constant voltage source side through the capacitance element to be measured. a current-voltage conversion circuit configured to obtain a first alternating voltage that is the sum of an alternating current voltage proportional to the capacitance of the measuring capacitive element and an alternating current voltage proportional to the conductance; An amplifier circuit with an AGC function configured to obtain a second AC voltage having a substantially constant level even when the level changes, and a phase difference of 90° with respect to the AC constant voltage obtained from the AC constant voltage source. a phase shift circuit configured to obtain a third alternating current voltage having the above-mentioned second and third alternating current voltages; a second DC voltage proportional to the conductance of the capacitive element to be measured, based on the AC voltage obtained from the AC constant voltage source and the second AC voltage; a second multiplier circuit or a synchronous detection circuit designed to obtain
A loss measuring device for a capacitive element, comprising: an arithmetic circuit configured to obtain an output representing loss of the capacitive element to be measured, which is obtained by dividing a DC voltage of 1 by a first DC voltage.