JPS62176119A - Triple-terminal standard capacitor - 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 (Field of Industrial Application) The present invention relates to a three-terminal standard capacitor used for precision measurement of various quantities of electricity, and in particular, the present invention relates to a three-terminal standard capacitor used for precision measurement of various quantities of electricity, and in particular, to This invention relates to a three-terminal standard capacitor with a circuit added to compensate for the loss factor.

[Conventional technology]

Among the two-terminal air capacitors for standard devices that are specially designed for the structure, there are high-precision ones with a loss coefficient of 10-5 or less, but because such air capacitors have a small dielectric constant, Used only at low volumes. Therefore, dielectric capacitors (-6 using a dielectric material other than air) that are made in a small size and have a loss coefficient of about 10-4 to 10-3 are currently widely used as standard capacitors.

However, as mentioned above, dielectric capacitors cannot be said to have an extremely small loss coefficient, so when measuring each level of electric power using this as a standard, the more complex the measurement circuit, the more the loss coefficient of the capacitor. becomes a problem as an error factor.

In order to eliminate measurement errors due to such loss coefficients, conventionally used electronic capacitor measuring instruments use operational amplifiers to reverse the polarity of the voltage drop at the resistor terminal and convert it into a negative equivalent. A method of obtaining resistance is used.

[Problem to be solved by the invention]

In such conventional compensation methods, operational amplifier noise,
Due to constraints due to the characteristics of the amplifier itself, such as gain and stability, compensation for the 10 lapse coefficient of a dielectric capacitor is limited to about 10 -4. However, in order to provide a standard capacitor suitable for high precision measurements, it is necessary to compensate its loss factor to 10-5 or less.

[Structure and operation of the invention]

Therefore, the present invention provides a Y-connected compensation circuit consisting of a three-terminal standard capacitor in which a first capacitor is housed in a shield case that also serves as a ground terminal, second and third capacitors υ, and a resistor. A three-terminal standard capacitor with a self-destruction coefficient close to zero is realized by connecting a negative equivalent resistance obtained from this compensation circuit between both terminals of the first capacitor.

〔Example〕

The present invention will be explained in detail below.

FIG. 1 shows an embodiment of a three-terminal type 1% j-contact sensor according to the present invention.

In the same figure, the capacitor J3 is a dielectric capacitor used as the defined capacitance of this standard Q+ capacitor. In terms of mounting, this dielectric capacitor 1SCo is
As shown in FIG. 2(a), it is housed in an electrostatic shield case S which also serves as a ground terminal G. These can be expressed as an equivalent circuit as shown in FIG. 2(b), and this equivalent circuit element is also used in FIG. Incidentally, the configuration shown in FIG. 2 is that of a conventional general three-terminal standard capacitor.

Furthermore, in this embodiment, small capacitance capacitors C and C are connected in series between both terminals H and L of the dielectric capacitor -co, and the interconnection point of the two-handed capacitance capacitors C1 and C2 and the shield case S (ground terminal A variable resistor R is connected between G) and G). As will be described later, the loss coefficient of the dielectric capacitor C8 can be compensated by the Y-connected circuit consisting of the two small capacitance capacitors C1°C2 and the variable resistor R. Note that this compensation circuit is provided outside the shield case S.

Hereinafter, the operation of this embodiment configured as described above will be explained.

First, the loss coefficient of a conventional standard capacitor before adding a compensation circuit will be explained with reference to FIG. 2(b).

In the figure, the capacitor CC is the ground capacitance of this standard capacitor due to the deflection between the dielectric g1° g2 body capacitor C8 and the shield case S. In addition, a resistance Ro parallel to the dielectric capacitor C6 is an equivalent loss resistance corresponding to the dielectric loss of this dielectric capacitor "co". In the following explanation, the reference numeral of each circuit element is the electrical resistance of each element. Also used as a target value.

One terminal H of the dielectric capacitor C8 is connected to the power supply, and the other terminal is used at the same ground potential as the shield case S. Therefore, the ground capacitance Cg1 is added in parallel to the power supply, and the ground capacitance Ca2 substantially no longer functions as a capacitor. As a result, the ground capacitance CC of this standard capacitor is separated from the measurement object, and the dielectric capacitor C8 <Il'
1) will be used as this standard capacitor 4) defined capacitance.

Therefore, the equivalent loss coefficient of this conventional standard capacitor at the angular frequency ω is: is expressed as Do=1/ωCoR8.

Next, the operation of the compensation circuit including the small capacitance capacitors C and C2 and the variable resistor R will be explained.

FIG. 3(a) shows only this compensation circuit.

Converting this to an equivalent circuit with a △ connection as shown in the same figure (b), we find that both terminals of the dielectric capacitor C6) -1, 11
? ! The parallel impedance ZH1 added to I is expressed as ω1 ωU2. Here, if we select the circuit constants so that , we get , and the parallel impedance Z! 1. is equivalent to a negative resistance component.

Next, based on the above consideration, the operation of this embodiment will be explained with reference to FIG. 4, which is a rewrite of FIG. 1 using the equivalent circuit of FIG. 3(b).

In Fig. 4, a new impedance ZIIcI' is generated in the compensation circuit between terminals H, L and ground terminal G.
Since ZLG is an impedance to ground, it is a circuit constant that does not give any disadvantage g1 and g2 to the defined capacitance C8, similar to the ground capacitance CC of a conventional three-terminal standard capacitor.Therefore, the parallel impedance Only Z acts on the defined capacitance C8. As mentioned above, the parallel impedance Z11 is a negative resistance component, and its value is determined by the angular frequency ω and the circuit constants C, C2, and R of the compensation circuit. Therefore, by adjusting the variable resistor R appropriately, l ZHLI =R.

If we make it so, the definition volume ff1c. It is clear that the loss factor associated with can be compensated to zero. To explain in more detail, the loss coefficient D11. related to the defined capacitance C in this embodiment. is ω of<o
G.

It is expressed as Note that the first term of equation (3) is is the loss coefficient of the dielectric capacitor C6 itself, and the second term is the loss coefficient. There is a term C that compensates for.

Based on this equation (3), the variable resistor R is changed to Sl according to the angular frequency ω so that
! By adjusting I, the loss coefficient DIIL can be compensated to zero.

As described above, according to this embodiment, the loss coefficient is 10-4.
By simply connecting a very simple circuit consisting of two fixed capacitors and a variable resistor to a three-terminal JfA quasi-capacitor of approximately 10-3, the loss coefficient of this standard capacitor can be adjusted for a specific frequency. It is possible to supplement by 10. Since this amount of compensation can be adjusted using a variable resistor, component capacitors with a tolerance of several percent are sufficient for the compensation circuit capacitors C and C2. Furthermore, since no electronic circuits such as oil cylinder amplifiers are used, the loss coefficient can be compensated to a value extremely close to zero, making it possible to use standard capacitors for high-precision measurements that require a loss coefficient of 10-5 or less. can be provided to In addition, you can freely respond to changes in frequency by adjusting the variable resistor R for small changes, and by changing the selection of capacitors C1 and C2 and variable resistor R for large changes. I can do it.

(Effects of the Invention) As explained above, according to the present invention, by adding a negative parallel equivalent resistance obtained from two capacitors and a resistor to a three-terminal standard capacitor, this standard capacitor can be Since the loss resistance is compensated for (τt), the compensation t!1m can be easily adjusted by adjusting the circuit constants of the compensation circuit. However, since no electronic circuit such as a differential amplifier is used, highly accurate adjustment is not possible. Therefore, it is possible to provide a high quality standard capacitor with a loss coefficient extremely close to zero.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing one embodiment of the present invention, and Fig. 2 is a circuit diagram showing an embodiment of the present invention.
The other side of the figure shows the actual circuit and equivalent circuit of the part common to the conventional configuration, Figure 3 shows the actual circuit and equivalent circuit of the compensation circuit part of Figure 1, and Figure 4 shows the actual circuit and equivalent circuit of the part of the compensation circuit in Figure 1. This is an equivalent circuit. C...Dielectric capacitor (defined capacitance), Ro...C8 of dielectric capacitor W filb FA low resistance 1
", L... Both terminals of dielectric capacitor "co, S...
・Electrostatic shield case, G...Ground terminal, CC...Dielectric capacitor 4J C8's ground capacity is gl
o g2 C, C2...Small capacity capacitor, R...Variable resistor, ZHL...Parallel impedance. Applicant's agent Sato-O R0 Figure 1 (q) (b) Figure 2

Claims (1)

[Claims] A first capacitor is housed in a shield case that also serves as a ground terminal, and a second and third capacitor are connected in series between both terminals of the first capacitor. A resistor is connected between the interconnection point of the second capacitor and the shield case, and
A three-terminal standard capacitor, characterized in that the third capacitor and the resistor provide the first capacitor with a negative parallel equivalent resistance that compensates for its loss coefficient.