JP2595679Y2 - Attenuator frequency characteristic correction circuit - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an attenuator circuit for an AC voltage measuring instrument. More specifically, the present invention relates to an attenuator frequency characteristic correction circuit.

[0002]

2. Description of the Related Art An example of a conventional attenuator will be described with reference to FIG. 2. The voltage dividing resistors R11, R12 to R1n and the capacitors C11, C12 to C1n for correcting frequency characteristics are shown in FIG.
It comprises a range switching relay S11, S12 to S1n and a buffer amplifier 11.

It is generally known that the flattening of the frequency characteristics of an attenuator circuit can be achieved by making the attenuation of the resistance component equal to that of the capacitance component. The resistance attenuation ratio is the impedance ratio of only the resistance component divided by the attenuator, and the capacitance attenuation ratio is the impedance attenuation ratio of only the capacitance component divided by the attenuator. That is.

In order to adjust the attenuator circuit flat to a high frequency range, a capacitance attenuation ratio including a relay contact capacitance, a wiring storage capacitance, and a storage capacitance Cs1 composed of an input capacitance of the buffer amplifier 11 included in the attenuator circuit. And the resistance attenuation ratio need to be adjusted to be the same. For this purpose, a known low-frequency and high-frequency signal source is applied to correct the C12, C13 to C1n correction capacitors,
For example, adjustment was made by turning a trimmer capacitor or the like.

The conventional problem is that the setting of the frequency characteristic correction for each range is set with high accuracy (for example, an error of less than 0.01%).
However, the conventional circuit means has a disadvantage that the adjustment takes a lot of time. The cause is a circuit in which a plurality of trimmer capacitors are connected in series. Therefore, if adjustment is made even at one point, the capacitance set value of another range already adjusted is lost. Therefore, it is necessary to repeatedly adjust the entire range a plurality of times to gradually converge to the target accuracy.

[0006]

[Problem to be solved by the invention] The problem to be solved by the invention is to make it easy to adjust the frequency characteristic correction of the attenuation of the attenuator without affecting the setting of other ranges. An object of the present invention is to realize correction of characteristics.

[0007]

According to the present invention, the above-mentioned problems are solved by the following means. A plurality of attenuation resistors R11 to R1n for attenuating the AC voltage input;
A plurality of frequency characteristic correcting capacitors C11 to C1n
And an attenuator including a plurality of range switching relays S11 to S1n, a buffer amplifier 11, and an AC voltage measuring unit 12, have the following configuration.

The control circuit comprises a variable amplifier 13, a correction resistor Ra, a correction value memory 15, and a control unit 14. The input of the buffer amplifier 11 is connected to the output of the attenuator and one end of the correction resistor Ra. The output of the buffer amplifier 11 is connected to the input of the variable amplifier 13, the output of the variable amplifier 13 is connected to the other end of the correction resistor Ra, and the content of the correction value memory 15 is connected to the variable amplifier 13 via the control unit 14. I do. The correction value memory 15 stores set value data set in the variable amplifier 13 for each measurement range. A frequency characteristic correction circuit for an attenuator comprising the frequency characteristic correction means as described above.

In the above configuration, the variable conductance amplifier 13 shown in FIG.
C and the correction data read from the correction value memory 15 are D /
A frequency characteristic correction circuit for an attenuator, comprising means for setting an A converter 13a, performing constant current conversion 13b, and varying an amplification degree by a variable conductance amplifier 13c.

A frequency characteristic correction circuit for an attenuator, wherein the same function is realized by changing the input of the variable amplifier 13 to the input side of the buffer amplifier 11 as shown in FIG. .

[0011]

The variable resistor has a function of a variable resistor. That is, when the amplification degree of the variable amplifier 13 is changed, the potential difference between both ends of the correction resistor Ra changes,
The current flowing through the correction resistor Ra changes according to the amplification degree. This equivalent variable resistance is combined with the resistance value of the attenuator, and becomes the actual resistance attenuation ratio of the attenuator. And
By setting and controlling the resistance attenuation ratio to match the capacitance attenuation ratio, frequency characteristic correction is realized.

The correction value memory 15 serves to store frequency characteristic correction data for each range. The frequency characteristic correction for each range is performed by using the above-described variable resistance function for each range, obtaining frequency characteristic correction data, and obtaining a correction value memory 1.
Save it in 5. When using, the correction value memory 15
Then, the correction data is taken out of the variable amplifier 13, and the correction data is set in the variable amplifier 13, thereby correcting the frequency characteristic in the range.

[0013]

1 and 3 show an outline of the internal configuration of a variable amplifier 13. FIG. Here, the buffer amplifier 11, the variable conductance amplifier 13c, and the output amplifier 13e of the AC amplifier to be used use elements having cutoff frequency characteristics sufficiently higher than the upper limit frequency to be used, for example, several tens times or more. For the range switching relay, for example, a lead relay or a semiconductor analog switch is used.

The internal configuration of the variable amplifier 13 includes a D / A converter 13a, a constant current converter 13b, a variable conductance amplifier 13c, an IV conversion resistor 13d, an output amplifier 13
The variable amplifier is realized by setting an arbitrary value for data from the control unit 14. Here, the variable conductance amplifier is an amplifier whose gm (transfer coefficient) changes depending on the bias current of the amplifier.

The procedure at the time of calibration will be described with reference to the flowchart of FIG. 5. The range is first switched to one of the ranges. A reference voltage having a frequency sufficiently lower than the frequency determined by the CR time constant of the attenuator (to such an extent that does not affect the calibration accuracy) is input and read by the AC voltage measuring unit 12.

Next, a reference voltage having a frequency sufficiently higher than the frequency based on the CR time constant of the attenuator (about the frequency at which the buffer amplifier and the variable amplifier do not depend on the frequency) is input. read.

If the difference between the two measured voltages is outside the target accuracy error range, a correction value is calculated from the difference value, set in the variable amplifier 13, and measured again. When the difference between the two measured voltages falls within the target accuracy error range, the set data is stored in the correction value memory 15 as frequency characteristic correction data of the range. The control unit 14 automatically performs a series of these operations.

With the same operation, the other ranges are also calibrated and stored in the correction value memory 15. Here, the value of the attenuation in each range is also stored in the correction value memory, but the description is omitted because it is not directly related to the frequency characteristic correction.

[0019]

As described above, according to the present invention, since the adjustment function for correcting the frequency characteristics is connected after the range switching relay, independent adjustment can be performed for each range, and adjustment of other ranges can be performed. Does not affect Also,
The adjustment only needs to be performed once for each range. This eliminates the task of adjusting to a predetermined accuracy while repeatedly performing the conventional adjustment, and the adjustment time can be reduced. Also, a predetermined setting accuracy can be easily realized.

[0020]

[Brief description of the drawings]

FIG. 1 is a block diagram of the present invention.

FIG. 2 is a conventional block diagram.

FIG. 3 is a block diagram of an embodiment.

FIG. 4 is a connection form diagram of a variable amplifier.

FIG. 5 is a flowchart of a calibration procedure.

[Explanation of symbols]

 C11 to C1n Correction capacitor R11 to R1n Voltage dividing resistor S11 to S1n Range switching relay 11 Buffer amplifier 12 AC voltage measurement unit 13 Variable amplifier 14 Control unit 15 Correction value memory Ra Correction resistance 13a D / A converter 13b Constant current conversion 13c Variable Conductance amplifier 13d IV conversion resistor 13e Output amplifier

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H03G 5/02 G01R 19/00 H03F 1/34 H03H 11/46

Claims (2)

(57) [Scope of request for utility model registration] An attenuator comprising a plurality of voltage dividing resistors for attenuating an AC voltage input, a plurality of correction capacitors, a plurality of range switching relays, and an output signal of the attenuator.
Buffer amplifier to which a signal is applied, and the buffer amplifier
AC voltage measuring unit (12) for measuring the output signal of
The circuit includes a variable amplifier (13), a correction resistor (Ra), a correction value memory (15), and a control unit (14). The input of the buffer amplifier (11) has an output of an attenuator.
One end of the correction resistor (Ra) is connected, the output of the buffer amplifier (11) is connected to the input of the variable amplifier (13),
The output of the variable amplifier (13) is connected to the other end of the correction resistor (Ra), and based on the output signal of the AC voltage measurement unit (12)
The frequency correction data for each range is transmitted via the control unit (14).
The correction value memory (15) stored in advance by the control unit (14)
A frequency characteristic correction circuit for an attenuator, comprising frequency characteristic correction means connected to the variable amplifier (13) via the circuit. 2. The variable amplifier according to claim 1, wherein the variable amplifier has an internal configuration for each range based on an output signal of the AC voltage measurement unit.
Correction value memory (1 ) in which the frequency correction data of
Convert the correction data read from 5) to an analog signal
Transmitting a D / A converter (13a), the output signal of the D / A converter (13a) that
Variable conductance amplifier with variable coefficient (13c)
A frequency characteristic correction circuit for an attenuator, comprising: