JPH0772184A - Output voltage measuring instrument of thermoelectric type ac/dc converter - Google Patents

Abstract

PURPOSE:To perform an accurate measurement in the order of ppm by measuring the output voltage of a thermoelectric type AC/DC converter which is connected to a comparison measuring circuit of the difference between AC and DC by measuring it according to the oscillation frequency by applying it to Josephson junction oscillator instead of measuring it with an accurate digital voltmeter. CONSTITUTION:In output voltage measuring instrument of a thermoelectric type AC/DC converter which is connected to the comparison measuring circuit of the difference between AC and DC of two thermoelectric type AC/DC converters, a thermoelectric type AC/DC converter 1 is connected to Josephson junction oscillator 4 via a thermal EMF fluctuation eliminator 2 and a voltage divider 3 and the frequency from the oscillator 4 is detected by a frequency detector 5, thus the output voltage of the thermal electric type AC/DC converter 1 is measured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an output voltage measuring device for a thermoelectric type AC / DC converter which is used when performing precise measurement of AC voltage and AC current.

[0002]

2. Description of the Related Art In order to measure a low frequency AC voltage (current) with precision, it is necessary to compare the low frequency AC voltage (current) with a DC voltage (current).

Conventionally, for this comparison, a current is passed through a resistance wire (heater), and the temperature rise is detected by a thermocouple.
A so-called thermoelectric AC / DC converter is used. This thermoelectric type AC / DC converter is classified into a single thermoelectric type thermoelectric type AC / DC converter and a large number of thermocouple type thermoelectric type AC / DC converters depending on the number of thermocouples used. The effective value of the AC voltage (current) is obtained by applying a current) and comparing the output with a DC voltage (current) having the same thermoelectromotive force.

At the time of this comparison, a slight difference occurs between the AC voltage and the DC voltage, which is called the AC / DC difference of the converter. The smaller the AC / DC difference, the more accurate the measurement.

A low-frequency AC voltage (current) is measured by measuring the AC / DC difference. In this case, the low-frequency AC voltage is measured by combining a thermoelectric AC / DC converter and a series resistor. Only thermoelectric type AC / DC converters are used for frequency AC current measurement, and these are said to be standard devices for low frequency AC voltage or current measurement.

[0006] It is necessary to select a value of the AC / DC difference of the standard device that is as small as possible in order to improve the precision of the precision measurement of the low-frequency AC voltage (current). Since a constant value cannot be obtained, therefore, a precision measuring device for low-frequency AC voltage (current) uses a comparative measuring device consisting of a measuring circuit in which a plurality of (N) standard devices are connected in parallel. Select any two sets of standard equipment from among the standard equipment, connect them to a precision power source, measure the difference in the AC / DC difference of these two sets of standard equipment, and perform this operation for all the standard equipment. The (current) standard is maintained.

FIG. 2 shows a conventional AC / DC difference comparison measuring device for precision measurement of low-frequency AC voltage. TVC ₁ and TVC ₂ are standard devices that connect a thermoelectric AC / DC converter and a series resistor. Standard TV
The measurement circuit of C ₁ and TVC ₂ connected in series Precision AC power source (V
_a), from Precision DC power supply _{(V d), V a,} V d +, V d -,
It is applied with V _a and a changeover switch, and the thermoelectromotive force of both standards is measured with precision digital voltmeters DVM1 and DVM2. At this time, the controller performs power switching, data handling, and calculation of the difference between the AC and DC.

[0008]

In the conventional comparative measuring device as described above, the thermoelectromotive force of the standard devices TVC ₁ and TVC ₂ is expensive, and it is measured by the precise digital voltmeters DVM1 and DVM2 to determine the AC / DC difference. I was measuring the difference.

However, in the measurement, alternating current and direct current are flowed alternately so that the thermoelectromotive forces generated in the standard device TVC ₁ are equal, but the short-term stability of the precision alternating-current power supply (V _a ) is
Since it is about 0.007% in 10 minutes, this operation is extremely difficult.

Further, the thermal time constant of the standard device is several seconds, and until the thermoelectromotive force becomes stable by applying a current (voltage) to the standard device.
After 30 seconds or more, the thermoelectromotive force is measured.It is extremely difficult to match the thermoelectromotive force to the same level as the difference in the AC / DC difference is stabilized at about ppm (parts per million). .

Further, in practice, digital voltmeters DVM1 and DVM2
However, there are fluctuations, and for this reason, it is expensive, and even if the precision digital voltmeters DVM1 and DVM2 are used, the measurement accuracy is limited.

[0012]

In order to solve the above-mentioned problems, according to the present invention, an output voltage measuring device for a thermoelectric type AC / DC converter connected to an AC / DC difference comparison circuit of two thermoelectric type AC / DC converters. In, the thermoelectric type AC / DC converter is connected to a Josephson junction oscillator via a thermal EMF fluctuation remover and a voltage divider, and the frequency from the oscillator is detected, from which the output of the thermoelectric type AC / DC converter is obtained. The present invention proposes an output voltage measuring device for a thermoelectric AC / DC converter that measures voltage.

[0013]

That is, as shown in FIG. 2, conventionally, the output voltage of the thermoelectric type AC / DC converter connected to the AC / DC difference comparison / measurement circuit was measured by a precise digital voltmeter. Rather than measuring with a voltmeter, the output voltage of the thermoelectric AC / DC converter is divided and applied to a Josephson junction oscillator, and the applied voltage is measured from this oscillation frequency. Can be measured.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiments. 1 is a pair of thermoelectric type AC / DC converters connected to an AC / DC difference comparison / measurement circuit as shown in FIG. 2 and 2 is a thermal EMF.
A fluctuation remover, 3 is a voltage divider, 4 is a Josephson junction oscillator, 5 is a frequency detector, and 6 is a display.

Here, as the thermoelectric type AC / DC converter 1, any one of a single thermocouple type thermoelectric type AC / DC converter and a large number of thermocouple type thermoelectric type DC / DC converters can be used.

Since the Josephson junction oscillator 4 is placed at a super low temperature using liquid helium or the like in order to perform an appropriate oscillation operation, the Josephson junction oscillator 4 and the thermoelectric element placed at room temperature are Fluctuation of thermoelectromotive force (thermal EMF) is generated in the lead wire connecting the die AC / DC converter 1. In the present invention, the thermoelectric AC / DC converter is used to remove the fluctuation of the thermo EMF in the lead wire. A thermal EMF fluctuation eliminator 2 composed of, for example, a vacuum system is provided between the voltage divider 1 and the voltage divider 3.

The output voltage of the thermoelectric AC / DC converter 1 is divided by the voltage divider 3 and applied to the Josephson junction oscillator 4 in order to make the Josephson junction oscillator 4 oscillate properly.

There are various methods of voltage division, but in the present invention, a precise voltage division method is adopted, and the voltage divider 3 is, for example, an accurate Hamon voltage divider or a voltage divider. A series resistance voltage divider capable of calibrating the pressure ratio can be used according to its advantages.

As the Josephson junction oscillator 4, there are a point contact type, a bridge type, a stripline type, an array type and the like, but any type can be used as long as it oscillates at a frequency corresponding to an applied voltage. Can be used.

The frequency oscillated by the Josephson junction oscillator is detected by the frequency detector 5. This detector 5 may be composed of an impedance matching IC circuit and can count the frequency SQUID (Superconducti).
ng Quantum Interference Device: superconducting quantum interference device).

Finally, the detected frequency is displayed 6
The voltage applied to the Josephson junction oscillator can be known by displaying on.

For other thermoelectric AC / DC converters connected to the AC / DC difference comparison / measurement circuit, the voltage applied to the Josephson junction oscillator can be measured in a similar manner. The difference in AC / DC difference between the two thermoelectric type AC / DC converters connected to the circuit can be measured through the two-system calculation processing device.

Since the Josephson junction oscillator 4 can obtain a high frequency with a line width of 0.1 ppm,
By using the thermal EMF fluctuation eliminator 2 and the voltage divider 3 of the present invention having higher precision,
It is possible to measure the difference in AC / DC difference between individual thermoelectric AC / DC converters with an accuracy of 0.1 ppm or better.

[0024]

In summary, according to the present invention, the output voltage of the thermoelectric type AC / DC converter connected to the AC / DC difference comparison / measurement circuit is not measured by a precise digital voltmeter, but divided by Joseph. Since it is applied to a Son-junction oscillator and measured from this oscillation frequency, precise measurement can be performed in the ppm order.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is an AC / DC difference comparison circuit diagram of a conventional thermoelectric AC / DC converter.

[Explanation of symbols]

TVC ₁ , TVC ₂ Standard (thermoelectric type AC / DC converter) V _a Precision AC power supply V _d Precision DC power supply DVM1, DVM2 Precision digital voltmeter 1 Thermoelectric type AC / DC converter 2 Thermal EMF fluctuation remover 3 Voltage divider 4 Josephson Junction Oscillator 5 Frequency Detector 6 Display

Claims (1)

[Claims] 1. An output voltage measuring device for a thermoelectric type AC / DC converter connected to a circuit for comparing and measuring the AC / DC difference of two thermoelectric type AC / DC converters, wherein the thermoelectric type AC / DC converter is subjected to thermal EMF fluctuation removal. Connected to a Josephson junction oscillator via a voltage divider and a voltage divider, the frequency from the oscillator is detected, and the output voltage of the thermoelectric type AC / DC converter is measured from this frequency. Output voltage measuring device for AC / DC converter.