JPH04147063A - Precision comparator for thermoelectric ac-dc converter - Google Patents

Abstract

PURPOSE:To automate a procedure and prevent erroneous operation by performing all of control, measurement and determination of results by means of a controller and a calculator. CONSTITUTION:Frequency setting of a precision ac power source 1, current setting of a precision dc power source 2 and switching of a plurality of switches S0 to S3 of a power switcher 3 and standards are performed by a controller 4. Measurement of precision digital voltmeters DVM1, DVM2 and determination of measurement results are performed by a calculator 5. When a programmable power source is to be used as the power source 1, the frequency setting is done by software. Thus erroneous operation by a manual task is prevented. This automation allows comparison and measurement of all combinations of a plurality of converters in a short time, so that two specific converters which are most preferable can be selected.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a comparison device for a thermoelectric AC/DC converter used for precision measurement of AC voltage, AC current, etc.

(Prior Art) In DC measurement, the voltage standard is given by a Josephson voltage standard device, but in AC measurement, there is no device that generates a known alternating current voltage (li current), so the alternating voltage (current) For precision measurement, use a device that can obtain equal outputs when the measured voltage and the equivalent DC voltage (current) are input alternately, and convert the effective value of the measured voltage (current) into a known DC voltage (current). The method used is to compare and determine the Devices used in this method include an AC/DC converter that converts an AC amount into a DC amount and an AC/DC comparator that compares the amount with the DC amount.

Since it is possible to obtain a precise DC amount, the accuracy of this method is mainly determined by the errors in AC/DC conversion and AC/DC comparison. These errors are sometimes referred to as AC/DC differences, and determining AC/DC differences is used almost interchangeably with establishing AC voltage (current) standards.

Regarding low-frequency AC current and voltage standards, attempts have been made to use a thermoelectric AC/DC converter (TE) that uses thermoelectric phenomena and an electrostatic AC/DC comparator that uses an electrostatic torque balance meter. Comparing them from a practical standpoint, thermoelectric AC/DC converters (TE) have a simple structure and are easy to handle, so they have high practical value as low-frequency AC (hereinafter referred to as AC) current/voltage standards. .

This thermoelectric type AC/DC converter has resistance &! A current is passed through a heater (heater), and a thermocouple detects the temperature rise.

The AC/DC difference δ of a thermoelectric type AC/DC converter is an AC current with an effective value of ■, and 1. Suppose that when direct currents of the same magnitude are passed alternately, the same amount of output is obtained.

δ= f I , -1,)/I,
Defined in (1).

A precise comparison of the two transducers is made by measuring the difference in their orthogonal differences.

Conventionally, the difference in AC/DC difference of a thermoelectric AC/DC converter is measured based on the principle of the two-voltmeter method. FIG. 5(A) shows a connection method when comparing currents using this method.Transducers TEI and TE2 are connected in series with a connector, and are connected to a power source through a coaxial line. Therefore, when the same current flows through these converters, the thermoelectromotive force E of both converters is measured simultaneously using a precision digital voltmeter (DVMI, DVM2+), and the difference in AC/DC difference is determined by computer processing. Note that TE2 is placed on the power supply side. The thermal environment changes and the measurement results differ.

FIG. 5(B) shows the connection method for voltage comparison; the converter is the same as that used for current comparison. Therefore, a resistor corresponding to the rated voltage is required. Connect the two pairs of converters and resistors as shown in the figure, apply the same voltage, measure the thermoelectromotive force E of both with a precision digital voltmeter in the same way as the current comparison, and calculate the AC/DC difference. The difference is calculated by computer processing.

Assume that the current AC/DC difference δ,, TE,2 is the AC/DC difference δ2, and calculate the DC input to TE. Then, the difference between the AC and DC differences (δ1
-62) is approximately given by the following formula according to the principle of the two-voltmeter method.

δ1-δ, = ((E,,-E,,)/ΔEd□-(E
□-Ell,)/ΔE,,) ・ΔI, l/I,
(2) Here, El and E ax are effective values of 1. The alternating current becomes converter TE1. When flowing to TE2, T
El, thermoelectromotive force generated at TE2, E a+, Ed2 is d, when direct current is passed through the converter, TE2,
The thermoelectromotive force generated at TEI and TE2, ΔE, and ΔEo indicate the change in the thermoelectromotive force at TE2 relative to a minute change in DC current ΔI6.

Note that voltage comparison can also be expressed by a similar formula.

On the other hand, converters and resistors such as those shown in Figure 5 (A) and CB) change over time, so in order to maintain standards, use a converter for current measurement and a converter for voltage measurement. It is necessary to configure a large number of standard device groups using resistors, and select two specific standard devices from among these groups in order to compare and measure these standard device groups. Figure 5 (C) is a combination diagram when two specific standards are taken out of a group of six standards and used for mutual comparison. shows.

FIG. 6 shows a circuit configuration for measuring the AC/DC difference by current measurement using the two-voltmeter method, in which a switch S11 is used to connect the precision AC power source V to the standard device TE1. Apply AC current to TE2, and use switches S1□ and SL to apply DC current from DC power source v6. Test the other standard device (called a test device) using one standard device as a reference, and perform the test as described above. Select two specific standards TE1 from a large group of standards. Select TE2.

In addition, the setting of the DC current I6 is done as follows. Add the rated AC current of a certain frequency to the tester TEI, measure the thermoelectromotive force E with a precision digital voltmeter fovM11, and then connect it to the DC if source. Then, add direct current in the forward direction and the same direction in the reverse direction. In these two times, the thermoelectromotive force of the tester is averaged, and the DC power source is adjusted so that this average becomes equal to the value of the thermoelectromotive force when the above-mentioned alternating current is applied.

AC current, DC current in the forward direction, DC current in the same direction, AC current in the same direction are applied in sequence, and this cycle is repeated several times.
Measure the thermoelectromotive force of 2. This allows the average E M
Find l, E ax, E, , E, □.

Thereafter, the slope of the input current thermoelectromotive force characteristics of TEl and TE2 is changed by the switch S14. , △E, □/Δ
I6 is measured, and based on the above measurements, the difference in cross-direction difference (δ1-δ,) is calculated from equation (2).

After completing the above measurements, repeat the above series of measurements using the same rated AC current and changing the frequency for the same standard combination.

(Problem to be solved by the invention) However, in the conventional comparator as described above, the frequency settings etc. are done manually, which requires a great deal of effort and time, and furthermore, this can lead to malfunctions. It was also the cause of

In addition, the work of selecting two specific standards by taking out two standards from each of the large group of standards mentioned above, comparing and measuring them, and selecting two specific standards is done manually. This required a great deal of effort and time, and also caused malfunctions.

(Means for Solving the Problems) In order to solve the above problems, the present invention includes an AC power source, a DC power source, the power supply switching device, a plurality of thermoelectric AC/DC converter groups, and the converter. Control and calculation for the selection switch of the device group, the precision voltmeter, the voltage and frequency of the AC power supply, the current setting of the DC power supply, the switching control of the power supply selector and the selection switch, the measurement of the comparison device, and the judgment of the measurement results. This paper proposes a comparison device for thermoelectric AC/DC converters consisting of a thermoelectric converter.

Here, a programmable power source can be used as the AC power source or the DC power source.

In the case of current comparison, a contact is connected to the converter to function as a selection switch, and in the case of voltage comparison, a contact is connected to the converter via a resistor to function as a selection switch.

(Function) In summary, according to the present invention, the voltage and frequency of the AC power supply, the current setting of the DC power supply, the switching control of the power supply selector and the selection switch, the measurement of the comparison device, and the judgment of the measurement results are all controlled and calculated by the computer. Since this is done manually, there is no need for the hassle of manual work as in the past, and malfunctions can therefore be prevented.

Further, according to the present invention, it is possible to compare and measure all combinations of a plurality of converter groups in a short time and select the two most preferable specific converters.

Furthermore, in this invention, by configuring a selection switch by connecting contacts to the converter directly or through a resistor, wiring is fixed, operation is reliable, measurement accuracy is improved, and malfunctions can be prevented. etc. can be prevented.

Furthermore, by using a programmable power source as a power source, it is possible to set the voltage and frequency.

(Example) FIG. 1 is a diagram showing the relationship between a standard device group consisting of a resistor and a converter and a switch in the case of voltage comparison in the present invention.
A row of contacts indicated by black dots in the figure is provided at both ends of the standard device, and a switch S1. S2 is provided, and switches S3 and S4 are provided at the other end of the contact row, and switches S1 and 33 and switches S2 and 34 are mechanically coupled, respectively, so that standards with the same number can be selected. For example, in accordance with the combination sequence shown in FIG. 5(C) for a group of N standard devices, switches Sl and 3 are
3 is connected to the fifth standard, and switches S2 and 54 are connected to the second standard, and in this state the same voltage is applied from the precision power supply.

FIG. 2 is a diagram showing the relationship between a standard device group consisting of converters and switches in the case of current comparison in the present invention.The relationship between the contact array and switches with respect to the standard device is the same as in FIG. Connection methods are different. That is, as shown in FIG.
Switch SL according to the combination rules shown in Figure (C)
and S3 for the fifth, and switches S2 and 54 for the second F! Select the standard, and the current is switch Sl - standard J - switch S
3-Switch S2→Standard device→Switch S4. That is, the same current is made to flow in both standards J and K in the same direction.

Note that even if switches Sl and S3 and S2 and S4 select the contacts of the same standard and short, a resistor (not shown) with a resistance value greater than the internal resistance of the standard must be inserted on the power supply side. to avoid damaging the equipment.

Also, after connecting the power supply to the dummy resistor with switch SO,
The switches 51 to S4 may be changed over.

FIG. 3 shows a more specific wiring diagram in the case of voltage comparison, and a group of N standard devices consisting of converters and resistors has a contact array from switches 51 to S4. (C1
Switches S1 and 33 select the 5th standard, and switches S2 and 34 select the 5th standard according to the combination rules shown in Figure 1.In order to measure the thermoelectromotive force of standard J, switch S5 selects one precision digital voltmeter (Fig. (not shown) to the output terminal of standard J. Similarly, switch S6 connects another voltmeter (not shown) to the output terminal of the standard. Here, switches S5 and 56 are used that have low noise and good reproducibility. Also, the switches S3 and 54 are the switches St and 3.
Since the switches S1 and S32 are interlocked, there is no need to move them for voltage measurement, but for current measurement, it is necessary to move them independently of switches S1 and 32.

Incidentally, since the combinations for comparison measurement are sequentially changed to J, then N, and L, the L-th standard is preheated sufficiently necessary for measurement using switch S7 before measurement.

FIG. 4 is a schematic diagram of a comparison device according to the present invention, and 1
is a precision AC power supply consisting of a programmable power supply, 2 is a programmable precision DC power supply, 3 is a power switch, 4 is a controller, 5 is a calculator, DVMI and DVM2 are precision digital voltmeters, 5O1S1. S2, S3/4: Indicates the switches of the L standard equipment group.

In addition, the frequency setting of the precision AC power supply 1, the current setting of the precision DC power supply 2, the changeover device 3 and the switches 5O1S1, S2
, S3... is controlled by the controller 4 using a precision digital voltmeter DVM! The measurement of the DVM 2 and the judgment of the measurement results are performed by the calculator 5. When a programmable power supply is used as the 6-electrode AC power supply 1, the frequency setting is performed by software.

Next, a procedure for measuring the difference between the cross and cross directions using this comparator will be described, but since this has been described in detail previously, only an outline will be shown here.

(a) As shown in FIGS. 1 to 3, two specific standards are selected from a group of standards.

(b) Next, set the rated AC voltage of a certain frequency to the AC power supply l, and after sufficiently preheating the two selected standard devices, measure the thermal electromotive force of the test device with a precision digital voltmeter DVMI. Next, change the connection to the DC power supply 2 and take the average value of the thermoelectromotive force in the DC forward direction and reverse direction. This average value is made to be somewhat equal to the above-mentioned AC thermoelectromotive force. Adjustment of thermoelectromotive force is performed by changing the voltage of the DC power supply, which is adjustment of thermoelectromotive force.

(c) To further describe the measurement of the alternating difference, this cycle of alternating current, direct current, reverse direction, and alternating current is repeated several times, and then the above measurement is repeated from the standard thermoelectromotive force adjustment using the marker resistor.

(Effects of the Invention) In summary, according to the present invention, control is performed using X devices;
Since all measurements and result judgments are performed, there is no need for the hassle of manual work as in the past, and malfunctions can be prevented.

Further, according to the present invention, it is possible to select the two most preferable specific converters by comparing all combinations of a plurality of converter groups in a short time.

Furthermore, the wiring is fixed, operation is reliable, and measurement accuracy can be improved.

[Brief explanation of drawings]

FIG. 1 shows a standard selection circuit for voltage comparison in the present invention, and FIG. 2 shows a standard selection circuit for current comparison.
Figure 3 is a more specific wiring diagram for voltage comparison;
The figure is a schematic diagram of the comparison device according to the present invention, Figure 5 (A) is a diagram showing the connection method for current comparison and the configuration of the standard device group, and Figure 5 (B) is the connection method for voltage comparison. FIG. 5C is a diagram showing an example of a combination rule for six standard device groups, and FIG. 6 is a diagram showing a conventional comparison device. In the figure, l is a precision AC power supply, 2 is a DC power supply, 3 is a power off back cover, 4 is a controller, 5 is a calculator, DVMI and DVM2 are precision digital 9) Li voltmeters, so, si, S2, S3・
... is a switch of the standard equipment group. Figure 1 Figure 2 Figure 4 Figure 5 (C) Figure 5 (B) Figure 5 (A)

Claims (4)

[Claims] (1) An AC power supply, a DC power supply, the power supply switching device, a plurality of thermoelectric AC/DC converter groups, a selection switch for the converter group, a precision voltmeter, and the voltage and frequency of the AC power supply. A comparison device for a thermoelectric AC/DC converter, characterized in that it comprises a control/calculator for setting the current and voltage of the DC power source, controlling the switching of the power supply selector and selection switch, measuring the comparison device, and determining the measurement results. (2) The comparison device according to claim 1, which uses programmable power supplies as the AC power source and the DC power source. (3) The comparison device according to claim 1, wherein a contact is connected to the converter to serve as a selection switch. (4) The comparison device according to claim 1, wherein a contact is connected to the converter via a resistor to form a selection switch.