JPH0125330Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a Jozefson voltage standard device that can measure and calibrate the electromotive force of a battery under test by comparing it with a standard voltage that applies the Jozefson effect.

FIG. 1 is a diagram showing an example of a conventional Josephson voltage standard device of this type. Liquid helium tank 2
A microwave 3 is irradiated onto the Josefson junction element 1 disposed in the. Element 1 causes a synchronization phenomenon at a voltage expressed by the following equation, and a step-like step symmetrical to the origin appears in the current/voltage characteristics of the junction as shown in FIG.

e _J = h/2e・no where o is the microwave frequency and n is an integer.
In each step, the output voltage e _J remains constant regardless of changes in the bias current supplied from the constant current source 4. The voltage divider 6 causes a constant current source 9 to flow a constant current through resistors 7 and 8 (voltage division ratio m) having a variable voltage division ratio, and generates two highly accurate comparison voltages that are related to each other. The output voltage i.e. Josephson voltage
e _J and the electromotive force of the battery under test 5 are compared in magnitude with the comparison voltage of the voltage divider 6, respectively. The difference in size is determined by galvanometers 10 and 11, respectively.
detected by. Galvanometer 10, 11
The output of can be recorded on a recorder 12 and the difference in voltage can be read. In this case, since the Josefson junction element 1 is in the liquid helium 2, a thermoelectromotive force E ₁ is generated in relation to the temperature difference from there to room temperature. For this reason, the polarity of the constant current sources 4 and 9 and the battery under test 5 are switched via switches 4a, 9a, and 5a to measure the thermoelectromotive force _E1 , so that the galvanometer 10 does not overrange.
This thermoelectromotive force E ₁ is canceled by a thermoelectromotive force compensation circuit 13 interposed between the Josefson junction element 1 and the galvanometer 10. The current of the constant current source 9 and the frequency o of the microwave 3 are adjusted appropriately to balance the outputs of the galvanometers 10 and 11 to zero. At equilibrium, the relationship e _S = m・e _J = m・n・o (1) holds between the electromotive force e _S of the battery under test 5 and the Josephson voltage e _J , so that the electromotive force e _S can be measured and calibrated.

However, e _J is usually about 1 to 10 mV, and to measure it with high precision, for example, 1 ppm or less, a resolution of 1 to 10 nV is required, but the drift of thermoelectromotive force changes with time, The amount of change becomes larger than the resolution, making it impossible to measure with an accuracy of 1 ppm or less. Further, since the calibration is based on an average value, measurement can be repeated several times, but the compensation circuit must be adjusted each time, which has the disadvantage that the operation is complicated and the measurement takes time.

The present invention aims to eliminate these drawbacks and realize a Josephson voltage standard device that can measure the electromotive force of a battery under test with high precision without being affected by thermoelectromotive force or drift of thermoelectromotive force. That is.

The present invention will be described in detail below with reference to the drawings.
FIG. 3 is a block diagram showing an embodiment of the Josefson voltage standard device according to the present invention. In FIG. 3, parts equivalent to those in FIG. 1 are given the same reference numerals, and their explanations will be omitted. 21 is a control circuit, switch 4
a, 9a and 5a to perform polarity switching. Numerals 22 and 23 are synchronous rectifier circuits that rectify the outputs of the galvanometers 10 and 11 in synchronization with the switch switching period, and are driven synchronously by the control circuit 21. The outputs of the synchronous rectifiers 22 and 23, that is, the synchronous rectified output signals, are sent to the recorder (or indicator) 12.
is output to. The thermoelectromotive force compensation circuit 13 adjusts to cancel the thermoelectromotive force to such an extent that the galvanometer 10 does not go into overrange.

In such a configuration, when thermoelectromotive forces E ₁ and E ₂ are generated as shown in the figure, switches 4a,
Even if 5a and 9a are switched, the polarities of the thermoelectromotive forces E ₁ and E ₂ do not change, so the synchronous rectification output signal is not affected by these thermoelectromotive forces E ₁ and E ₂ at all. Therefore,
While watching the display on the recorder (or indicator) 12, operate the synchronous rectifiers 22 and 2 in the same manner as in the conventional device.
Adjust so that the output of step 3 becomes zero. When balanced in this way, the relationship of equation (1) is established regardless of the thermoelectromotive forces E ₁ and E ₂ , and the battery under test 5 can be calibrated using the Josefson voltage e _J .

In addition, when adjusting the balance, first manually adjust the constant current source 9 so that the output of the synchronous rectifier 23 becomes zero,
Next, the current of the constant current source 4 and the frequency of the microwave are manually adjusted so that the output of the synchronous rectifier 22 becomes zero. ) and constant current source 9, automatic balance adjustment can be realized.

Furthermore, if the voltage division ratio m of the voltage divider 6 is configured to be arbitrarily variable, the frequency of the microwave is fixed, and after adjusting the constant current source 9 so that the output of the synchronous rectifier 22 becomes zero, the synchronous rectifier 23 It is only necessary to select the partial pressure ratio m so that the output of is zero, and the balance adjustment operation becomes extremely simple.

Furthermore, although the thermoelectromotive force compensation circuit 13 is used to prevent overrange of the galvanometer 10, it is not necessarily necessary and can be omitted if the galvanometer 10 has a sufficiently wide input range width.

As explained above, according to the Josefson voltage standard device of the present invention, the voltage balance can be adjusted without being affected at all by the thermal electromotive force generated in the detection circuit of the galvanometer and its temporal changes. This has the effect of simplifying the operation for measuring the electromotive force of the battery under test and loosening restrictions on environmental conditions such as ambient temperature.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing an example of a conventional Jozefson voltage standard device, Fig. 2 is a current/voltage characteristic diagram of a Jozefson junction element, and Figure 3 is a configuration diagram showing an example of the Jozefson voltage standard device according to the present invention. It is a diagram. DESCRIPTION OF SYMBOLS 1... Josephson junction element, 2... Liquid helium tank, 3... Microwave, 4, 9... Constant current source, 5... Battery under test, 6... Voltage divider, 7, 8...
...Resistor, 10, 11... Galvanometer, 12
... Recorder, E ₁ , E ₂ ... Thermoelectromotive force, 21 ... Control circuit, 22, 23 ... Synchronous rectifier circuit.

Claims (1)

[Scope of Claim for Utility Model Registration] A Josephson junction element that is disposed in a liquid helium tank and generates a Josephson voltage according to the bias current when a constant bias current is supplied and microwaves are irradiated, and a switch. The polarity is switched in relation to
The voltage value is variable and the voltage ratio is kept at a predetermined ratio 2
a voltage divider that generates two comparison voltages; a thermoelectromotive force compensation circuit that compensates for the thermoelectromotive force generated in the Josefson junction element; and one comparison voltage of the voltage divider and the thermoelectromotive force compensation circuit that It consists of one galvanometer that detects the difference between the thermoelectromotive force and the compensated Josefson voltage, and the other galvanometer that detects the difference between the other comparison voltage of the voltage divider and the battery under test, and the comparison voltage and The electromotive force of the battery under test can be determined based on the voltage ratio, the comparison voltage, and the output of the other galvanometer by adjusting the frequency of the microwave to balance the output of the one galvanometer to zero. The voltage standard device includes a control circuit that periodically switches the polarity of the bias current, the polarity of the comparison voltage generated in the voltage divider, and the connection of the battery under test; and the control circuit controls the outputs of the two galvanometers according to the switching period. A Josephson voltage standard device characterized in that it is equipped with a synchronous rectifier circuit that rectifies each in synchronization with each other.