Quantum voltmeter (PJVS)

Programmable Josephson voltage standard system enables high-precision voltage measurements (DC up to 100 kHz)

The AC quantum voltmeter is a programmable Josephson voltage standard system, optimized for use in high-precision measurement technology within the range of DC up to 100 kHz.

It was developed by the Physikalisch-Technische Bundesanstalt Braunschweig (PTB) in collaboration with esz AG and Supracon AG.

The primary standard for DC and AC voltages enables the automated calibration of:

  • Secondary standards
  • Fluke calibrators
  • Linearity and nonlinearity of voltmeters
  • Multijunction thermal converters

Based on the reference resistor, automated current and resistance calibrations can be performed in both DC and AC voltage ranges. In addition, direct access to individual components via a TCP protocol allows users to develop their own calibration routines.

Versions

System cooler AC/DC

System Helium AC/DC

System Helium DC

Specifications

  • Typical calibration accuracy (direct comparison with a second Josephson voltage standard)
  • ±1 nV at 10 V
    ΔV/V10V = 1×10-10
  • Typical calibration accuracy of DC voltage standards, e.g. Fluke 732B (limited by the noise of the DC voltage standard)
  • ±100 nV at 10 V
    ΔV/10V = 1×10-8
  • Typical calibration accuracy (direct comparison of two Josephson waveforms with 4 samples)
  • ±200 nV @ 20 VPP, 1 kHz
    ΔV/V = 2×10-8
  • Typical calibration accuracy of calibrators, e.g. Fluke 5720A (limited by the noise of the calibrator)
  • ΔV/V = 5×10-7 @ V ≤ 7.1 V(rms), f ≤ 1 kHz, 1 min measurement time
    ΔV/V < 3.5×10-6 @ V ≤ 1 V(rms), f ≤ 100 kHz (using the new sampling mode)

PJVS Array

The AC quantum voltmeter, featuring a programmable 10-volt Josephson voltage standard circuit at its core, offers the following performance characteristics:

  • 69,632 Josephson junctions 
  • ±10.08 V maximum output voltage 
  • 70 GHz microwave frequency 
  • min. 1 mA step width of the first-order Shapiro step 
  • ±6 mA base current 

V = n × f / KJ90

V = Josephson voltage

KJ90 = Josephson constant

n = programmable integer value

f = microwave frequency

Applications

Via a TCP interface, the quantum voltmeter and quantum calibrator can be externally controlled through software to create custom applications. This provides additional possibilities for automated calibrations in cases where the required configuration is not available as a standard option.

  • Fluke calibrator

    The Fluke calibrator, available in versions 5700A, 5720A, or 5730A, can be used fully automatically for DC and AC voltages as well as for DC and AC currents. The current calibration is based on the use of reference resistors.

    DC Current Calibration

    AC Current Calibration

  • Zener reference

    As an additional option, Zener references can be calibrated automatically. For this purpose, three voltages or three Zener references are connected simultaneously to the multiplexer and measured sequentially. The user can flexibly decide how many measurement points should be taken.

  • Voltmeter

    With the voltmeter, linearities and nonlinearities can be automatically determined for a wide range of well-known voltage meters — both across entire ranges and within specific voltage ranges. Measurements can be performed using either the system’s standard settings or user-defined configurations. This allows users to flexibly determine at which voltage levels measurements should be taken, or whether specific voltmeter settings (NPLC, filter, number of readings) should be used for data acquisition. 

  • Thermal converter

    For the characterization of thermal converters (TC) and AC/DC transfer standards, the voltmeter "Quantum Calibrator" — based on the updated AC Quantum setup — is available.

    The Quantum Calibrator is used for the calibration of thermal converters and AC/DC transfer standards at low frequencies (10 Hz to 2 kHz) and for voltages up to 7 VRMS.

    The following thermal converters and AC/DC transfer standards are suitable for characterization:

    1. Single-junction thermal converters (SJTCs)
    2. Planar multijunction thermal converters (PMJTCs)
    3. AC/DC transfer standards, e.g. Fluke 792A

    DC Current Calibration

    AC Current Calibration

  • Resistance ratio

    The calibration of resistors is possible with the "AC Quantum Calibrator" upgrade. In this measurement mode, a voltage source such as the Fluke 57XX calibrator is applied to two resistors connected in series to measure the voltage drop across each resistor sequentially using the AC Quantum Voltmeter. If the value of one resistor is known, the other can be precisely determined from the ratio of the voltage drops.

    DC Current Calibration

    AC Current Calibration

  • Voltage divider

    It is possible to measure voltage dividers automatically. Various measurement routines have been developed for this purpose, which are described in detail in the system’s user manual.

Components

A Josephson voltage standard system consists of components specially developed by Supracon AG, as well as devices sourced from external manufacturers. The diagram illustrates these components along with their interconnections within the system. The Josephson voltage array manufactured in our cleanroom is cooled either with liquid helium or using a pulse tube cryocooler, also developed by Supracon AG. A dedicated compact bias source with an isolated power supply controls the PJVS array. In addition, our PJVS control electronics coordinate the multiplexer, cryocooler, and flip-chip heater for flux trapping removal, while also interfacing with sensors that monitor environmental conditions.

PJVS Bias Source

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PJVS Control Unit

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Power Supply

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Null detector

    Sampler

      Waveform generator

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