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Australian Government: National Measurement InstituteAustralian Government: National Measurement Institute
National Measurement Institute

Low Frequency Electrical and Magnetic Quantities Capabilities

Calibration services are available for voltage, ac-dc transfer standards, digital multimeters and calibrators, active and reactive power and energy meters and magnetics. Click here:

Before consigning an instrument for calibration always consult us to discuss your requirements. For further information contact


NMI's primary standard for voltage (or electric potential or electromotive force) is a Josephson junction array producing a dc voltage at the 10 V level.

Electronic Voltage References (EVR)

Electronic voltage references should have output voltage levels of 1 V, 1.018 V or 10 V. The instruments must have no externally accessible voltage adjustment and must be temperature-controlled by means of their own internal circuitry. Backup batteries should be fully charged before shipment and shipment should be arranged to avoid delays that result in discharge.

Standard Cells

Standard cells are highly likely to be affected by thermal or mechanical perturbations during transport. For that reason, NMI recommends the use of electronic voltage references in preference to standard cells and prefers not to accept standard cells for calibration. However when a client has only standard cells as a voltage reference, NMI may offer a calibration provided that prior arrangements are made. 

AC-DC Transfer Standards

A set of single junction thermal converters and micropotentiometers of NMI design serve as the primary standard for ac-dc transfer, providing traceability to the national standard for electric potential.

Clients' ac-dc transfer standards can be calibrated on voltage ranges from 2 mV to 1000 V at frequencies from 10 Hz to 1 MHz depending on the voltage range. Current ranges can be calibrated from 0.1 mA to 20 A at frequencies from 10 Hz to 100 kHz depending on the current range.

Ac-dc transfer tests on resistors can be carried out by arrangement with NMI at currents from 0.1 mA to 20 A and frequencies from 10 Hz to 100 kHz depending on the range.

Micropotentiometers can be calibrated on output voltage ranges from 1 mV to 300 mV at frequencies from 10 Hz to 1 MHz.

For information on calibration of ac-dc transfer standards for use at higher frequencies, see radio frequency and microwave calibration services.

Digital Multimeters and Calibrators

Digital multimeters displaying at least five full digits and equipped with an IEEE-488 bus interface may be tested on voltage, current and resistance ranges. If requested, NMI will adjust the instrument for minimum error. Tests on voltage and current calibrators, ac measurement standards and automatic ac-dc transfer instruments may be undertaken by arrangement with NMI.

Voltage tests can be made up to 1000 V on dc and ac at frequencies between 10 Hz and 1 MHz depending on voltage. Tests at lower frequencies may be undertaken by arrangement with NMI.

Current tests can be made at cardinal points between 100 µA and 1 A on dc and ac at frequencies between 50 Hz and 5 kHz.

Resistance tests can be made at cardinal points between 1 Ω and 1 GΩ.

Active and Reactive Power and Energy Meters

Australia's standards of power and energy are maintained using a thermal double bridge power comparator where ac power is measured directly in terms of dc quantities, which provides traceability to the standards for the dc volt and ohm. For power meter calibrations, power can be generated with an uncertainty of 50 ppm of apparent power. Energy meter calibrations are carried out by using time measurements directly linked to the Australian frequency standard together with the ac power standard.

Clients' reference standards of 0.05% accuracy or better may be tested on ac at mains frequency at all power factors with currents up to 150 A and voltages up to 600 V.


NMI undertakes the calibration of instruments for measuring magnetic fields as well as the measurement of magnetic properties of materials.

Samples for measurement could be submitted in the form of solids, powders or film. The optimum shape and size of samples depends on the particular measurement. In most cases solid samples are required to be in the form of rods, strips, annular rings or spheres.

Normal Induction and Hysteresis Loops in dc Magnetic Felds (using a dc permeameter)

Tests on Bars

Samples of circular section, 12.25 mm in diameter and not less than 250 mm in length, are preferred. NMI should be consulted before samples of other shapes and sizes are submitted.

Tests on Rings

NMI should be consulted for the preferred dimensions of rings before samples are submitted.

Magnetic Measurements on Small Samples (using a vibrating sample magnetometer)

Magnetic properties can be measured with this instrument in fields of up to 7.8 x 106 A/m. In general, samples should be in the form of small spheres between 3 mm and 6 mm in diameter but NMI can provide advice on the suitability of samples of other shapes and dimensions.

Magnetic Field Surveys

NMI may be able to perform magnetic field measurements (ac and dc) at the client's location.

Miscellaneous Magnetic Measurements

NMI may be able to perform tests additional to those described above. In particular, a SQUID magnetometer is available as a research tool for measurement of magnetisation over the temperature range 2 K to 800 K in a maximum field of 5.5 T.

Manufacture of Precision Electrical Measurement Equipment

NMI develops and manufactures unique measurement equipment to realise its electrical measurement standards and to provide high-accuracy calibration and testing services. This equipment is also available to the Australian industry and to national metrology institutes around the world.

  • PBA-1S Precision Buffer Amplier
    • I Budovsky, AM Gibbes and DC Arthur (1999) A high-frequency thermal power comparator. IEEE Trans. Instrum. Meas., 48(2), 427–430
    • I Budovsky and T Hagen (2010) A precision buffer amplifier for low-frequency metrology applications. in CPEM 2010 Digest, 28–29
  • Precision 1000 V Inductive Voltage Divide
    • GW Small, IF Budovsky, AM Gibbes, and JR Fiander (2005) Precision Three-Stage 1000 V/50 Hz Inductive Voltage Divider. IEEE Trans. Instrum. Meas., 54(2), 600–603
    • IF Budovsky, GW Small, AM Gibbes and JR Fiander (2004) Calibration of 1000V/ 50 Hz inductive voltage dividers and ratio transformers, in CPEM 2004 Digest, 322–323
    • HL Johnson, R Xie (2011) A young person's guide to Thompson's method for the precise measurement of voltage ratio, in Metrology Society of Australia Proceedings of the Ninth Biennial Conference, Melbourne, 93–100
  • Precision Multi-range Current Transformer
    • I Budovsky, T Hagen, F Emms,  HL Johnson, L Marais and V Balakrishnan (2014) Precision multi-range current transformer for the automation of electrical power standards, in Proc. CPEM 2014 Rio de Janeiro, 412–413
  • Precision Current Shunts
    • I Budovsky, AM Gibbes and DC Arthur (1999) A high-frequency thermal power comparator. IEEE Trans. Instrum. Meas., 48(2), 427–430
    • I Budovsky (2007) Measurement of Phase Angle Errors of Precision Current Shunts in the Frequency Range From 40 Hz to 200 kHz, IEEE Trans. Instrum. Meas., 56(2), 284–288
  • CCS-4S Computer Controlled Switch for AC-DC Transfer Measurement Systems