The Electrical Metrology Laboratory involves in the development, maintenance and dissemination of measurement standards in the fields of electrical direct current (DC) and low frequency alternating current (AC) quantities that form the basis of Singapore electrical measurement traceability chains to the SI units. 

Our realisation and dissemination of the units of electrical measurement ensure that industries and other users have access to accurate and reliable measurements. We work in advancing measurement science, conducting R&D in measurement technology, evolving measurement capabilities, and providing measurement solutions to support industry’s technological innovation and competitiveness. Some of the key focus areas of the laboratory include:

Dissemination of Traceability & Metrology Expertise

  • Research and development for the realization and maintenance of electrical units
  • Precision calibration and measurement of electrical parameters direct traceable to national standards
  • Measurement uncertainty and reliability analyses
  • Design and verification of bespoke measurement systems
  • Metrology capability and competency development and consultancy

Metrology for Energy Grid

  • Energy efficiency and power system condition monitoring and analysis
  • Measurement of high voltage, electrostatic discharge detection and electrical breakdown

Metrology for Electrical Characterisation

  • Electrical measurement & characterisation of material properties, sensors and devices


  • A new high voltage system which extends NMC's capability in AC high voltage from 100 kV to 200 kV at an accuracy of 0.05%. It will provide measurement traceability to local industry in relevant measurements and tests. It will also be used to carry out high voltage withstanding tests for insulation material developments and aerospace apparatus designs.
  •  Resistance bridges are crucial for resistance thermometers measurements. Very often, the linearity of the resistance measurement range needs to be correctly accounted for to achieve a low measurement uncertainty. Using a resistance bridge calibrator, the ratio indicated by a resistance bridge can be validated to perform a check of the linearity of the resistance bridge. NMC is now providing the linearity validation for ac and dc resistance thermometry bridges to the industry.
  • NMC organised a proficiency test (PT) on resistance measurement using 100 Ω and 10 kΩ standard resistors starting from third quarter of 2018 to first quarter of 2019. The resistance values were typical PT100 (100 Ω PRT) and thermistor (10 k Ω) values that are typically used by temperature measurement for Green Mark M&V so that accredited laboratories, ESCO or building facility management companies can tap on the opportunity to verify their capability and instrumentation’s performance.


The ampere, symbol A, is the SI unit of electric current. It is defined by taking the fixed numerical value of the elementary charge e to be 1.602 176 634 x 10–19 when expressed in the unit C, which is equal to A s, where the second is defined in terms of ∆ⱱCs.

(∆ⱱCs : the caesium frequency.) 

The high accuracy realisation of the ampere directly in terms of its definitions is difficult and time consuming. The practical realizations of the ampere are now obtained through combinations of realizations of the volt, the unit of electromotive force, and ohm, the unit of resistance. The SI unit of volt and ohm are reproduced at NMC’s electrical metrology laboratory via Josephson and quantum Hall effects respectively to indirectly realise the ampere that is significantly more reproducible and stable than a few parts in 107.

The Quantised Hall Resistance Primary Standard

The primary resistance standard is derived from the quantum Hall effect. The quantum Hall effect is observed when a current-carrying semiconductor heterostructure device is placed perpendicular to a large magnetic field at a sufficiently low temperature. Under this experimental condition, for certain magnetic fields Bz, the quantized Hall resistance (QHR) RH became quantized and appears as plateaux at values that only depend on fundamental constants.


where the number i=1,2,3,4… denotes the resistance plateaux of R.

Services Provided:

  • Standard resistors.

The Josephson Junction Array Primary Voltage Standard

The volt V is realized using the Josephson effect and the following value of the Josephson constant KJ: 483 597.848 416 984 GHz V–1.

When a junction created by two superconductors separated by a thin insulating barrier of a few nanometer in thickness is irradiated with microwaves, a discrete voltage level V is generated between the superconductors depending only on the frequency f of the microwaves and the Josephson constant KJ.

The Josephson constant KJ = 2e/h is the ratio of two fundamental constants - the Planck’s constant h and elementary charge e. The number n=1,2,3,…. denotes the total number of the constant voltage steps.

The Josephson array voltage standard at the National Metrology Centre provides calibrations for voltage up to 10 V at typical expanded measurement uncertainties (k=2) for calibration of Zener voltage standard at 1.018 V and 10 V of 0.1 μV/V and 0.05 μV/V respectively.

Services Provided:

  • Zener voltage standard

Direct Voltage

The primary standard for dc voltage is derived from the Josephson effect.

Measurement system based on the Josephson array is used as absolute voltage reference for the calibration of dc voltage standards such as Zener voltage standards.

The Josephson array voltage standard calibrates voltage range from -10 V to +10 V. Typical expanded measurement uncertainties (k=2) for calibration of Zener voltage standard at 1.018 V and 10 V are 0.1 μV/V and 0.05 μV/V respectively.

The reference standard for dc voltage is maintained by periodic intercomparison of a group of 10 Zener references.

Zener references and voltage divider are used to transfer the 10 V standard into electrical multifunction calibrator which will then source any dc voltage from zero up to approximately 1100 V.

The voltage ratio of a resistive divider with equally dividers resistance chain that are used for scaling of the dc voltage is determined using the reference voltage source bootstrap method, an absolute calibration method in the form of a “self-calibration” arrangement.

Services Provided:

  • Voltage divider
  •  Voltage meter
  • Standard voltage source

Direct Current

A typical current measurement setup consists of a resistance standard or current shunt and a voltmeter to measure the voltage across the resistor or shunt.

NMC is able to calibrate dc current source and meter from 100 mA to 20 A at expanded measurement uncertainties (k=2) from 4 to 65 mA/A.

NMC has set up systems to calibrate small current measuring equipment based on high resistance shunt and charging capacitor techniques. Equipment such as Electrometer, high-resistance meter, sub-femto-ampere remote source meter, and picoammeter can now be calibrated in NMC in the range of 1 pA to 0.1 mA A at expanded measurement uncertainties (k=2) range from 300 to 5 μA/A.

Services Provided:

  • Standard current source
  • Dc current shunt
  • Low current meter
  • Low current source


The quantized Hall resistance is used as an absolute 12.906 4035 kΩ resistance reference and maintained by a bank of 100 Ω resistance standards. A dual SQUID cryogenic current comparator resistance bridge is used to calibrate resistance standards against the quantized Hall resistance standard at typical expanded measurement uncertainties (k=2) better than 0.1 μΩ/Ω.

Standard resistors and direct current comparator resistance bridges are used to transfer the unit of resistance to standard resistors from 0.1 mΩ to 1 TΩ. The scaling of resistance standard periodically verified by intercomparison of groups of 1 Ω and 10 kΩ standard resistors.

The range of resistance standards are used to calibrate multifunction calibrators or meters.

Services Provided:

  • Resistance standard
  • Resistivity meter


The capacitance standards in NMC are maintained by groups of capacitance standards. Standard capacitors are compared to the reference standards using capacitance bridges. Capacitor from 1 pF to 1 mF is calibrated with expanded measurement uncertainties (k = 2) from 1 to 60 mF/F.

The inductance standards in NMC are maintained by groups of inductance standards. Standard inductors are compared to the reference standards using impedance bridges. Inductor from 100 mH to 10 H is calibrated with expanded uncertainties (k = 2) from 150 to 340 mH/H.

Services Provided:

  • Capacitance meter
  • Capacitance standard
  • Inductance meter
  • Inductance standard
  • Impedance meter

AC-DC Difference

AC-DC transfer standards are used to establish traceability for AC voltage (current) to the DC voltage (current) based on equivalence in power dissipation of the applied AC and DC voltages (currents) by means of a transfer standard such as a thermal converter (TC).

Measurement systems are used to compare the AC-DC differences of TC and to scale the measurement for voltage and current up to 1000 V and 20 A respectively.

The AC-DC voltage and current difference values are used to derive the traceability of AC voltage and current for frequency range up to 1 MHz and 100 kHz respectively at best expanded measurement uncertainties (k = 2) better in a few parts in 106.

Services Provided:

  • AC-DC current transfer device
  • AC-DC voltage transfer device
  • Standard AC current source
  • Current shunt

AC Voltage and Current

The AC voltage and current standards are derived in NMC, by using AC-DC voltage and current transfer standards with known AC-DC difference values. This values are used for corrections when trace AC quantities to DC ones.

AC voltage from 2 mV to 1 kV, from 10 Hz to 1 MHz can be derived at expanded uncertainties (k = 2) ranged from 9 x 10-6 to 0.59 %. AC current, range from 0.2 mA to 10 A, from 10 Hz to 10 kHz can be derived at expanded uncertainties (k = 2) ranged from 40 to 400 x 10-6.

Services Provided:

  • AC voltage/current meter
  • Standard AC voltage/current source
  • AC Current Shunt

Power and Energy

The measurement traceability in electrical power is achieved by characterising and maintaining a group of standard watt converters with reference to AC voltage, AC current and phase standards, and frequency standard for electrical energy calibrations.

Digital sampling method is used to perform harmonics measurement for power quality characterization, calibration of power meter, power analyser, and energy meter under sinusoidal and non-sinusoidal conditions. This is to support electrical power metering, power quality evaluation and electronic energy meter's characterisation for power range up to 20 kW, at expanded measurement uncertainties (k = 2) from 40 to 900 μW/VA.

Besides, NMC also maintains standards for phase angle calibrations, at expanded measurement uncertainties (k = 2) from 4 to 50 m° for sinusoidal signals at 10 to 100 000 Hz.

Services Provided:

  • Power converter
  • Power calibration standard
  • Power analyser
  • Power meter
  • Energy meter
  • Phase standard
  • Phase meter

High Voltage

NMC’s high voltage laboratory has the capability for measuring high DC and AC voltages up to 200 kV respectively. Resistive dividers are used as reference standards for high DC voltage, with expanded measurement uncertainties (k = 2) between 30 to 70 μV/V. Standard voltage transformers and standard capacitance are used as reference standards for high AC voltage, with expanded measurement uncertainties (k = 2) of 0.06 %.

The high voltage capability supports high voltage tests and measurements in electrical power and energy related industries, but also dielectric characterization and insulation design for new product developments.

Services Provided:

  • High voltage divider
  • High voltage meter
  • High voltage generator
  • High voltage tester
  • Impulse tester
  • Electrostatic analyser
  • Electrostatic detector

Focal Point: Accuracy Evaluation of Power and Energy Meters

Electricity Metering

Accurate measurements of energy and power are essential for energy supply custody transfer billing from energy suppliers to the users, and for energy efficiency monitoring and evaluating to support schemes on energy sustainability.

Accuracy verification of Electricity Meter

Calibration of an electricity meter assures fair trading of electricity.   Standard power values are generated  at defined voltages, currents and power factors for calibrations of such meters. International standards such as IEC 62053-21/22 are referred to for proper operations and definitions of the accuracy of the units under test.

Power reference systems with best uncertainty better than 0.01 % in one-phase or poly-phase at voltage up to 1000 V and current up to 100 A. The frequency is normally 50 Hz but may be varied up to 400 Hz to suit different applications. Harmonics up to 99th can be imposed for simulating various real waveforms. 

Power Measurement for Green Mark

The laboratory is working with government agencies and the industry to support energy efficiency related measurements and verification. The laboratory provides electrical measurement validation, consultancy and knowledge transfer services on green building energy efficiency measurement and verification and smart grid condition monitoring applications to industry and research institutes.

Focal Point: Electrical Measurement Verification and Reliability Analysis

In response to the trend in safety and quality assurance to reduce the probability of false acceptance, as well as performance validation of prototype products, industry often require specialised expertise to ensure the measurements produce relevant, reliable and accurate results.

Some of the electrical measurement verification and characterisation work NMC carried out for the industry:

  • High voltage measurement system verification
  • Surface resistivity measurement for ESD controlled product
  • Characterization of stun devices
  • Aircraft battery charger/analyzer
  • Dry cell battery production testing systems
  • Welding current verification for oil and gas equipment company
  • Test station verification
  • Characterization of a passive network filter
  • Touch current simulation network verification
  • Impedance spectroscopy measurement of devices

Focal Point: Electrical Characterisation of Materials and Devices

Evaluation of Charge Characteristics on Dielectric Surfaces

Friction or rubbing on objects can easily induce surface charge. This accumulated charge may trigger sparks as effective ignition sources in explosive environments. It is important to investigate the charging characteristics to identify possible ignition source for explosion prevention. The NMC performs such investigations for various applications of dielectric materials, including those for use on marine off-shore platforms environment.

Evaluation of Dielectric Characteristics of Encapsulation Material

New power electronics devices can potentially operate with minimal cooling requirements at high temperatures. To develop this technology for more electrical aircraft, the limiting factors lie in the packaging and interconnections of the dice in power module.  The NMC supports R&D work in high temperature and high voltage encapsulation design and tests for such devices. We also evaluate the encapsulation’s performance and life span under harsh conditions.

Electrical Impedance Characterisation of Devices

DC parametric and impedance spectrum measurement systems for electrical characterisation of MEMS and semiconductor devices. The characterisation capabilities system includes DC electrical parameters measurement system for voltage-current, power and pulse measurement at low level signal, Low frequency impedance (L, C, R) measurement system for precision measurement impedance measurement up to 1 MHz, and high frequency impedance and frequency response analyser system for measurement up to 100 MHz. Measurement capabilities are also available for small signals and impedance spectroscopy characterisations of devices and materials.

Characterisation of Measuring Network such as body impedance network, perception and reaction network, let-go network as specified in IEC 60990 for measurement of touch current and protective current for safety evaluation of apparatus are done using equivalent circuit network. Leakage current and patient auxiliary currents network as specified by IEC60601 for medical electrical equipment, and resistivity measurement system is using equivalent circuit network to calibrate the 4-point surface.


training course

The Electrical Laboratory constantly provides public and customised trainings for professionals and managers on current and emerging technologies. These trainings also act as a platform to educate scientists and engineers working in the fields of electrical calibrations, tests and measurements, and of apparatus maintenance.

Courses conducted in the past:

  • Achieving traceability in electrical measurements
  • Digital Multimeters and their Calibrations
  • Uncertainty evaluation in electrical measurements
  • Using data logger for temperature monitoring
  • High voltage test techniques and safety measures 
  • Power measurement for energy efficiency monitoring.

International Comparisons

To ensure the international equivalence of CMCs, the NMC Electrical Laboratory actively participates comparison programs organised both by regional and international metrology organizations. It piloted APMP.EM- K12 Comparison of AC-DC current transfer standards, and organized a few bilateral comparisons with other national metrology institutes.

Recently participated international comparisons:

  • BIPM.EM- K10.a DC voltage, Josephson standards
  • BIPM.EM- K10.b DC voltage, Josephson standards
  • BIPM.EM- K11.b DC voltage, Zener diode
  • BIPM.EM- K12Quantum Hall resistance standards and their scaling to other resistance values
  • BIPM.EM- K13.a Comparison of resistance standards
  • BIPM.EM- K13.b Comparison of resistance standards
  • CCEM- K5 AC power at 50/60 Hz
  • CCEM- K11 AC/DC voltage transfer difference at low voltages
  • CCEM- K12 Comparison of AC-DC current transfer standards
  • APMP.EM- K12 Comparison of AC-DC current transfer standards
  • APMP.EM.BIPM- K11DC voltage, Zener diode
  • APMP.EM.BIPM- K11.2DC voltage, Zener diode
  • APMP.EM.BIPM- K11.3DC voltage, Zener diode
  • APMP.EM- K1Comparison of resistance standards
  • APMP.EM- K2Comparison of resistance standards
  • APMP.EM- K4Comparison of capacitors
  • APMP.EM- K4.1 Comparison of capacitors
  • APMP.EM- K5AC power at 50/60 Hz
  • APMP.EM- K5.1 AC power at 50 Hz/60 Hz
  • APMP.EM- K6.a Comparison of AC/DC voltage transfer standards
  • APMP.EM- K9 AC/DC transfer difference at higher voltage
  • APMP.EM- S1 Comparison of capacitors
  • APMP.EM- S2Comparison of AC/DC voltage transfer standards
  • APMP.EM- S3Comparison of DC high voltage resistive divider
  • APMP.EM- S7Comparison of capacitors
  • APMP.EM- S12Comparison of standards for the calibration of voltage, current and resistance meters

Research Projects


High Temperature Dielectric Material to Encapsulate High Voltage Power Semiconductor Devices

New wide band gap power semiconductor devices are fast emerging for modern applications, including electrical aircrafts. Their encapsulation materials constrain their applications. Existing encapsulation materials often exhibit poor thermal endurance above 170°C junction temperature, and failures of delamination and voids, which further cause partial discharge and breakdown in moisture barrier. Collaborated with IME and IMRE, NMC piloted a project and developed a novel encapsulation based on silicone resin as the dielectric, and with an extra dielectric coating. It suits encapsulations for 20 kV/mm and 250 °C at junctions and 1200 V at busbar.