SANAS CAL 043-01-00 · ISO/IEC 17025:2017
Accredited by SANAS since 1997. Calibrated to South Africa's standards.
PMT's laboratory has held SANAS accreditation to ISO/IEC 17025 since 1997. We calibrate energy meters to make sure they meet South Africa's metering standards. They include our own meters, reference instruments from other meter manufacturers, and meters that utilities bring to us when a tampering investigation is heading for court.
- SANAS accredited since
- 1997
- Measurement uncertainty
- ±0.03%
- At unity power factor, k = 2
- ISO/IEC 17025:2017
- 17025
- Testing & calibration competence
- Accredited in the field
- On site
- Not only in the laboratory
Measurement uncertainty
Every calibration states its uncertainty. Ours is ±0.03%.
A calibration result is two numbers: how far the meter is from the true value, and how sure we are of that figure. The second is the measurement uncertainty. SANAS assesses ours as part of our accreditation: ±0.03% of measured energy at unity power factor, at 95% confidence.
That figure is only worth something if the reference behind it can be traced, without a break, to the national measurement standards held by NMISA. Ours can.
SANS 474, the South African code of practice for electricity metering, requires every new or replacement three-phase, post-paid single-phase and smart meter to be individually calibrated by an accredited laboratory before it is installed. For a licensed distributor, compliance is a condition of its NERSA licence.
SANAS verifies the laboratory's competence, the laboratory keeps the calibration report, and the certificate goes to whoever is responsible for the installation. That is the work this laboratory is accredited to do.
| Device under test | Accuracy class | Ratio to ±0.03% |
|---|---|---|
| Reference meters, third-party manufacturers | Class 0.2 | 6.7 : 1 |
| MOL4000 | Class 0.5S | 17 : 1 |
| MTR series | Class 1 | 33 : 1 |
Metrology convention asks for a reference at least four times more accurate than the meter under test.
Our competitors' meters are calibrated here.
A substantial part of the laboratory's work is calibrating meters for other meter manufacturers, including companies that compete with PMT. These are frequently Class 0.2 reference instruments, the most demanding devices we calibrate.
Scope of accreditation
DC low frequency metrology: AC power and energy at 50 Hz, by direct comparison with a reference standard. This is the scope SANAS assesses, and it is a matter of public record.
| Item | Instrument | Current | Voltage | Uncertainty |
|---|---|---|---|---|
| 7.1.1 | Single-phase energy meter | 0.01 A to 100 A | 60 V to 250 V | ±3×10⁻⁴ · E @ 1 PF |
| 7.1.3 a | Three-phase energy meter, active | 0.01 A to 100 A | 50 V to 500 V | ±3×10⁻⁴ · E @ 1 PF |
| 7.1.3 b | Three-phase energy meter, reactive | 0.01 A to 100 A | 50 V to 500 V | ±3×10⁻⁴ · E @ 1 PF |
| 18 | On-site calibration for three-phase energy meters | |||
Uncertainty expressed at a coverage factor of k = 2, approximately 95% confidence. ±4×10⁻⁴ at 0.5 power factor (0.8 for reactive).
On-site calibration for meters that cannot be removed.
Some meters cannot practically be removed, transported and returned: for example a substation intake metered through CTs (current transformers), a bulk supply point feeding a shopping centre, or an 11 kV installation on a mine. Taking them out of service to prove their accuracy is often more disruptive than the concern that prompted the check.
Item 18 of our scope accredits us to calibrate three-phase energy meters on site, under the same accreditation and to the same uncertainty. The certificate carries the same weight as one issued in Midrand.
Forensic calibration
Results that must stand up in court.
Where a utility suspects a meter has been tampered with, the measurement becomes evidence. PMT performs forensic calibration for utilities investigating tampering, in the presence of the utility's representatives and the investigating authorities.
We take formal custody of the instrument and maintain the chain of custody in accordance with legal requirements, with the documentation that a prosecution requires. Cases we examine frequently proceed to court.
Evidential handling is a different discipline from metrology, with its own competence. It is the most demanding test of whether a laboratory's results can be relied upon.
For twenty years we built the equipment other laboratories calibrated on.
From the mid-1990s, PMT designed and manufactured electricity meter test equipment, including power amplifiers, reference standards and the software used to test, adjust and calibrate meters. Initially supplied to South African municipalities and Eskom, PMT equipment was later exported to Malaysia, Zimbabwe, Swaziland and Australia. Meter test equipment remained a core part of our business for almost two decades.
While we no longer manufacture test equipment in-house, we continue to supply calibration equipment and expertise. Most recently, PMT supplied equipment to Ghana as part of the development of national electricity meter calibration capacity.
That history still shapes the way our laboratory operates. For twenty years, we built the instruments and systems that others used to calibrate electricity meters. It gave us an understanding of metering accuracy, measurement uncertainty and calibration that goes well beyond simply operating a test bench.
An unbroken chain to the national standard.
Accreditation depends on the laboratory's reference standards being traceable. PMT's reference standards are traceable to the national measurement standards maintained by NMISA, the National Metrology Institute of South Africa.
SANAS is a signatory to the ILAC (International Laboratory Accreditation Cooperation) mutual recognition arrangement, so a certificate issued under CAL 043-01-00 is recognised internationally. It carries the same standing in a billing dispute or in court.
- 01
Your meter
The instrument under test
- 02
PMT reference standards
±0.03% · CAL 043-01-00
- 03
NMISA
National measurement standards
- 04
SI
The international system of units