SANAS CAL 043-01-00 · accredited since 1995
Where the industry sends its meters to be measured.
Other meter manufacturers send their instruments to our laboratory. Utilities bring us meters when a tampering investigation is heading for court. We have held SANAS accreditation to ISO/IEC 17025 since 1995 — for thirty years, through eighteen re-assessments of scope.
±0.03%
Measurement uncertainty
At unity power factor, k = 2
1995
Accredited since
Scope now at issue 18
17025
ISO/IEC 17025:2017
Testing & calibration competence
On site
Accredited in the field
Not only in the laboratory
Test uncertainty ratio
A calibration is only worth the instrument that performed it.
Measuring a meter with a reference barely better than the meter tells you almost nothing — the uncertainty of the reference swamps the error you are trying to detect. Metrology convention asks for a reference at least four times more accurate than the device under test.
Our accredited uncertainty is ±0.03% of measured energy. Against the meters that actually come through the laboratory, that is comfortably past the convention — and against a Class 1 revenue meter it is not close.
| 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 |
Our competitors' meters are calibrated here.
A substantial part of the laboratory's work is calibrating meters for other meter manufacturers — frequently Class 0.2 reference instruments, the most demanding devices we see.
We mention it because it is not something a company can say about itself. When the businesses PMT competes with choose this laboratory to certify their own accuracy, that is a judgement they made, not a claim we made.
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 – 100 A | 60 V – 250 V | ±3×10⁻⁴ · E @ 1 PF |
| 7.1.3 a | Three-phase energy meter — active | 0.01 A – 100 A | 50 V – 500 V | ±3×10⁻⁴ · E @ 1 PF |
| 7.1.3 b | Three-phase energy meter — reactive | 0.01 A – 100 A | 50 V – 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).
Some meters cannot come to the laboratory.
A CT-metered intake at a substation, a bulk supply point feeding a shopping centre, an 11 kV installation on a mine — these cannot practically be removed, transported and returned. Taking them out of service to prove their accuracy is often more disruptive than whatever prompted the question.
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
When the result has to 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.
It is a different discipline from metrology — evidential handling is its own competence — and 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-nineties PMT designed and supplied meter test equipment — the amplifiers, the reference standard and the software to adjust and calibrate meters — first to South African municipalities and Eskom, then into Malaysia, Zimbabwe, Swaziland and Australia. It was the company's core business for the better part of two decades.
We stopped around 2015, when the market had saturated. But it shapes how this laboratory works: we spent twenty years building the instruments other people calibrate on, and that is a different kind of understanding from simply owning a test bench.
An unbroken chain to the national standard.
Accreditation is only meaningful if the reference itself is anchored. 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 mutual recognition arrangement, so a certificate issued under CAL 043-01-00 is recognised internationally — it means the same thing in Midrand, in a billing dispute, and in a courtroom.
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