Metrel newsletter

Metrel PQA: A 1756 Photo-scanning head

We are happy to announce a new accessory for selected power quality analysers that greatly enhances their versatility. The A 1756 Photo-scanning head enables measuring accuracy of mechanical and electronic electricity (energy) meters in conjunction with a new feature called “E-Meter” that became available with the new firmware (announced in one of previous newsletters).

The E-Meter feature compares data obtained with the A 1756 Photo-scanning head, which captures LED pulses from electronic meters or the number of disc turns in mechanical meters, and selected current clamps (measuring the same current that goes through the meter), like the A 1588 Current clamp 0.5/5/50 A / 1 V, and calculates discrepancies. It should be noted that the selection of current clamps greatly affects the reliability and accuracy (at best in the ballpark of 1 %) of analysis, which should therefore, even when the best clamps are used, be considered informative.

The E-Meter feature supports analysis of accuracy of active (Wh) and reactive energy (varh) measurements, and the user can even switch between the fundamental and IEEE 1459 calculation method for the reactive energy. As mentioned before, the E-Meter compares reference measurements obtained with current clamps, captured in 200 ms intervals, and those from the analysed electricity meter. Advanced algorithms then compensate for time lag occurring at the start and the end of the analysis, ensuring that the right signals from both sources are compared.

How the E-Meter functions compensates for time lag when comparing signals from current clamps and the A 1756 Photo-scanning head: