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Meter: Test View
OMICRON´s approach significantly simplifies the testing of energy meters. Until now, the usual method has been to use a stabilized, but not very accurate, power source, in combination with a reference meter.
By using state of the art hardware technology, OMICRON provides test sets that are so accurate and stable, that the signal source itself represents the reference (applies especially to the extended precision (EP) option of CMC 156, CMC 256 and CMC 256plus test sets). This makes a reference meter unnecessary for most cases. The CMC test sets not only provide the test signals, but also have inputs for the meter pulses allowing closed loop testing. To this end, optical scanning heads for capturing pulses emitted by infrared LEDs are available.
Meter allows for manual or automated testing of energy meters. The automatic test is controlled by a test point table.
Load test | Accuracy of the measurement unit (time power method) |
Mechanism test | Accuracy of the entire meter incl. display |
Gated Mechanism test | Testing internal meter registers |
Injection test | Quick check (wiring, sense of rotation) |
No-load test | No start-up at zero load |
Creep test | Start-up at low loads |
Meter: Detail View
In the columns of the table the individual test parameters, the set assessment criteria (tolerance, nominal behavior), and the result of the test, including the assessment (passed or failed), are displayed. For multifunctional meters, or meters with two directions of rotation, a table per test function is available (multiple tabs). Test lines can be repeated several times. In this case the standard deviation is displayed together with the meter error, which allows conclusions of the correctness of the test itself. Single test steps (e.g. those assessed as failed) can be repeated after a test run is finished, without the need for repeating the whole test.
For testing the meter’s behavior with harmonics or DC components, the following current signal waveforms are available:
- Sine
- Sine + Harmonics
- Sine + DC
The test quantities are displayed graphically by means of the voltage, current and power vector diagrams on the right of the screen.The test can by performed with any balanced or unbalanced load for:
- Single phase meters (or a single measurement element of a 3-phase meter)
- 3-wire meters
- 4-wire meters
All parameters can be specified in a detail view independently for each phase. Apparent, active and reactive power is indicated for each phase and the whole rotary system. Testing of the following meter functions is supported:
- Wh importing /exporting
- varh importing /exporting
- VAh
- I2h and U2h (load/no-load losses of transformers)
- Qh (Quantity hour)
The results of an automatic test are clearly summed up in a tabular test report (one line per test point).
For a manual test, generating any test quantities, without defining a complete test procedure, can quickly check the correct functioning of meters. In this mode the constant of a meter can also be determined, in case it is not known or if there are doubts about it.
When testing with a reference meter, the CMC is used as a current and voltage source. During a load test the pulses of the meter under test, as well as those of the reference meter are registered. The latter form the reference for error calculation.
Furthermore, testing against a 0.02 or 0.01 % reference before a test is run, using the same test points, can eliminate errors of the CMC.