Accuracy calculation of clamp-on power meters

Accuracy calculation of clamp-on power meters

Question

For current and power accuracy, the specifications indicate that clamp-on sensor accuracy must be added to the power meter's accuracy. Please advise how to calculate this in detail.

Answer

The following example is based on the using the 3169 Clamp On Poweter Meter with the 9661 Clamp Sensor (rated 500A).
The 3169's current and power accuracy is specified as "±0.2%rdg.±0.1%f.s.", and the 9661's current accuracy is specified as "±0.3%rdg.±0.01%f.s."
   * rdg. = reading error
   * f.s. = full scale error

By adding the 9661's accuracy to the 3169's accuracy, the total accuracy will become "±0.5%rdg.±0.11%f.s.".
Please note that the f.s. (full scale) is the current range of the 3169.



Current Measurement
(Example) 3169 with 9661
The clamp-on sensor's full scale error is calculated by "rated current/3169 range*0.01%".
As sch, the error will be 0.05%f.s. when using it in the 100A range. (= 500/100*0.01%).
When measuring 50.00[A] in 100A range on the 3169, the total accuracy will be "±0.5%rdg.±0.15%f.s.".
= ±(0.5% * 50.00 + 0.15% * 100)
= ±0.4 [A]
So, the actual measured value is between 49.6[A] and 50.40[A].


Power Measurement
(Example) 3-phase power measured by the 3169 with 9661
Current range:  10A / Power range:  6kW, Power factor = 1
When measuring 1.0000[kW] in the 6kW range, the error is calculated as shown below.
±(0.5%rdg. + 0.6%f.s.)
= ± (0.5% * 1.0000 + 0.6% * 6)
= ±0.041 [kW]
So, the actual value exists between 0.9590[kW] and 1.0410[kW].