# Accuracy calculation of clamp-on power meters

## QFor 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.

A

The following example is based on the using the 3169 Clamp On Power HiTester 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."
* 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].