Test and Measurement Forum

Hi,

Now that i've gotten the current monitoring kit to work, i tested it out on a 3-phase motor with the 3 current clamps provided. The 3 sensors gave slightly different readings. I am not quite sure about this, but i thought the 3 sensors should give the same readings for a 3-phase motor.

I would like to ask:
1) Does the close proximity of the wires and thus sensors affect the accuracy of the readings?
2) How will the sensitivity switch on the sensor (10mV/A, 1mV/A) affect the readings?

Best regards and thanks,
Y.H

Hi,
If the readings were always the same you would only need to monitor one phase. There can easily be variations. Put all the clamps on one phase to check if they all read the same. Errors should be minimal. Different positioning of the clamps on the wire will have a small effect. The x1/x10 switch will increase the reading by a factor of 10, It is there to enable better monitoring of low currents (below 30A).
Regards,
PeterF.

Hi PeterF,

Thanks for the reply.

It is written in the manual that the maximum allowable current is 300A. Does this mean that the sensor is more suited for high current measurements as the percentage error would be lesser?

Regards,
Y.H

Hi,
The maximum rated current for the current clamp is 300A. The x10 setting gives 3000mV output at 300A, instead of the normal 300mV. The EL040 converter accepts up to 1000mV and scales 1mV = 1A at all times. The EL040 can thus be used with 1000A clamps. On the x10 setting, the standard 300A clamps can be used up to 100A but they will read high by a factor of ten. Best Accuracy for the EL040 is:-
±1% (0 to 200 mV)
±2.5% (200 mV to 1 V)
Hope that helps.
Regards,
PeterF.

Thanks for the help, i have a better understanding now.