Adapting non-RPM current clamps
to RPM Power Recorders

Although it is always advised, there are times when it is not possible to use the current clamps supplied by Reliable Power Meters or their distributors. Below is a suggestion for an adapter for connecting to non-standard current clamps or detection circuits.

Note: The inputs are not isolated from the instrument ground. The input into the instrument must be floating so as to avoid ground loop currents.

 

Direct Connection to the Instrument

Pin 4 - Signal
Pin 2 - Ground
Plug - 'Redel' part number PAA.M0.6GL.AC52G

 

Connection to the Instrument via the '3570' Current Lead

Pin 1 - Signal
Pin 2 - Ground
Socket - 'Redel' part number PRG.M0.4GL.LC52G

 

Operation

With this arrangement, the current is fixed at 5A Full Scale Deflection, and requires 2V to reach FSD making the sensitivity 1mV/2.5mA. In order to correct this, a multiplier can be inserted in the multiplier options in the software located under the heading "Options / Multipliers".

A formula for calculating the multiplier for adapting non standard clamps is:

Afsd = clamp full scale amps
Vfsd = output voltage of clamp at above full scale amps
Ratio = Interfacing CT Ratio (e.g. 300:5 = 60). Use 1 if no interfacing CT

If there are any questions please ask.