Specific settings for using LEM PCM30P/SP2 current clamps to monitor movement in both directions

The LEM PCM30P/SP2 sensor is bi-directional giving a positive-current waveform when the points swing in one direction (N-R) and negative-current when swinging in the opposing direction (R-N)

The set-up for the sensor is:

Value at 4mA = -30 A

Value at 20mA = +30 A

Set-up of the captures differs slightly, as you need to use analogue triggers:

Note that the “Logged Channel” is always the same as the “trigger channels”

All Triggers need to be set up as “Level” triggers

In the first direction (N-R in this example) we are looking to capture a positive current waveform.

The start trigger is > +5 Amps

The end trigger is < +0.5 Amps

In the opposing direction (R-N in this example) we are looking to capture a negative current waveform.

The start trigger is < -5 Amps

The end trigger is > -0.5 Amps

Note the change in direction, and the change in polarity!

Remember to set a zero-threshold. This trims up your captures nicely prior to transmission to Centrix. Set this to 0.5A

Remember that the “capture group” of the N-R and R-N swing must match

The (very hastily drawn) graph below illustrates what is going on here.

The SA380TX is smart enough to realise that when a negative capture is acquired that it should be flipped and sent to Centrix as a positive-shaped waveform.