Alexei, TVo

When we did the OMC scan while varying the SR3 RoC power, we noticed that the power monitor which is the digital product of an analog voltage and current monitor (found here) would have very odd behavior.  When we would request between 0.0 and 0.8 Watts, the current and voltage monitors would respond with the correct values we would expect from the simple equations (P=V^2/R=I^2*R).  However, when requesting above .8 Watts, the voltage monitor would rail and we'd get some nonsensical values.  We double checked that our drive calibration was correct in analog land, and everything turned out as we'd expect.  

We narrowed the problem down to what I think is a design issue, the voltage monitor when requesting say 0.8 Watts reads 9.7 Volts (positive-negative) at the input of the ADC.  The EL3104 modules only has a range of +/-10 Volts which means than any higher requested power will rail the ADC and gives back a nonsensical voltage reading.  I'm not sure how Beckhoff likes to throw and error if this is true. If I'm correct, we need to either switch to an ADC with a larger voltage range or an analog filter that attenuates the input signal so that we can get the full range of what we expect when energizing the heater.