Sensor CEM3 VAC Scaling and Regulation

Hi Andrew,

Essentially (when in regulated mode) the CEM3 has settings you can tweak for :
- Min scale - the voltage the dimmer outputs when it is at the threshold - usually 1% - so basically the minimum voltage it will output
- Max scale - the voltage the dimmer outputs when it is at full, at the output lug of the dimmer
- Scale load - when you load up a dimmer, some voltage is dropped internally, so the scale load tells the dimmer the proportion of the output load to the maximum load of the dimmer. In your case, a 575W lamp (4.79A) on a 20A dimmer means this should be set to about 23%

The dimmer has a calculation which is made based on the type of module and scale load in order to accurately hit the voltage at the output. Now of course, that's the voltage at the output of the dimmer, and more voltage will be lost through the cable to the load, again depending on the size of the load, the cross sectional area of the cable and the length of the cable.

I think you should :
1. Check your module types are set correctly, the D20 and TR20 have different chokes so the drop will be different, the CEM3 needs to know the right module type to calculate that
2. Check your scale load factor is correct - as mentioned above should be 20-23% for a 575W lamp on a 20A dimmer
3. Determine the voltage drop between your output and your load; probably easiest to measure to do that. Then you can adjust your max scale values by this much.

You can remotely alter all these settings in the rack using the Concert software; if you have a laptop, you can run the software remotely to allow you to tweak the voltage while measuring at the lamp end.

Hope that helps

-Tom

So this sort of works, and sort of doesn't.

I followed your suggestions above, changed the scale factor to 24, (via the concert software), confirmed it was set to the appropriate module (D20), etc. 

As I mentioned above, I have a sensor 96 touring rack. We use 16 mults from the rack to the lights. I chose a circuit, applied a Max scale VAC of 80V just to test, and tested both the multi output and the stage pin from the back of the rack. My results showed that the Stage Pin from the rack would read the correct Regulated voltage only when the pin patch for the multi circuit that is designated to that dimmer is unplugged.   It was spot on when the pin patch ports were all empty, and I metered the stage pin at the back of the rack.   When I re-ported the pin patch to the dimmer, it would return to 124v, or the input voltage of the rack.

At no time did the mult circuit read the regulated voltage.

Thoughts on this?

Remember that SCR dimmers need a load to have any regulation, otherwise they will float to full even when not driven. Could there be some kind of induced voltage from your multicables that is acting like a load enough to trick the dimmer? Are you patching empty dimmers?

Approximately 65 of the 96 dimmers have a 575w lamp on them. They were all sitting at around 50% except for the circuit I was testing which was at full. There were no empty dimmers patched. I suppose I could try again with all of the lights off except for the circuit I am metering, but if it was an induced voltage problem, why would it still read at 123v when the rest of the rig was at 50% (60v) and the max scale was also set to 60v? Would the induced voltage cause that much of an increase in the circuit?

Approximately 65 of the 96 dimmers have a 575w lamp on them. They were all sitting at around 50% except for the circuit I was testing which was at full. There were no empty dimmers patched. I suppose I could try again with all of the lights off except for the circuit I am metering, but if it was an induced voltage problem, why would it still read at 123v when the rest of the rig was at 50% (60v) and the max scale was also set to 60v? Would the induced voltage cause that much of an increase in the circuit?