How to Set EDTM Frequency with the DVCS Pulser
The EDTM (electronic dead-time monitor) is controlled via a DVCS pulser in the bbhodo crate. This pulser creates a pulse, normally 20 Hz, that is injected into the trigger decision logic of BB and HCal coming from their summing modules. This will create a signal that looks like a real trigger, however there will be no useful data associated as the trigger is simply from a pulser. To distinguish these fake events in later analysis copies of the EDTM pulser are sent into F1TDCs of both BB and HCal. So, if an event in either detector has signal in the F1TDC channel that contains a copy of the EDTM pulser we know that this was an EDTM event and not a real physics trigger. We can then find the electronics dead-time, coupled with the DAQ dead-time still, by comparing the number of EDTM events BB and HCal saw versus the number of EDTM pulses in a scaler.