The scalers are read out 10x per seconds, so they have an accuracy of 10 Hz. I tried a 50 Hz pulser, and measured 40 Hz, I tried 52 Hz and measured 50 Hz. This is about what you can expect.
The scaler rate is measured after the discriminator of the trigger, so the trigger level also affects the scaler reading. If you have a 100 mV pulse and your threshold is 200 mV, your scaler rate drops to zero. That can be seen best with the DRSOsc and sliding the trigger value. If you have a 50 Hz pulse with narrow (< us) pulses, things are fine. But if you use a 50 Hz square wave, then you get distorted signals due to the AC coupling which can also be confusing. See for example here: https://www.daqarta.com/dw_gg0o.htm
Hi. I'm trying to evaluate livetime of the evaluation board with the hardware scaler. I'm facing a strange issue.
I took the rate with the function, DRS->GetScaler(int channel).
I guess that channels 0--3 mean the rate for the channel, and channel 4 means the counter of the trigger.
I took the 1,000 pulses generated by a pulse generator with 50 Hz.
The scaler values are ~ 39.83, not 50.
The timestamp difference between the initial event and the final event is 19.98 seconds.
1000/19.98 ~ 50, thus, the evaluation board took the pulses with enough livetime.
Can we believe the scaler value for the livetime evaluation?