Excellent question.

A/KIT1/A3 compute CPM counting all pulses during every minute. Then they send the data online.

Assuming the radiation field would be above the background level, you would sense the source if the one-minute average would also be above the background level. But keep in mind the inverse square law, which leaves little detection space if your speed increases distance from source very quickly.

I’ll write it down in an equation if I find the time.