Well, I may well have answered my own question: a 10K resistor between the counter out and the arduino in seems to resolve my issue.
Next question: how was the relationship between counts and exposure determined? We don’t know the energy of the particles we’re counting, which Q factor is most useful to the user, etc. I see widely varied ratios used for equipment sold on the net - and most of them provide no justification or basis for those numbers. An old surplus counter I have (non-working) has shutters of various material that shield against specific particles, so the user can make qualified assumptions about exposure…
Side note: I’ve made some corrections, and modified the code to work with serial LCDs, if anyone is interested. A work in progress…
All input welcomed!
Thanks -
Kevin