I was read that it has two tubes- one designed for measuring lower levels, and the other for measuring higher levels- like those that would be encountered in an industrial environment. If that is the case, I want put it into the more sensitive mode for measuring lower levels.
Those two tubes have different sensitivity but use same high voltage source. Increasing the voltage may increase the sensitivity but will reduce the tube lifespan. There is a potentiometer on the board which can be adjusted to change the voltage of the tubes.
The software is not able to do that. The only way is to remove one of the tubes to independently use only one of them. The CPM is sill true from the tube but the usv/h and mr/h need to be calibrated. The low sensitivity tube cannot detect low level radiation and the resolution is going to be bad. Also if you remove the low sensitivity tube, the cpm will be the same as a GMC-500 unit but the usv/h and mr/h need to be calibrated.