I really have no idea what I'm doing but if you could tell me what is the best way to setup my GMC-300E ....such as mR/h or uSv/h .....what do you prefer? Any insight would be great. Thanks ....Mike.

We use CPM. If you can make sure your geiger counters output to NETC is CPM, that would be considered good data. Theres a good reason for using CPM. Dose rate is not accurate on a geiger counter other than for the same isotope that the unit was calibrated for, which is likely cesium 137. The big problem is that the GMC-300E like other geiger counters pick up all different (beta & gamma) isotopes, it can not pick only one.

How do I set it for CPM?

Does the display on your geiger counter show that it is in CPM?

If not, what units does it display?

It now says "CPM" ....I did not know it could do that. Normaly it reads mR/h or uSv/h. I just kept pushing the button until it said "CPM". So I assume that is correct.

We utilize CPM. On the off chance that you can verify your geiger counters yield to NETC is CPM, that would be viewed as great information. Theres a decent explanation behind utilizing CPM. Measurements rate is not precise on a geiger counter other than for the same isotope that the unit was balanced for, which is likely cesium 137. The huge issue is that the GMC-300e like other geiger counters get all diverse (beta & gamma) isotopes, it can not pick one and only.