Combination Meter Scales

A common inquiry that we receive is the use of our survey meters and scintillation detectors with combination meter scales. The combination meter dial (counts per minute [cpm] and mR/hr) was designed so that a GM detector could be read in cpm and mR/hr simultaneously.

Another benefit of the combination scale is the advantage of using multiple detectors with one survey meter. For example, one can survey with a GM detector and read a pure gamma field in mR/hr or switch to a scintillation detector and read in cpm. However, due to the sensitivity contrast in different types of detectors, an error occurs when the scintillation detector is read in mR/hr instead of µR/hr. This will result in an erroneous or improper reading. If readings are required to be done in µR/hr, special combination scales are available if required, although some modifications to the survey meter may be necessary.

To determine if you have the correct combination meter face dial for your survey meter and detector, the following conversion chart may be helpful. Please contact us if you have any questions.