Sigma BM-286A service manual Reliable Detectable Activity RDA Formula

APPENDIX C. FORMULAS page 46

C.4. RELIABLE DETECTABLE ACTIVITY (RDA) FORMULA

This formula calculates the minimum activity, in disintegrations per minute, that can be reliably detected under a given set of operational conditions.

BKG = total background counts per count time

CON = confidence sigma

CT = count time in seconds

E = system efficiency in percent

F = false alarm level in cps

FA = false alarm sigma

G = intermediate variance

RDA = reliable detectable activity in DPM

C.5. SIGNAL TO BACKGROUND RATIO

The following formula is helpful is determining the optimum discriminator settings. Always perform a variance test at the final setting of the lower-level discriminator to ensure that system noise is not being introduced into the amplifier stage.

Where:

Q = Quality factor

S = Net signal (count with source - background)

B = Background count

B = Background count

Higher values of Q result in better sensitivity

Model BM-286A