APPENDIX C. FORMULAS page 45
C. FORMULAS
The following formulas are used in various systems manufactured by TSA Systems, Ltd. They are provided to assist in verifying system operation and to give our customers a better understanding of how the systems operate
C.1. ACTIVITY FROM COUNTS
Where:
Activity = Activity in nCi
Eff = Decimal efficiency (i.e. 10% = 0.1.)
N = Net counts per second (cps – background cps)
C.2. EFFICIENCY
Where:
N = cps with source – background cps
activity = test source activity in nCi
C.3. N*SIGMA ALARM LEVEL
This formula calculates the minimum activity, in disintegrations per minute, that can be reliably detected under a given set of operational conditions.
Where:
bkg = Background counts
Sigma = 1bkg
N = N*Sigma value
Model
