Ludlum Measurements 334A, Operation Manual

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Model 334A Operations Manual
Ludlum Measurements, Inc 38 January 2021
Uncertainties in Flow Rate
The measurement of the flow rate and volume has a statistical variance that contributes to the
MDC and MDD. This statistical variance is calculated by the program and applied in the MDC
and MDD calculations.
Calculation of the Variance of Peak Counts
The variances returned from the curve fit routine represent the uncertainties on the peak counts
for each isotope during the last peak-fitting. The limit of detectability variance used is a
combination of the fit variance with the previously saved ‘zero-counts’ variance.
 
2
0
645 . 1 Variance VarZero K Var
LD
 
Where, K is the Sigma Factor—a multiplier based on the False Alarm setting and the number of
alarm determinations per year.
Calculation of the Minimum Detectable Activity - MDA
Eff Cal T
Var
MDA
W A
LD
 

Calculation of the Minimum Detectable Concentration - MDC
 
DAC
VOL
W A
W A
LD
K
ion Concentrat
Volume
Error
Net
T
Net Net
Variance
T
Variance Var
MDC




















 

 


2
2
0
0 1
0
0


Calculation of Minimum Detectable Dose - MDD
DAC Sample
Flow
K
Dose
Flow
Error
Activity
MDA
MDD

















2
2
Where,
Variance
0
= Peak area variance for previous
W A
T
Variance
1
= Peak area variance for most recent
W A
T