Berthold LB 134 - 9 Basis of Calculation; Calculating the Count Rate

LB 134 9. Basis of Calculation
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9. Basis of Calculation
9.1 Calculating the Count Rate
The LB 134 updates the calculation of the raw data in CPS
(counts per second) every second, i.e. the further calculation is
based on 1 second intervals.
General Formulas and Terms
t
Measuring time:
c
T
Time constant of the ratemeter [s]

Relative statistical error in %
I
T
Length of an interval (always 1s)
i
n
Counting pulses of the current interval
I
i
T
n
R 
Count rate (raw data) in actual second
R
b
Gross count rate (mean raw data)
R
b-1
Gross count rate of the preceding interval
n
R
Net count rate
0
R
Background count rate
0
T
Background measuring time
The gross count rate in the ratemeter mode is calculated using
an exponential weighting according to the formula:
1
*)1(*


bb
RWRWR
The weighing factor W is determined as follows:
W =
t
1
After the start of measurement, t starts at 1 and is incremented
by 1 every second, until the value of the time constant
c
T
has
been reached and then remains at that level.
In the Counter/Timer measurement (see below), the time con-
stant corresponds to measuring time after which the measure-
ment is terminated.
The number of seconds used for averaging is determined de-
pending on the measurement mode and can thus determine
whether a high degree of accuracy with slower response time to
activity changes, or a quick adaptation to changes associated
with a lower accuracy is obtained.