Berthold LB 134 - Ratemeter Function

LB 134 9. Basis of Calculation
117
9.2 Ratemeter Function
The weighting factor W described in chapter 9.1 can be deter-
mined either as a function of the time constant or the accuracy:
a) Preset time constant:
The number of seconds entered indicates the maximum time
constant that is used for averaging, which means that at a set
time constant of 100 s, the weighting factor is calculated with
W=1/100 after 100 s. In this case, the accuracy that can be
reached is dependent on the count rate and the time constant.
b) Preset accuracy:
When a relative accuracy
100*
b
b
R
R
in percent is to be reached, t in the above formula must be re-
placed by








 1
*
1
*
2
1
2
b
c
R
T

Preset accuracy is recommended for higher count rates (100
cps and higher).
If the count rate changes statistically significant within a short
period, then t is reset to 1 again and thus the new measured
values are again given more weight.
The reject criterion can be adjusted individually. For this pur-
pose, the standard deviation
I
b
T
R
 
, with T
I
= 1 s
is used as a measure of the statistical accuracy. If the differ-
ence between the current measured value and the current av-
erage is greater than an adjustable number of standard devia-
tions, then the averaging starts again from the beginning and t
is reset to 1. For the ratemeter, the preset reject criterion is 4 .