SENSseries LB 480 Level measurement
BERTHOLD TECHNOLOGIES GmbH & Co. KG
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Volume 3 7 Explanations
3
7.6 Time Constant
The time constant smoothes the output signal. Statistical fluctua-
tions, as well as level fluctuations due to the process, e.g. by agita-
tors, are smoothed.
The measured data supplied by the detector is averaged with the
time constant.
A so-called RC-averaging is carried out:
nM = aM + ((AZR - aM) * (1 - e(-t/
)
nM = new mean value
aM = old mean value
AZR = current, non-averaged count rate
(current display count rate)
t = time interval between the measurements in seconds
= time constant in seconds
Fig. 7-12 shows the reaction of the output signal in case of erratic
filling of the container (input change) from 0 to 100%.
Fig. 7-12 Time constant
Input change
Output signal
100%
64%
0%
Signal height
1
2
3
t
1 x = time constant, standard: 20s
3 x = virtually corresponds to the end value
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