BERTHOLD TECHNOLOGIES LB4710-050, User Manual

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Chapter 5 Explanations
Mini-Switch LB 471
66
5.5
Time Constant
The time constant smoothes the measured value in code 10 and
11. Statistical fluctuations and process-immanent level variations,
e.g. due to agitators, can be smoothed.
The measured values supplied by the detector are averaged using
the time constant. A so-called RC-averaging is performed:
nM = aM + ((AZR – aM) * (1 – e(-t/
τ
)
nM = new average value
aM = old average value
AZR = current, non-averaged count rate
t
= time distance of measurements in seconds
τ
= time constant in seconds
Figure 15 shows the reaction of the percentage reading in code 10
if the container has not reached or has exceeded its monitoring
level. The reading in the instrument is averaged new every 0.5 s.
Figure 15:
Time constant
100%
0%
64%
1
τ
2
τ
3
τ
Input change
Output signal LB471
t
Si
gnal
hei
ght