Chapter 3 Parameters
Mini-Switch LB 471
Leave the time constant on automatic unless there are good rea-
sons for entering a fixed value.
If you enter a fixed value as time constant, you should keep in
mind that a fixed value does not adjust to the source decay.
Therefore, enter a value that ensures a safe switching function
even after 10 years.
Rule of thumb: automatically calculated time constant x 10.
If the container is under high gas pressure or if significant wall
caking is to be expected, then it is absolutely essential that you
enter a fixed value. The value should be so great that possible gas
density variations or wall caking cannot trigger the alarm.
Rule of thumb: automatically calculated time constant x 30.
Live count rate (cps)
Display of non-average count rate.
(Only in the professional mode)
The displayed count rate comes directly from the detector and is
not averaged by the time constant.
Maximum time constant (s)
Upper limit of time constant in code 12
(Only in the professional mode)
If the time constant in code 12 is set to automatic, then the time
constant in code 12 is automatically increased or adapted to the
source decay, so that no false alarm can be triggered by statistical
fluctuations. To avoid that the time constant may become too big
over the years, you can here enter a value that triggers an alarm
as soon as the time constant in code 12 exceeds this value. The
display shows the error message 39.01 "Replace source". Code 55
shows the year in which the message is likely to be output.
Please keep in mind: If a fixed value has been entered in code 55,
then the error message "Replace source" is displayed as soon as
this date is exceeded. Code 14 is then disabled.
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