Chapter 3 Parameters
Mini-Switch LB 471
Detector high voltage
Show or set current high voltage of the detector
(only FSK detectors)
The automatic HV-control keeps the detector free from drifts in
case of temperature fluctuations and ageing.
Enter a value between 500 and 1300 V to set the detector to man-
ual high voltage.
To ensure a reliable function of the measurement, the HV has to
be set to automatic.
If the count rate of a NaI detector drops below 100 counts, the HV
is frozen. If it rises again above 200 counts, the HV is again con-
trolled automatically.
HV start value
Set start value of high voltage control
(only FSK detector)
A HV start value fulfills the following tasks:
Default value
After turning on power, the HV starts with this value. The
measurement will be ready for operation quickly.
Limit value for the HV control range.
It limits the HV control range of the detector to max. +40%
and min. 20% of the HV start value. A HV that is too high and
therefore detrimental to the photomultiplier cannot be generat-
ed. An error message is output if the HV touches one of the
cut-off regions (see page 71).
The start value is determined in the factory and stored in the de-
tector. If the photomultiplier has to be replaced, the automatic HV
value of code 53 automatically has to be entered in code 54.
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