Thyracont VSH87D, Operating Instructions Manual

Page: 53 / 64

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To achieve optimum results of the adjustment we recommend to
consider a warm-up of at least 10 minutes at the appropriate cali-
bration pressure before any adjustment.
5.8 Sensor Parameters
Degas (DG)
Deposition or adsorbed gas molecules on the electrodes of the hot cathode sensor
may lead to increased degassing in ultrahigh vacuum or even cause instabilities of
the measurement signal.
In such cases it is appropriate to clean the anode of the sensor from such depo-
sited material and adsorbed gas molecules by degassing. This is done at pressu-
res below 2.0x10
-6
mbar by ohmic heating of the anode to temperatures around
800
◦
C.
The parameter is used to control the degas procedure and query the status.
»0«: Degas off
»1«: Degas on
The degas procedure will stop automatically after approx. 3 minu-
tes, but can be cancelled any time. While the sensor is degassing
the red status LED is flashing slowly in red color.
Degas Triggered by Voltage Signal - Degas Logic (DL)
Degas can be started simply by connecting pin 9 (see section 3.3.2) to a defined
voltage level for a short moment (min. 20 ms). With parameter »Degas Logic« (DL)
you can configure whether a 3 ... 24 VDC or GND signal shall be used:
»0«: GND, active low (default)
»1«: 3 ... 24 VDC, active high
Sensor Transition (ST)
By default the VSH performs a continuous transition between Pirani and hot ca-
thode range whereupon an assimilation of the sensor signals is carried out.
In order to adapt the performance of the transducer to the requirements of the
vacuum process the following options can be configured by means of parameter
»Sensor Transition« (ST):
VSH-RS485-200116