Thyracont VD84M, Operating Instructions Manual

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25
Further model VD84MIR with infrared data-interface can
-
transmit measurement data directly to a PC (online-transmission) or
-
store measurement data in the instrument (datalogging) and via push of a
button transmit them to a PC afterwards
Measurement Principle
The VD84 compact-vacuummeter is connected to an external Pirani sensor,
which uses the heat conduction of gases for measuring vacuum. In a bridge
curcuit the filament is heated to constant temperature, the neccessary bridge
voltage is a measure for total gas pressure.
Warm-up-time
Pressure is displayed immediately after the unit is switched on. To take
advantage of the maximum accuracy of the unit it can be appropriate to allow for
stabilization time of 2 minutes, especially when extreme pressure changes have
occured.
Accuracy
The unit is factory adjusted. Through contamination, ageing or extreme climatic
conditions the need for readjustment may arise. Accuracy is reduced in the range
above 20mbar and below 10
-2
mbar.
After a new sensor head is connected we recommend to readjust the unit in
order to have maximum accuracy.
Dependency on gas type
The Pirani measurement is depending on composition and type of the gas being
measured. The unit is adjusted for N
2
and dry air. With He and CO deviations will
be almost negligible below 0,5mbar.
Proper Use
The VD84 serves exclusively to provide total pressure measurements in the
range 100 – 0.001 mbar. It may only be connected to components specifically
provided for such purpose.
Improper Use
The use for purposes not covered above is regarded as improper, in particular:
-
the connection to components not allowed for in their operating instructions
-
the connection to components containing touchable, voltage carrying parts.
No liability or warranty will be accepted for claims arising from improper use.
The user bears the responsibility with respect to the used process media.