Thyracont VCP63MA4, Руководство по эксплуатации

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VCP63MA4-200508
4 Operation
4.1 General
Measurement Principle
The VCP63MA4 vacuum transducer has an internal Pirani sensor, which uses
the heat conduction of gases for measuring vacuum. A sensor filament is heated
to a certain temperature threshold in pulsed mode, the time needed for heating is
a measure for total gas pressure.
Output Signal
The output signal 4.0 - 20 mA of your VCP63MA4 has a logarithmic dependence
on pressure over the whole measurement range 5.0x10
-4
- 1000 mbar.
Conversion of voltage signal and pressure is done according to the following
formula:
Warm-Up Time
The signal output of VCP63MA4 is available immediately after the unit is
switched on. To take advantage of the maximum accuracy of the unit it is
appropriate to allow for stabilization time of 5 minutes, especially when extreme
pressure changes have occurred.
Accuracy
The unit is adjusted ex works in upright position and at 24V voltage supply.
Through contamination, ageing, extreme climatic conditions or different mounting
orientation the need for readjustment may arise. Accuracy is reduced in the
range above 10 mbar and below 10
-2
mbar.
Dependence On Gas Type
The output signal depends 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. For other gases the pressure display can be corrected
below 0.5 mbar when the VCP63MA4 is operated with a Thyracont display unit.
Correction factor (to be multiplied with the uncorrected pressure reading):
Ar
1,6 H2 0,57 Ne 1,4
CO 1,0 He 1,0 Kr 2,4
CO2 0,89 N2 1,0
I
out
[mA] = 16/7 x log (p[hPa]) + 92/7
p [hPa] = 10
( 7/16 x (Iout[mA] – 92/7) )