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5.8 Sensor Parameters
Gas Correction Factor (C1)
The measurement signal of the VSP/VCP depends on type and composition of the
gas being measured. The unit is adjusted for N
2
and dry air. For other gases the
pressure display can be corrected below 0.1 mbar by setting a correction factor.
The measurement results of the sensor are then multiplied with the correction fac-
tor by the unit’s microcontroller, thereby providing a corrected pressure reading as
analog and digital output.
Value range: 0.20 ... 8.0
Correction factor C1 Pirani:
Ar CO CO
2
H
2
He N
2
Ne Kr
1.6 1.0 0.89 0.57 1.0 1.0 1.4 2.4
Scaling of Output - Analog Output Characteristic (OC)
The analog output characteristic can be scaled according to application require-
ments by adjusting this parameter via software command. The voltage output cur-
ve can, for example, be modified to become compatible with transducers of other
brand labels.
A very comfortable way of scaling the output curve with graphical support is offe-
red by the VacuGraph
TM
software.
The data section of the software telegram contains the following parameters:
CHAR: »Log«: logarithmic relation between voltage and pressure
V
out
[V] = GAIN[V] x log (p[mbar]) + OFFSET[V]
»Lin«: linear relation between voltage and pressure
V
out
[V] = GAIN[V/mbar] x p[mbar] + OFFSET[V]
GAIN: G[float] gain in V per pressure decade or V per mbar
OFFSET: O[float] voltage offset in V
LOW.L: L[float] smallest admissible output voltage in V
UPP.L: L[float] highest admissible output voltage in V
UNDER.: U[float] voltage output in V in case of pressure underrange
OVER.: O[float] voltage output in V in case of pressure overrange
FAULT: F[float] error signal in V
VSP/VCP-RS485-200116
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