Inficon VGC083A - 7.9 CG1;CG2 NON-LIN Analog Output

tinb29e1-c (2019-10) VGC083A_B.om 59
When the analog output is setup, as described in section 6.5.6, for CG1 NON - LIN
or CG2 NON - LIN, the analog output voltage represents the pressure measured by
CG1 or CG2 for nitrogen/air only. Refer to section 8.3.3.3 if you are using a gas
other than nitrogen/air.
The first convection enhanced pirani head introduced was the Convectron
®
. The
controller for the Convectron® provided an analog output signal referred to as the
"S-curve" which represented the actual voltage applied across the head circuit,
proportional to the pressure inside the pressure head enclosure. The Granville-
Phillips
®
Convectron
®
controllers were designed to output this head voltage and in
later years, the non-linear voltage applied to the head was scaled to provide
various signal spans of the original "S-curve". The non-linear analog output of the
VGC083 duplicates the original S-curve of 0.375 volts at pressure less than
1.00 × 10
-4
Torr to 5.659 volts at 1000 Torr, nitrogen or air.
In general, one may use linear in-
terpolation techniques to calculate
the pressure using the non-linear
analog output voltage measured at
a specific pressure. You may also
calculate the N
2
/air pressure repre-
sented by the non-linear analog
output voltage for the original "S-
curve" using a multi-segment, n
th
order polynomial function calcula-
tion listed on the following page.
7.9 Analog Output for CG1
or CG2 NON - LIN
(Nitrogen / Air only)