Nor-Cal CDG 160 OP Lit - Manual (Page 23)

CDG160-OP-LIT (2010-06) 23
4.2 Zeroing the Gauge
The gauge is factory calibrated while "standing upright"
(
→ "Calibration Test Report").
We recommend performing a zero adjustment, when the
gauge is operated for the first time.
Due to long time operation or contamination, a zero drift could
occur and zero adjustment may become necessary.
For adjusting the zero, operate the gauge under the same con-
stant ambient conditions and in the same mounting orientation
as normally.
The output signal (measuring signal) is depending on the moun-
ting orientation. The signal difference between the vertical and
horizontal mounting orientation is:
F.S. ∆ U / 90°
1000 Torr
≈2 mV
100 Torr
≈10 mV
10 Torr
≈50 mV
1 Torr
≈300 mV
If the gauge is operated via a controller, the zero of the
whole measuring system has to be adjusted on the
controller: first, adjust the zero of the gauge and then,
the zero of the controller.
4.2.1
<ZERO> Adjustment
The zero can be adjusted via
• the button on the gauge,
• the digital input "Remote Zero" (briefly apply the
supply voltage (+21 … +30 V) to pin 10),
• the RS232C interface (→  [1]),
• a Nor-Cal Vacuum Gauge Controller.
While the gauge is being heated and/or under atmos-
pheric pressure, the zeroing function is locked in order
for operating errors to be prevented.