Granville-Phillips Series 330, Инструкция по эксплуатации, Страница: 54 / 76

5 Convectron Gauge Module
54
Series 330 Vacuum Gauge Controller
Instruction Manual - 330004 - Rev. 02
5.3.6 Gauge Zero and Atmospheric Pressure Adjustments
Each Convectron gauge is individually computer-calibrated for N
2
. Adjustment of the zero should
not be necessary unless readout accuracy is required below 1 x 10
–3
Torr. Adjustment of the
atmospheric indication should not be necessary unless compensating for long cables or variations
in mounting orientation. The Convectron gauge has a stable, temperature compensated design and
each Controller is also calibrated to provide accurate readout of N
2
pressure with any gauge when
properly installed with the gauge axis horizontal.
1. Evacuate Convectron gauge A to a pressure known to be less than 1 x 10
–4
Torr.
2. With power ON and at vacuum less than 1 x 10
–4
Torr for at least 15 minutes, adjust the VAC
for gauge A until the analog output indicates an analog output voltage corresponding to
1 x 10
-4
Torr.
3. Let the pressure in the gauge increase to the local atmospheric pressure.
4. Read the local atmospheric pressure on a nearby, accurate barometer.
5. With power ON, adjust the ATM until the analog output indicates the local atmospheric
pressure in the pressure units you have selected.
6. NOTE: 1 atmosphere at sea level is 7.6 x 10
+2
Torr; 1.0 x 10
+3
mbar; 1.0 x 10
+5
pascal.
7. Repeat this procedure for Convectron Gauge B, if used.
The voltage signal is smooth and continuous throughout all the decades of pressure measurement.
This format is useful for computerized data acquisition because a simple equation (finding the
common antilogarithm) may be programmed to calculate pressure from the voltage output.
The equation is: P
i
= 10
V–4
Torr/mbar, or P
i
= 10
V–2
pascal
If the offset has been adjusted to other than 0V at 10
–4
Torr, then the exponent value must be forced
to –4 when the pressure is at 1.0 x 10
–4
Torr.
For example, if the offset has been adjusted so that the output voltage is –7 V at 1 x 10
–4
Torr, the
equation wuold be Pi = V
v+3
Torr/mbar.
Failure to use accurate pressure conversion data for N
2
or air to other gases can
cause an explosion due to over pressurization.
If the controller will measure any gas other than N
2
or air, before connecting the
controller to system control devices, adjust pressure outputs for the process gas that
will be used.
where Pi = pressure indication,
V = analog output voltage
and: the offset is factory adjusted for 0 V at 1 x 10
–4
Torr (1 x 10
–2
pascal)