D397-01-880 Issue E
Page 26
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Operation
4.8.6
Active Strain Gauge (ASG) control
Note:
For a detailed specification and instructions regarding the use of the ASG, refer to the Instruction Manual
(D357-25-880).
Active Strain Gauges are gas independent diaphragm gauges. There are two gauges with full scales of 2000 and 1000
mbar (1500 and 750 Torr) respectively. Both gauges measure pressures down to 1 mbar (7.5 x 10
-1
Torr), have a linear
pressure characteristic and output voltage directly proportional to the pressure. The output is 0 to 10 V d.c. over the
measuring range of the gauge.
ASG has menu options in addition to those shown. (Refer to Default setup options (all gauges)
. (Refer
).
Figure 20 - Gauge setup screen ASG
Please refer to
for the error and diagnostic information for the ASG.
Table 17 - Error/diagnostic monitoring ATC-E
Diagnostic messages
Description
Over Range
(Gauge output >11.000 V)
Indicates that either the measured gas pressure is outside the range of the
gauge, or that there is a fault with the gauge.
Clear the error message, reduce the process pressure to within the range of the
gauge, scroll to the gauge display line and press 'Cycle'. If the gauge fails to
give a pressure readout it should be replaced.
This is most likely to occur with gases of low molecular weight such as Helium.
Under Range
(Gauge output <1.500 V)
Indicates that the gauge is faulty and should be replaced.
Table 18 - Setup options ASG
Menu option
Description
Range
Indicates full scale of available gauge options.
Choice of: 1000 or 2000
Set zero
Allows the user to zero the gauge.
Reduce the system pressure to 2 x 10
-2
mbar (1.5 x 10
-2
Torr) or below for the
2000 mbar (1500 Torr) ASG or 1 x 10
-2
mbar (7.5 x 10
-3
Torr) or below for the
1000 mbar (750 Torr) ASG.
'Scroll' to 'Set zero' and press 'Select'.
'Command Sent' appears for 1 s to confirm instruction has been carried out.
Display
Indicates pressure display options.
Choice of:
Float (mantissa and exponent).
Fixed (number to 1 decimal place).
