7 Service and Maintenance
62
Series 340 Vacuum Gauge Controller
Instruction Manual - 340005 - Rev. D
7.3.5 Electrometer Troubleshooting
The electrometer design is based on a log-type amplifier, and conversion is accomplished via a
dual-slope A/D converter.
Table 7-5 Electrometer Module Troubleshooting
Symptom
Possible Cause
Corrective Action
The pressure reading displayed on the
front panel of the 340 controller is less
than the system is capable of producing,
but the ion gauge appears to operating
normally.
1. The collector cable is not
connected to the ion gauge.
2. The collector cable is shorted or
defective.
1. Connect the cable.
2. Check the continuity of the cable
and replace or repair the cable.
The pressure reading displayed on the
front panel of the 340 controller is
higher than the expected system
pressure or the display is erratic.
1. The inside ion gauge may be
contaminated.
2. Current leakage from the +180V
grid.
Clean (degas) or replace the ion
gauge. If necessary, install a baffle in
the vacuum system connection for
the gauge to minimize materials from
the process entering the gauge.
The displayed pressure reading is blank
or erratic.
Defective electrometer PCB.
Check the A/D Failure, µP Failure,
Underrange, and Overrange
indicator LEDs on the electrometer
PCB. See Figure 5-1 on page 46. If
illuminated, replace the electrometer
PCB.
Figure 7-2
Electrometer Module - Top View (Controller Cover Removed)
