- Ion gauge "Off After Low Emission" error message appears in Tune Status and Vacuum Control page
- Cannot switch on the ion gauge; no vacuum reading is possible
- AutoSpec Ultima
- AutoSpec Premier
The ion gauge filament is open circuit and/or is shorting to ground.
FIX or WORKAROUND
- Check the resistance of your meter leads before making any measurement; touch the black and red measurement leads together.
- The resistance reading should be very low—optimally, less than one Ohm.
- Measure the resistance between pins 7 and 8 on the ion gauge end flange.
- Expect to see a resistance less than 1 Ohm, take into account the resistance of the meter leads as above. This would show the filament is good.
- If the resistance is very high/infinite or open circuit, the filament has failed and must be replaced.
- Part number for the Ion Gauge Filament: 7991802 - IR23 FILAMENT (VIG 8)
- Part number for the complete Ion Gauge Assy: 6060920 - GAUGE ION VIG 8 KF40
- If the resistance is good (less than 1 Ohm), suspect a grounded internal filament (short circuit).
- Measure the resistance from either pin 7 or pin 8 to the instrument housing/ground.
- Expect to see a high, open-circuit resistance. This is the normal condition.
- A low resistance indicates a short circuit, which needs to be rectified.
- The ion gauge must be removed following all vacuum handling procedures, and the short must be cleared by carefully adjusting the filament.
- NOTE: Never touch the ion gauge filament with bare hands. The filament is thorium-coated and mildly radioactive.
- It is possible that no resistance will be seen when you make the measurement to ground. The filament may be in close proximity to the instrument housing, making a real connection only when voltage and current are supplied.
- If the Analyzer region shows the error, test both ion gauges for a short to ground.
- Disconnect the Analyzer 2 ion gauge connector (BB350), and try to turn on the Analyzer 1 ion gauge. If a reading is seen, the problem is in the Analyzer 2 ion gauge.
- Likewise, disconnect the Analyzer 1 ion gauge connector (BB150), and try to turn on the Analyzer 2 ion gauge. If a reading is seen, the problem is in the Analyzer 1 ion gauge.
See article WKB96022 on how an ion gauge works.