971B UniMag™
34
Operation manual
Troubleshooting
Symptom
Possible Cause/Remedy
No digital communication
- Check electrical connections (3 wires from transducer to
communication equipment)
- Transducer and communication equipment baud rate
matches
- Use of incorrect transducer address. Try address 254
- Attention characters missing (@)
- Termination characters missing (;FF)
NAK180 is received when
transmitting setpoint commands
- The transducer setup is locked. Refer to disable lock
procedure page 19
Incorrect pressure value
- Other gas present than transducer gas setting or trace of
gas.
- Contaminated sensor. Transducer repair required.
- Corroded sensor. Transducer repair required.
Incorrect pressure value at low
pressure.
- Contaminated sensor. Transducer repair required.
- Corroded sensor. Transducer repair required.
- Incorrect Vac adjustment has been executed.
Incorrect pressure value at high
pressure.
- Contaminated sensor. Transducer repair required.
- Other gas or gas trace present than transducer gas setting.
Cold Cathode does not provide
measurements.
- If the Cold cathode is turned on a low pressure <1.00E-7
Torr or is contaminated a delay can occur from turning on
high voltage to the ionization begins.
Cold Cathode value is lower than
actual pressure.
- If the Cold Cathode sensor has been operated a too high
pressure or exposed to fast pressure cycles the sensor can
be sputtered. Sputtering of sensor will normally provide
lower reading than actual pressure.
Set point relay does not trip.
- Setpoint not enabled.
- Setpoint value not set to proper value.
- Setpoint direction is different than the user expects.
- Check electrical connection.
- Check part number to see if transducer has setpoint relays.
No analog output
- Power supply turned off.
- Check electrical connections.
Status LED illuminating red
- Sensor element defect. Refer to Service and Repair page
35.