GDS-68XP Operation & Maintenance Manual, Revision 3.4
Page 50
11
TROUBLESHOOTING GUIDELINES
FAULT INDICATION ON OUT PUT CHA NNEL (CH2)
•
Value shows +105% of scale – indicates an
OVERRANGE
condition, where the sample gas caused
the sensor to read more than 100% of scale.
•
Value shows -15% of scale – indicates a
NON-RETURN-TO-ZERO FAULT
during recovery mode.
Indicates sensor may be saturated with target gas. Increase the purge interval to allow more time
for the sensor to recover.
•
Value shows -17.5% of scale – indicates a
SAMPLE PEAK IDENTIFICATION ALGORITHM FAULT
;
peak was not found in maximum allotted time. Check sample flow rates and sensor life.
•
Values shows -20% of scale – indicates a
LOSS OF FLOW
for more than 10 seconds during sample
pre-charge or sample recovery. Check sample flow or pump performance.
•
Value shows -22.5% of scale – indicates a
CALIBRATION
fault – either the resting input value at
the start of the last cycle was higher than 10% of scale OR a GASMAX calibration occurred during
the cycle.
•
Value shows -25% of scale – indicates
SENSOR FAULT
from GASMAX monitor.
FAULT INDICATION ON RAW SENSOR CHA NNEL (CH1)
•
Fault or Overrange on power-up. Certain toxic sensors indicate off-scale low or high at power up
and quickly drift towards zero. This is normal behavior.
•
Continuous Fault indication. Remove sensor and examine for moisture or discoloration. Replace
sensor if wet or discolored. Fault indication generally indicates sensor useful life is exhausted.
•
Sensors left unpowered for more than 3 months are subject to accelerated degradation and may
demonstrate a permanent loss of sensitivity.
SENSOR FAILS CA LIBRATION
•
Sensor reading during zero calibration exceeds upper limit of zero – sensor is defective and
should be replaced.
•
Sensor reading during span calibration too low – sensor may be defective. However, it may be
possible to
temporarily
continue operation by increasing PREAMP GAIN.
GDS-68XP A ND RECEIVING DEVICE DISPLAYED VALUES DON’T MATCH
•
Check that zero and full scale range values match between GDS-68XP and receiving device
(controller). Use DIAGNOSTICS menu to force the OUTPUT channel (Ch2) to 12mA and verify
half-scale reading on remote controller.
•
Check for high impedance shorts to ground on 4-20mA wiring.
