GDS GDS-68XP, Operation And Maintenance Manual, Page: 33 / 68

GDS-68XP Operation & Maintenance Manual, Revision 3.5
Page 33
FAULT AND OVERRANGE CONDITIONS
The GDS ‐ 68XP contains multiple microprocessors that monitor flow rates and sensor readings to detect
problems. In the event that a fault occurs during a sample sequence, the 4 ‐ 20mA output will indicate one
the following fault condition:.
POWER UP Immediately after power ‐ up the GDS ‐ 68XP outputs 0mA (FAULT) for 8 seconds and then
4mA (“0”) until the first reading is successfully recorded. This allows a remote device to determine if the
GDS ‐ 68XP was forced to restart as a result of a power failure.
INPUT OVERRANGE FAULT To protect the electrochemical sensor in the event of an over ‐ range
condition during a sample measurement sequence, the sample valve will automatically and the purge air
pump will be activated to force fresh air into the sensor cell.
SENSOR RECOVERY FAULT After the sensor output is monitored for a prompt return to zero. If the
output does not return to a value of less than 10% of full scale during the recovery interval, the sensor
may be saturated with sample gas and the GDS ‐ 68XP will indicate a “recovery fault”
PEAK ALGORITHM FAULT – During the sample sequence, the GDS ‐ 68XP looks for a level peak value. If
no level peak is found, the GDS ‐ 68XP will indicate an “algorithm fault”.
SAMPLE OR PURGE AIR FLOW FAULT If the sequencer senses a lack of flow for more than 10
seconds during the sample sequence, the GDS ‐ 68XP will indicate a “flow fault”.
CALIBRATION FAULT – If the sensor output higher than 10% of scale, or lower than ‐ 10% of scale when
a sequence starts the GDS ‐ 68XP will indicate a “calibration fault”. The GDS ‐ 68XP will also indicate a
“calibration fault” if the GASMAX is placed in Cal Mode at any time during a sample sequence.
SENSOR FAIL FAULT If the sensor is removed or fails in such a way as to cause a channel 1 sensor
FAULT reading during a sample or sequence, the GDS ‐ 68XP will indicate a “sensor fault”.
FAULT REASON % OF
SCALE
OUTPUT
(MA)
RANGE:
0 ‐ 3.00
RANGE:
0 ‐ 100
OVER ‐ RANGE INPUT EXCEEDS MAX RANGE VALUE 105% 21MA “3.15” “105”
RECOVERY FAULT SENSOR FAILS TO DROP BELOW 10% ‐ 15% 1.6 MA “ ‐ 0.45” “ ‐ 15”
PEAK FIND FAULT PEAK FIND ALGORITHM TIMES OUT ‐ 17.5% 1.2 MA “ ‐ 0.52” “ ‐ 17.5”
FLOW FAULT GAS OR PURGE AIR FLOW DISRUPTED
FOR > 10 SECONDS
‐ 20% 0.8 MA “ ‐ 0.60” “ ‐ 20”
CALIBRATION
FAULT
GASMAX CAL DURING SEQUENCE OR
SENSOR INPUT > 10% OR < ‐ 10% OF
SCALE AT START OF CYCLE
‐ 22.5% 0.4 MA “ ‐ 0.67” “ ‐ 22.5”
SENSOR FAULT SENSOR BAD OR IN FAULT ‐ 25% 0.0 MA “ ‐ 0.75” “ ‐ 25”
Figure 8-1: Fault Conditions