Det-Tronics MOS H2S Gas Sensor - Manual (Page 21)

95-8532 1.4 19
Description
Normal operation/no gas present
Initiate calibration
Zero calibration complete
Span calibration
Span calibration complete
Calibration fault indication
Display
Indicates the detected gas
concentration
Sequences through the Setup
settings
Enters the Calibration mode -
Display shows detected gas
concentration and alternating
message:
“ZERO” “CAL”
Display shows detected gas
concentration and alternating
message:
“APLY”
“GAS”
Display shows rising gas
concentration and alternating
message:
“GAS”
“ON”
Display shows decreasing
gas concentration when gas
is removed and alternating
message:
“CAL” “OK”
then
“RMV”
“GAS”
then, if the calibration is
successful:
“XXXX SPAN”
Display shows alternating
messages indicating the fault,
then
“RMV”
“GAS”
Operator action
• If the possibility of background gases exists, purge the
sensor with clean air to ensure accurate calibration.
• Hold the Cal magnet to the CAL/RESET magnetic
switch for 7 seconds. See Figure 11 for CAL/RESET
switch location. (The external reset input can also be
used to enter the calibration mode if “EXT CAL YES”
was selected during Setup procedure).
• Apply the calibration gas to the sensor. Ensure proper
H
2
S ampoule is inserted into ampoule holder within
calibration bottle. Place cal bottle over MOS sensor.
Break ampoule by tightening thumb screw. Rotate
mixing fan by slowly rotating the external lever 360°.
• Continue slowly rotating the mixing fan.
• Remove the calibration gas. When the gas level
falls below the lowest alarm setpoint, and if no
faults are present, the transmitter automatically
exits the Calibrate mode.
• Upon completing of calibration, a 4-digit number
preceeding the word “span” is displayed (for only
7 seconds). This value represents overall sensor
sensitivity and should be noted by the operator
and logged for future reference. (This number
is used for trending purposes only.) Any reading
over 100 indicates that the sensor is good.
• At the successful completion of the calibration,
all outputs and indicators return to normal
operation.
• If faults are present, the unit will exit after the
remainder of 10 minutes.
• If a fault occurs, remove the gas and correct the fault.
After the fault has been cleared, begin calibration
again. See Table 8 - Fault Messages, Explanations
and Corrective Action.
Table 7—Automatic Calibration Procedure