Detcon TP-624C - Manual (Page 16)

a) Verify the current calibration gas level setting as indicated by the programming status menu. To do this, follow
the instructions in section 3.8 and make note of the setting found in listing number 12. The item appears as
“CalLevel @ xxPPM”.
b) If the calibration gas level setting is equal to your calibration span gas concentration, proceed to item “f”. If
not, adjust the calibration gas level setting so that it is equal to your calibration span gas concentration, as
instructed in items “c” through “e”.
c) Enter the programming menu by holding the programming magnet stationary over “PGM 2” for 15 seconds
until the display reads “VIEW PROG STATUS” , then withdraw the magnet. At this point you can scroll
through the programming menu by momentarily waving the programming magnet over “PGM 1” or “PGM 2”.
The menu options are: View Program Status, Set Alarm 1 Level, Set Alarm 2 Level, Set Heater Level, Set Range,
and Linearize Sensor.
d) From the programming menu scroll to the calibration level listing. The menu item appears as: “SET CAL
LEVEL”. Enter the menu by holding the programming magnet stationary over “PGM 1” for 3 seconds until
the display reads “CalLevel @ ##PPM” , then withdraw the magnet. Use the programming magnet to make
an adjustment to “PGM 1” to increase or “PGM 2” to decrease the display reading until the reading is equal to
the desired calibration span gas concentration. Exit to the programming menu by holding the programming
magnet over “PGM1” for 3 seconds.
e) Exit back to normal operation by holding the programming magnet over “PGM 2” for 3 seconds, or automati-
cally return to normal operation in 30 seconds.
f) Enter the calibration span menu by holding the programming magnet stationary over “PGM 1” for 3 seconds
The display will read “1-SPAN 2-EXIT” Hold PGM 1 for 3 seconds to proceed with a span or hold PGM 2
for 3 seconds to exit back to normal operation mode. After choosing span you may, within 1 minute, abort the
span procedure by a 3 second hold on PGM 2.
g) Apply the calibration test gas with the humidifying tube installed at a f low rate of 200 to 500 milliliters per
minute (200cc/min is the recommended f low). The display will read “AUTO SPAN xxPPM” . The “xx” part
of the reading will change in single-digit increments as the sensor responds to the test gas. During the f irst 2
minutes of gas application, the sensor must satisfy a minimum resistance change which represents an “in range”
sensor response (see NOTE 2 below). “Auto Span” cycle is programmed for 3 full minutes of exposure at which
point an auto-adjustment is triggered. If, for example, automatic calibration is set for 25 ppm and the sensor
response after 3 minutes is 17 ppm, the auto span function adjusts the reading to 25 ppm. After this adjust-
ment, stability is verif ied for a period of 30 seconds. If less than 3 ppm of change occurs within the 30 second
time, then auto span is completed and the display reads “REMOVE GAS” . Remove the gas sample and
observe that the display clears to a reading of 0 ppm in less than 2 to 3 minutes.
If instability is greater than or equal to 3 ppm, auto span makes another adjustment and an additional 30
second period is allowed for f inal stabilization.
NOTE 1: If the sensor does not clear to <10% of range in <5 minutes after completing a span calibration, the
sensor will enter into a calibration fault mode which will cause the display to alternate between “ZERO
FAULT” and the sensor’s current reading.
NOTE 2: If the sensor fails the minimum signal change criteria, then a “RANGE FAULT” message will be dis-
played alternately with the sensor’s current reading.
NOTE 3: When a “zero fault”, or “range fault” occurs, the sensor microprocessor retains its previous calibration
references.
3.7.3 Additional Notes
1. Upon entering the calibration menu, the 4-20 mA signal drops to 2 mA and is held at this level until the pro-
gram returns to normal operation.
2. If during calibration the sensor circuitry is unable to attain the proper span adjustment, the sensor will enter into
the calibration fault mode which will activate fault alarm functions (see section 3.10) and cause the display to alter-
nate between the sensor’s current status reading and the calibration fault screen which appears as either: “ZERO
FAULT, or RANGE FAULT”. If this occurs you may attempt to recalibrate by entering the calibration menu as
described in section 3.7.2-f. If the sensor fails again, defer to technical trouble shooting.
Detcon Model TP-624C Hydrogen Sulfide Sensor PG.16