Detcon TP-624C - Manual (Page 17)

3.7.4 Calibration Frequency
In most applications, monthly to quarterly calibration intervals will assure reliable detection. However, industrial
environments differ. Upon initial installation and commissioning, close frequency tests should be performed, weekly
to monthly. Test results should be recorded and reviewed to determine a suitable calibration interval.
3.7.5 Sensor Linearization
Sensor linearization is a function performed via a two point calibration process that optimizes the microprocessors
ability to interpret a sensors response curve. The “Linearize Sensor” feature is performed at the factory and is not a
service requirement once a sensor is in the field. However, for optimum full scale accuracy, it is recommended that
a “Linearize Sensor” procedure be performed on an annual basis or upon replacement of the sensor (PN 3998-B).
To perform a “Linearize Sensor” procedure, follow the instructions below.
Material Requirements
* Detcon PN 3270 MicroSafe™ Programming Magnet
* Detcon PN 6038 Threaded Calibration Adapter
* Span gas containing the 10 ppm H2S gas in air. Nitrogen mixtures are not acceptable.
* Span gas containing the 50 ppm H2S gas in air (for 0-100 ppm ppm & 0-50 ranges). Nitrogen mixtures are not
acceptable.
* Span gas containing the 20 ppm H2S gas in air (for 0-20 ppm range). Nitrogen mixtures are not acceptable.
* Detcon PN 985-241100-321 Perma-Pure humidify tubing.
a) 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 Cal Level, Set Heater
Level, Set Range, and Linearize Sensor.
b) From the programming menu scroll to the Linearize Sensor listing. The menu item appears as: “LINEARIZE
SENSOR”. Enter the menu by holding the programming magnet stationary over “PGM 1” for 3 seconds
until the display reads “Apply 10 PPM H2S” , then withdraw the magnet.
c) Apply 10 ppm H2S at a controlled f low rate of 200-500 ml/m (200cc/min is the recommended f low). The dis-
play will report a value reading during the linearization check that reads “LinCheck ## PPM”. The actual
reading is unimportant. After waiting approximately 3 minutes for the 10 ppm sample to stabilize, the display
will then ask for either a 20 ppm gas sample (if programmed for 0-20 ppm range) or a 50 ppm gas sample (if
programmed for 0-50 ppm or 0-100 ppm range), “Apply ## PPM H2S”.
d) Apply the H2S gas sample at a controlled f low rate of 200-500 ml/m (200cc/min is the recommended f low).
The display will report a value reading during the linearization check that reads “LinCheck ## PPM”. The
actual reading is unimportant. After waiting approximately 3 minutes for the sample to stabilize, the display will
change to “Remove Gas ## PPM” and when the unit clears to < 5 ppm a “Linearization OK” message
will appear indicating a successful completion. Immediately following linearization, a normal span calibration is
required and prompted by the sensor. Apply your regular span gas as described in section 3.7.2g. Upon comple-
tion of the span calibration, the unit will return to the “LINEARIZE SENSOR” menu.
f) 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.
NOTE 1: If during this operation no gas is applied or the circuitry is unable to adjust the linearization to the
proper setting the sensor will enter into the calibration fault mode which will cause the display to alternate
between the sensor’s current status reading and the calibration fault screen which appears as: “CAL FAULT”
(see section 3.7.3).
3.8 S
TATUS OF
P
ROGRAMMING
, A
LARMS
, C
ALIBRATION
L
EVEL
, RS-485 ID, H
EATER
L
EVEL
, R
ANGE
,
AND
S
ENSOR
L
IFE
The programming menu has a programming status listing that allows the operator to view the gas, range, and soft-
ware version number of the program, as well as the current alarm settings, calibration gas level setting, RS-485 ID
Detcon Model TP-624C Hydrogen Sulfide Sensor PG.17