Detcon TP-524C User Manual

Page 14

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.

Apply the calibration test gas with the humidifying tube installed at a f low rate of 200 to 500 milliliters per

minute (200ml/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 min-

utes of gas application, the sensor must satisfy a minimum resistance change which represents an “in range” sen-

sor response (see NOTE 2 below). Then the “Auto Span” cycle is programmed for 2.5 full minutes of exposure at

which point an auto-adjustment is triggered. If, for example, automatic calibration is set for 25 ppm and the sen-

sor response after 2.5 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. This continues for up to a maximum of 5 minutes total.

NOTE 1: If the sensor does not stabilize within 5 minutes during AutoSpan, the sensor will enter into “Stability

Fault”, and alternate between “STABILITY FAULT” and sensor’s current reading.

NOTE 2: 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 3: 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 4: When a “zero fault”, “stability fault”, or “range fault” occurs, the 4-20 mA signal reports a 0 mA value

to indicate there is a Fault condition that needs to be corrected.

3.7.3

Additional Notes

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.

If during calibration the sensor circuitry is unable to attain the proper span adjustment, the sensor will enter into

one of the calibration fault modes which will activate the fault LED, output a 0 mA signal, and cause the display to

alternate between the sensor’s current status reading and the calibration fault screen which appears as either:

“STABILITY FAULT, ZERO FAULT, or RANGE FAULT”.

If this occurs you must 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.

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.

3.8 S

TATUS OF

ROGRAMMING

, C

ALIBRATION

EVEL

, H

EATER

EVEL

, R

ANGE

AND

ENSOR

IFE

The programming menu has a “View Program Status” listing that allows the operator to view the present gas, range,

and software version number of the program, as well as the calibration gas level setting, heater level, range of detec-

tion, and estimated remaining sensor life. The programming menu functions also allow the programming of the cali-

bration gas level setting (see section 3.7.2), the sensor heater level (see section 3.6.2), the range of detection (see sec-

tion 3.6.4), and the utility menu for factory adjustments (see section 3.6.6).

Detcon Model TP-524C Hydrogen Sulfide Sensor

PG.14