ENMET ISA-44-RALE-OD - Manual (Page 28)

ENMET Corporation ISA-44RALE-OD/ISA-44RAHE-OD/ISA-44E-OD
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6.3.2 Recalibration Procedure
Recalibration involves verifying and/or setting the sensor voltage. If the sensor is located 10 feet or more from the control
unit, sensor voltage specified in this procedure must be measured initially across the brown and orange wires inside the
sensor assembly (you may have already done this during installation).
Once the voltage has been set correctly at the sensor, then measure the corresponding voltage across the heater (positive;
red) and ground (negative; black) test points on the display plate of the unit. Record this voltage (you have probably
already done this during installation). Now whenever the sensor voltage must be corrected, all you need to do is adjust the
voltage so that you gain your recorded voltage across these test points. If the sensor assembly is closer than 10 feet from
the unit, simply measure the sensor voltage specified in this procedure across the heater and ground test points on the
display plate of the unit.
PROCEDURE : Recalibration
1. Purge in clean air.
N OTE : For units without PURGE, allow 15 minutes for the sensor to recover and stabilize.
2. After the purge, turn PURGE off and wait one hour for the sensor to stabilize.
3. Repeat steps 6-10 in the Test Procedure (Section 6.3.1).
4. After the proper time exposure to the calibration gas, adjust the meter/gain adjust pot. (R33..see Fig.7) until the
meter reading corresponds to the low-level gas concentration. For example, 35 ppm CO calibration gas requires a
meter reading of 35 ppm CO.
5. Next, adjust the high-level alarm set pot. (R34) until the alarm just barely triggers.
N OTE : Begin this adjustment from a non-alarm condition.
6. Repeat step 5 slowly to verify the alarm adjustment. Leave the pot. next to the alarm point on the alarm side.
7. Turn off the calibration gas.
8. Turn the Horn back on.
6.3.3 Precautions
♦
It is necessary to have at least ten percent (10%) relative humidity content, or greater, in the test gas for accurate
testing and calibration. The water in the humidifier bottle provides this humidity.
♦
All units factory calibrated to alarm below 300 ppm for any gas in moist air may take up to five minutes to
generate the alarm in a static environment containing the specified gas concentration.
♦
Do not adjust for an instantaneous alarm when the test gas is first released; do not let gas flow at a high rate. If you
do, the calibration will be inaccurate and the sensor will be overly sensitive.
♦
When using gas other than ENMET calibration gas: do not use test gases with 100% nitrogen as background gas;
do not use totally dry gases directly from large high pressure cylinders.