ENMET ISA-44-2OD - Manual (Page 20)

ENMET Corporation ISA-44-2-OD
16
5.2 Calibration
5.2.1 Toxic Gas Channel # 1
The following procedure is for checking the calibration level and for recalibrating the Carbon Monoxide(CO) Channel of
the ISA-44RAL-OD. Refer to Figure 2 and 4.
Perform A Complete Recalibration Periodically (at least monthly) and:
• When you replace the sensor.
• When the sensor encounters severe conditions (i.e., gross exposure to smoke or liquid hydrocarbon).
M ATERIALS
• Cylinders of calibration gas of known CO concentration in air (i.e. 20 ppm and 50 ppm CO in air.).
D O N OT use CO in an inert carrier gas, such as nitrogen or argon.
• Calibration gas fixture (with quick-disconnect fitting – ENMET part number 03605-001)
• Small screwdriver (for potentiometer adjustment)
• dc voltmeter
P ROCEDURE
1. Turn operation switch to H ORN O FF . Be sure humidifier bottle is filled with tap water to Water Level mark.
2. Turn operation switch to P URGE O N . Measure purge voltage across TB-6(+) and TB2-7(-). It should be 1.6 V DC +/-
.03 V DC . If not 1.6 V DC +/- .03 V DC , adjust Purge Adjust Potentiometer (see Figure 4) until desired reading is
shown. Turn operation switch to H ORN O FF and measure sensor heater voltage across TB2-6 and TB2-7. It should
now read 0.86 V DC +/- .03 V DC . If it is not 0.86 V DC +/- .03 V DC , adjust Heater Adjust Potentiometer (see Figure 4)
until desired reading is shown.
3. Turn operation switch back to P URGE O N . Purge at least one hour, up to overnight.
R EMEMBER : If you suspect contaminated air in your compressor system, use clean bottled air to supply the sensors with a
continuous airflow.
4. After purging, turn operation switch to O PERATE . Allow 30 minutes to stabilize.
5. Remove the compressed air line and insert the calibration apparatus (see Figure x).
6. Turn operation switch to H
ORN O FF . Open the regulator on the top of the high-level calibration gas cylinder. This
brings the gas into the sampling assembly.
7. Regulate the flow of calibration gas according to the "... SET " mark or between 7 – 12 PSI on the pressure regulator
dial.
8. Let the high-level calibration gas flow into the system for 5 minutes. This assures a full and balanced response from
the sensor. During this time, the meter should have risen above the low-level alarm point and the amber light should
have gone on.
9. With the gas still flowing, adjust the Meter Adjust Potentiometer with a small screwdriver (adjust this pot CCW to
increase, CW to decrease meter reading). You want to have the same meter reading as the calibration gas
concentration. This sets the alarm point. Refer to Figure 4.
Note: Do not adjust for instantaneous alarm when test gas is first released. If you do, the calibration will be
inaccurate, and the sensor will be overly sensitive.
10. Adjust the High Level Alarm Set Adjust Potentiometer CCW until the red alarm light is just barely triggered. At this
point, verify the audio alarm is operational by turning the operation switch to O PERATE momentarily.
N OTE : If red alarm light is on prior to the potentiometer adjustment, adjust this POT CW until the light deactivates,
then readjust CCW until the light just barely activates.
11. Shut off the calibration gas flow (at the regulator on the gas cylinder).
12. Allow pressure to equalize – wait until the pressure meter on the humidifier-regulator assembly reads zero. Remove
calibration fixture, and reconnect humidifier-regulator assembly to compressed air line. Allow air to flow over
sensor for 10 minutes to clear the sensor.
13. In a similar manner, apply the low level calibration gas for five minutes
14. While the gas is still flowing, adjust the Low Alarm Set Adjust potentiometer CCW until the amber alarm light just
activates.