ENMET ISA-M - Manual (Page 12)

ENMET Corporation ISA – M
10
Table 5: Approximate Alarm Time
Gas or Vapor Time to Alarm
20 ppm CO 5 - 7 minutes
50 ppm CO 5 minutes
200 ppm CO 2 minutes
10% LEL methane 1 minute
20% LEL methane 1 minute
100 ppm vinyl chloride 1 - 2 minutes
typical hydrocarbon vapors 1 - 2 minutes
20% LEL propane 1 minute
8. After you verify the alarm response, turn the gas off and remove the calibration fixture from the gas cylinder.
9. Turn the switch back to OPERATE .
C AUTION : If steps 1 - 10 do not trigger the alarms, and no electrical or mechanical malfunction is apparent, you must
recalibrate the instrument.
6.2 To Recalibrate
1. Wait 8 - 10 minutes for the sensor to recover from the test.
2. Repeat steps 3 - 7 as outlined in the test procedure above using the high level calibration gas.
3. With the gas still flowing, adjust the Meter Adjust potentiometer (Ref. Fig. 2) R33; ccw to increase, cw to
decrease meter reading) with a small screwdriver.
•
You want to have the meter pass through the low level alarm point, to verify that the alarm light triggers.
•
If it does not, set the meter to the low alarm point and adjust R35 ( low level alarm POT ).
•
Then adjust the meter gain POT to pass through the high alarm point, verify that the alarm light triggers at the
high alarm point.
•
If it does not, set the meter gain to the high alarm point adjust R34 to trigger the alarm light.
•
Turn the switch to OPERATE for a second to verify the horn is operational. This sets the alarm points (Refer to
Figure 2).
C AUTION : D O N OT adjust for instantaneous alarm when test gas is first released. If you do, the calibration is inaccurate,
and the sensor is overly sensitive.
4. Shut off the calibration gas flow at the valve on the gas cylinder.
5. Remove the calibration gas, the flow of clean air should clear the unit from its gas alarm state in less than one
minute. After the alarms have cleared, turn the switch to OPERATE .
C AUTION : Do not use calibration gas with inert gases such as argon or nitrogen as a background. The background gas
must be "air" or equivalent.
C AUTION : Do not totally dry gases directly from high-pressure cylinders.