ENMET ISA-M - Manual (Page 11)

ISA – M ENMET Corporation
9
6.0 Routine Gas Test and Recalibration 6.0 Routine Gas Test and Recalibration
Perform this test at regular intervals, you decide how often; we recommend that you do it at least every six weeks.
N OTE : The gases should be identical, or equivalent (correlation gas) to those used to initially calibrate the unit, unless
you want to recalibrate to a new gas or different concentration. In addition, calibration gases must be in a
background of air; do not use gases with an inert gas background (such as nitrogen or argon).
6.1 Test
Y OU NEED :
§ Cylinder of high-level calibration gas with air used as background gas (for example 200 ppm CO in air)
§ Calibration fixture (with humidifier/regulator, plastic tubing and calibration cup); ENMET part # 03700-001
§ Clean water
§ Small screwdriver
Figure 5: Exposing a Sensor to Test or Calibration Gas
P ROCEDURE :
1. The unit must operate continuously for at least 24 hours before this test.
2. After 24 hours, turn the HORN O FF .
3. On units requiring purging, rotate switch to P URGE ON, purge for 20 minutes. After the purge, rotate switch to
H ORN OFF, wait 20 minutes for the sensor to stabilize.
4. Fill the humidifier bottle with tap water about half-way.
5. Attach the calibration fixture to the high-level gas cylinder. Set humidifier upright on a level surface.
6. Open the valve to allow a steady stream of gas to bubble through the water.
7. Put the cal cup of the calibration fixture over the sensor. Let the gas flow over the sensor until the alarm triggers.
Use Table 5 for the approximate allowable time period until alarm:
Sensor
Enclosure
Sensor
Gas Cylinder
Regulator
Humidifier
Calibration Cup
To Cal Cup
Top View of Humidifier
To Regulator