Heath Consultants Optical Methane Detector (OM) - Manual (Page 32)

32
C
ALIBRATION
Verifying Calibration with External Cell:
The standard external calibration cell is 0.6 inches thick
internally. This is approximately 1/100
th of the entire external
light path (the distance between the two lenses) for a standard
crossbar. Therefore, the display will read 100 times lower than
the actual gas in this cell. Place this cell in the center of the
light path and observe the PPM reading on the display. The
display should read the value imprinted on the calibration cell
relative to the crossbar length you are using.
Again, if your OMD varies from calibration by more than
±
10% within a range of 1 to 100 PPM, it should be examined by
a trained technician.