Calibration Procedure
The CAL FACTOR is determined by sampling a known dilution of ammonia gas. The sample must be prepared to less than half the desired accuracy, and the concentration must be corrected for ambient temperature and pressure at the time of measurement.
Calibration is best performed at or near full scale (10,000 PPM). It can, however, be done at any concentration, and ideally in the range where maximum accuracy is desired down to, but not below, 100 PPM.
A cylinder of ammonia gas at a certified PPM level must be used to assure sampling occurs at ambient conditions. A minimum sample size of 5 liters is required.
The AGM should be operating for at least one hour prior to performing a calibration.
Prepare the AGM300 for sampling by initially setting its CAL FACTOR to 1.000 (Page 57). Next, set up the AGM300 for a logging interval of zero minutes (Page 42), and place the AGM300 in its zone hold mode for the zone you wish to set up (Page 45).
Connect the sample bag directly to the intake port for the zone you have set up and allow the AGM300 to sample the entire bag. When sampling is complete view the trend data for the zone used to sample (Page 53). Read the measured PPM by placing the cursor on the spikes cause by the sample. If the bag was large enough for multiple samples, average the most stable ones.
The new CAL factor is computed by dividing the known gas value by the measured value. Typically this value will be between 0.95 and 1.05. Enter the computed CAL factor into the monitor using the ADM800 (Page 57) or PC interface. This value is stored in
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