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The Calibration Function
Overview
If greater than standard accuracy is desired, the factory's default calibration factor of 1.000 may be adjusted by
performing the calibration procedure as described below, and then selecting the monitor's CAL function to enter
the new calibration factor.
IMPORTANT! Changing the calibration factor will VOID the factory calibration. Typically, the monitor will remain
within the factory-calibrated accuracy indefinitely and no calibration is required. Complex software algorithms
adjust for temperature drift, IR source aging, and pressure changes in order to keep the unit within factory
accuracy specifications.
Calibration Procedure
The calibration 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, 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 a certified calibration gas must be used to ensure sampling occurs at ambient conditions.
A minimum sample size of 5 liters is required.
The AGM-SZ should be operating for at least one hour prior to performing a calibration.
Prepare the AGM-SZ for sampling by using the CAL function to set the calibration factor to 1.000. Also, use the
LOG INT function to set the log interval to 1 minute.
With the AGM-SZ operating normally, connect the gas-sample bag directly to the gas-inlet port and allow the
monitor to sample the entire bag. When sampling is complete, view the logged ppm values using the PPM LOG
function. If the bag was large enough for multiple samples, average the most stable ones. The new calibration
factor is computed by dividing the known gas concentration value by the measured value. Typically this number
will be between 0.95 and 1.05. Use the CAL function as described below to enter the new calculated
calibration factor
Adjusting Calibration Factor
From the Data Display screen, use the Keypad buttons to place the arrow (>) on the display next to the CAL
function. Then press ENTER to display the Calibration screen.
R717 CALFACTOR
1.000
With the Calibration screen displayed, use the Keypad buttons to enter the new calibration factor.
Press ENTER to save this value.
22
Instruction 3015-4286
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