User Guide

Single Zone Gas Monitor
26 P/N: 3015-4256 Rev 10
3.10. The Calibration Function
3.10.1. 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.
3.10.2. Calibration Procedure
The calibration factor is determined by sampling a known dilution of 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 SZ unit should be operating for at least one hour prior to performing a calibration.
Prepare the 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 SZ monitor 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
3.10.3. 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.
With the Calibration screen displayed, use the Keypad buttons to enter the new calibration factor.
Press ENTER to save this value.
R134A CALFACTOR
1.000