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Calibration H25-IR
26 Instruction 3015-4342
7. Compute the new CAL Factor by dividing the actual leak rate of the external leak source by the
reading recorded in Step 6. For example, if the leak rate of the external leak source is 0.4 oz/yr and
the measured rate was 0.43 oz/yr, then the new CAL Factor is 0.4 ÷ 0.43 = 0.930.
This new CAL Factor establishes the relationship between the internal calibration gas and the gas
type selected to be measured.
8. Enter the new CAL Factor as described in Section 3.4.3 Adjusting the CAL Factor. Note that the
displayed Gas Type should match the gas selected in Step 2.
9. From this point on the operator can perform an internal calibration and get accurate
measurements for other gas types using whatever gas is contained in the internal leak source.
3.4.2 Improving PPM Measurement Accuracy using the CAL Factor
The CAL Factor can be adjusted to improve the accuracy of the ppm measurement by calibrating the
instrument on the gas being measured. The accuracy of the ppm measurement after performing this
procedure will equal the accuracy of the gas sample, ±1%. Note that the accuracy of the instrument’s ppm
measurement depends on the accuracy of the gas sample.
The new CAL Factor is determined by sampling a known dilution of gas whose accuracy is better than the
ppm measurement accuracy as stated in Section 7 Specifications. The concentration of the sample must
also be corrected for ambient temperature and pressure at the time of calibration. A minimum sample size
of 5 liters is required.
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.
The instrument should be operating for at least 30 minutes prior to performing a calibration.
Verify that the current CAL Factor is set to 1.000 by selecting the Main Menu > CAL DATA > CAL
FACTOR function. If necessary, reset the CAL Factor to 1.000. Refer to Section 3.4.3 Adjusting the CAL
Factor.
With the instrument operating in its ppm measurement mode (refer to Section 4.2.8 Measuring the PPM
Level), insert the probe tip into the gas-sample bag and allow the instrument to sample until the ppm
reading on the display is stable. At this time record the ppm reading. The new CAL 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. Enter the new CAL Factor as described in Section 3.4.3 Adjusting the CAL Factor.
IMPORTANT! If the instrument is switched back to measuring the leak-rate, then the instrument must be
recalibrated on the gas being measured.