Bacharach H25-IR - Manual (Page 31)

H25-IR Calibration
Instruction 3015-4342 25
3.4.1 Simulating Other Internal Leak Source Gas Types
Using the CAL Factor
When measuring the leak rate of a gas that is not the same as the instrument’s internal calibration gas, the CAL
Factor can be adjusted make the instrument’s internal calibration gas simulate the gas being measured. This
allows the operator to calibrate the instrument using the internal leak source, regardless of the gas contained in
the leak source. Note that this procedure is not necessary for single-gas instruments.
Material Required:
 Calibrated External Leak Source set up for 5 to 10 times the leak rate
that the instrument is expected to detect
IMPORTANT! Remember that the accuracy will not be better than that of the
external leak source used for calibration.
Procedure:
1. Turn ON the instrument and allow it to warm up for 30 minutes before proceeding.
2. Program the instrument for the Gas Type contained in the external leak source (refer to Section
2.5.1 Gas Type).
3. 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.
4. Perform an internal calibration in the normal way using the internal leak source (refer to Section 3.2
Internal Calibration). Note that it doesn’t matter that the gas in the internal leak source doesn't match
the Gas Type entered in Step 2.
5. Press the MODE key to place the instrument into its Measure mode.
6. Measure the leak rate of the external leak source and record the displayed reading.
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 6 Troubleshooting. 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.