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H25-IR Calibration
Instruction 3015-4342 23
3.2 Internal Calibration
Internal calibration uses the instrument’s built-in leak source. Properties of the leak source (i.e. gas type,
leak rate, temperature coefficient, and specification temperature) are entered at the factory and do not
need to be changed by the operator.
The properties of the leak source along with the current internal temperature of the instrument are used
to compute the actual leak rate when a calibration is requested. This number is displayed as the “target”
value during calibration. A spring switch located in front of the CAL Port ensures that the probe is kept in
place for the duration of the calibration process. Calibration will fail if the probe is withdrawn too early in
the process, or if the computed parameters deviate from the stored factory calibration by more than 20%.
1. Turn ON instrument and allow it to complete its 120 second warm-up.
2. Press the front panel CAL button to display the Calibration screen. Note that the display must be
reading a leak rate of “0.00” when the CAL button is pressed; otherwise, the message “LEAK
RATE MUST BE ZERO TO CALIBRATE” will appear. If necessary, press the ZERO button to
zero the display before pressing CAL.
3. Ensure that the instrument is set up for internal calibration as indicated by “INT CAL” being
displayed at the bottom-right of the display. If “EXT CAL” (external calibration) is displayed,
perform the procedure in Section
3.1 Selecting Internal or External Calibration and set the Cal
Type to Internal.
4. Insert the probe tip into the CAL Port within 10 seconds
after pressing the CAL button. Be sure that the probe tip
makes contact with the spring switch. At this time the
calibration process should automatically start.
The top number of the Calibration screen shows the
“target” value (leak source rate), while the bottom
number shows the current measured value. Keep the
probe tip firmly against the back of the port for the
duration of the calibration process, during which time the
instrument is calibrated at both a high and low flow rate.
If the probe tip looses contact with the spring switch before the
calibration process completes, the message “CAL ABORTED” is
displayed. At this time press any key to retain the previous
calibration curve and return to the Data Display screen.
5. After a successful calibration the new calibration data is saved
and the message “CAL OK” followed by “WITHDRAW PROBE
FROM LEAK SOURCE” will appear.
6. Withdrawing the probe causes the display to switch back to the
Data Display screen. Note, however, if the PCHK Mode is set to
AUTO (refer to Section
2.4.7 PCHK Mode), then a pressure check
is performed prior to the display of the Data Display screen.
NOTE: After being calibrated the instrument is automatically
placed into its Search mode.
C
AL
OK
Oz/yr
R134A
SETUP
INT CAL
WITHDRAW PROBE
FROM LEAK
SOURCE
Oz/yr
R134A
SETUP
INT CAL
Oz/yr
R134A
SETUP
SM SRCH
0.00
Oz/yr
R134A
SETUP
INT CAL
TARGET
O/YR
R134A
MEASURED
O/YR
0.89
Oz/yr
R134A
SETUP
INT CAL
0.89
TARGET
O/YR
R134A
MEASURED
O/YR
INSERT
PROBE
PCHK