INFICON Sensistor ISH2000 Hydrogen Leak Detector - Manual (Page 58)

Sensistor ISH2000 Technical Reference Manual (TRM) EN- 58
C 300
Calibration procedure
Before calibration, the Reference Value in the Calibration Menu must be set.
See “With reference gas” and “With reference leak” below.
When calibrating, expose the probe to the background air then do the follow-
ing steps:
1. First Menu then Calibration/Calibrate/Enter.
2. Push the Start button or push the probe button.
3. Expose the probe for the reference gas/leak
The probe does not have to be exposed to the to the calibration gas during the
whole Calibration Time ( the time set in the Calibration Menu while the bar
is moving). The instrument only measures the change as the probe goes from
the background air to calibration gas.
While the calibration time bar is moving, the probe should be exposed to the
calibration gas or referenece leak. Then the display shows Detecting Gas and
gives sound signals. Save or repeat the calibration routine until you can save the
calibration. If the calibration is not saved, the instrument will revert to the previ-
ous value after one minute.
Note: You will need to repeat the calibation 2-3 times to get Calibration OK
after changing setup or probe.
• Allow at least 30 seconds between each calibration for best accuracy!
• If the message “No Gas or Unstable Signal” is displayed repeatedly - go back
to Detetion Mode and check functionality.
• If Repeat Calibration is displayed then this means that the measured value
devated more than 10% from the previous calibration. Repeat the calibration
procedure.
Also set the Analysis Unit to the same as the Reference Value. If you want to
use another unit you have to put a recalculation number into Correlation Value
which describes the relationship between the different units.
Calibration intervals
Calibration is a natural part of leak measurement and an important factor in
quality assurance. It is impossible to specify an exact requirement for the inter-
val between the calibrations becase the applications for which the instrument is
used can vary considerably.
There will be some oxidation of the probe sensor, which reduces the sensitivity,
if the probe sensor:
• is not subjected to gas for a lengthly period or
• is exposed to a very small gas concentration (less than 10 PPM) with long
intervals between exposure.
If the instrument is subjected to a very large gas concentration over a long
period, a certain amount of insensitivity can occur directly afterwards. This satu-
ration can make it difficult to detectvery small leaks. Therefore, make it a habit
of removingthe probe from the measurig point as soon as the measured value is
displayed. This gives the detector an opportunity to recover.
Low sensitivity warning
The Detector will warn if sensitivity of sensor is too low to safely detect a leak
equal to the set Reject Level limit. The warning can be ignored and calibration
updated but the CAL_CONF output will not be set.