INFICON Sensistor ISH2000 Hydrogen Leak Detector - Manual (Page 81)

EN- 81 Sensistor ISH2000 Technical Reference Manual (TRM)
E 130
E 130 Functional verification
Sensitivity Test
Sensitivity Test has been designed to help to double-check Hand Probe sensors
and H65 sensors for Sensistor ISH2000 before delivery to end customers. Every
sensor has been tested thoroughly before delivery from the factory. It happens,
however, that sensors lose sensitivity while kept in stock.
By following these instructions the user will get the information you need to
accept or reject a new sensor before delivery. The test is done using a reference
gas containing 10 ppm H2 in synthetic air.
You need the following equipment:
• Leak Detector (Sensistor ISH2000) with probe cable and hand probe.
• Reference gas 10 ppm H2 in synthetic air.
IMPORTANT:
A sensor can be calibrated using reference gas or a reference leak. There are
some fundamental differences between these two methods:
• When using a reference leak you add Hydrogen to the background.
• When exposing the sensor to reference gas you replace the background
(ambient) with the reference gas.
It is important, in both cases, to calibrate in a non-polluted background (i.e.
typically 0.5 ppm Hydrogen).
When using a reference gas this is essential. If the background is close to the
concentration in the reference gas you will get no signal. If the background
concentration is higher than the reference you will even get a negative signal
(i.e. signal appears when reference gas is removed).
When using a reference leak the problem is less pronounced as the leak adds
gas to the background. The calibration will however be significantly affected if
background is higher than the resulting concentration added by the leak.
Calibrating in a high background will, however, always result in making the
detector more sensitive. This means quality is not affected. Some “good” prod-
ucts may be rejected but no bad products will be passed.
On the following page are detailed instructions for testing the sensor with 10
ppm Reference Gas.
Using Reference Gas
1. Preparing the Reference Gas
a. Check the reference gas type ( must be 10 ppm Hydrogen in synthetic
air)
b. Connect pressure regulator to the gas bottle. IMPORTANT! Never use a
regulator that has previously been used for the 5% tracer gas. This may
contaminate the reference gas bottle and alter the concentration!
c. Connect a hose to the gas regulator complete with mouthpiece or a
piece of 11-15 mm inner diameter hose to slide over probe tip.