GasCheck
Operating Manual V2.4
13
Fig. 4.1
Location of the ZERO and SPAN adjustment potentiometers
2. The sensor should be
powered for at least 30 minutes
before
checking its calibration.
3. Detach both pipes from the sensor head and attach first the ZERO gas
source to one of the ports. Adjust the needle valve to provide approx.
0.5 l/min to the instrument and allow the instrument to settle (for at
least 1 minute) before checking its reading (the instrument reading
may kick when opening the gas line). If the reading is outside the
required specification, adjust the ZERO potentiometer on the detector
printed circuit board.
4. Repeat step 3 above with SPAN gas. Adjustment is achieved using
the SPAN potentiometer on the detector printed circuit board. For
maximum accuracy, the bottle concentration should be corrected for
pressure (see next page).
NOTE
For the diffusion version of the GasCheck with self-
referencing, in step 4 remove the rubber cup from the
calibration port and then attach zero gas. Remember to
refit the rubber cap to the calibration port at the end of
the procedure.
Always make adjustments with the ZERO gas first and
then with the SPAN gas.
Gas may also be safely connected to an instrument by transferring it from a
cylinder or a gas mixer using gas balloons. Separate balloon assemblies must
be used for zero and span gas and different balloons should be used for
different span gas mixtures.
NOTE
Balloons should be used only for calibration checking
but not for accurate calibration.
