LumaSense Technologies INNOVA 1412i - Manual (Page 148)

Chapter 12
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BE6025-15 1412i Photoacoustic Gas Monitor LumaSense Technologies A/S
Page 148 of 202
· It allows you to have a visually check that there is a net flow of
gas out of the Teflon tube attached to it during the whole
calibration procedure. The “flow ball” can be seen to be bouncing
on the upward flow of air out of the meter.
If the pressure of the gas from the cylinder is too low at any time
then the “flow ball” will just remain seated at the bottom of its
tube. This condition must be avoided because atmospheric air will
be drawn into the Teflon tube system via the flow meter and
cause dilution of the calibration gas. This will affect the accuracy
of your calibration.
· It functions as an escape valve. When the pressure of the gas in
the tubing becomes greater than atmospheric pressure, gas flows
out to the atmosphere via the flow meter. This ensures that the
gas entering the analysis cell is as close to atmospheric pressure
as possible, and this prevents damage to the very sensitive
microphones in the analysis cell.
WARNING! The analysis cell of the monitor is equipped with
sensitive microphones, and therefore NO direct connection between
the Monitor’s air-inlet and the pressure-valve on a gas cylinder is
allowed. Under NO circumstances should the pressure of the air in
the analysis cell be allowed to exceed 0.1 bar above the ambient
pressure.
1. Attach the Teflon tubing to the Air Inlet Filter at the back of the
monitor. This is described in detail in section 4.2 .
2.
a. Connect the free-end of the length of tubing attached to the
air-inlet to one of the branches of the “Y”-piece (see
attachment point no. 1 in Fig.12.5 ).
b. Cut off another 1m length of Teflon tubing and connect one
of its ends to attachment point no. 2 of the “Y”-piece (see
Fig.12.5 ) and its other end to a flow-meter.
3. Connect a 1m length of tubing to attachment point no. 3 of the
“Y”-piece (see Fig.12.5 ).
12.4.1 Producing a Supply of Clean, Wet Air
When humidity-interference calibrations are performed, clean, wet
air is required. This can be produced in the following manner.
We suggest that you bubble zero-gas (e.g. pure nitrogen) through a
thermostatically-controlled water-bath to produce a supply of clean,
wet air to the Monitor during humidity-interference calibration of the
filters (see Fig. 12.7 ). Notice that the thermostatically-controlled