LumaSense Technologies INNOVA 1412i - Manual (Page 32)

Chapter 4
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BE6025-15 1412i Photoacoustic Gas Monitor LumaSense Technologies A/S
Page 32 of 202
The Monitor is an extremely versatile measuring instrument, which
can be used to perform almost any kind of monitoring task. Its
versatility may appear overwhelming at first, but to avoid such a
reaction, we suggest that you read this chapter thoroughly, and
follow the practical exercises, which are included. These exercises
give you a “guided tour” through a number of different practical
procedures – monitoring task; performance of a monitoring task;
scrolling through data after completion of a monitoring task. By
following these different procedures the Monitor operating philosophy
will become apparent and you will be able to quickly familiarise
yourself with its operation and control.
4.1 Special Terminology
Certain terms are used to describe the operation of the Monitor and
it is necessary to fully understand what these terms mean before you
start any practical exercise with the Monitor.
4.1.1 Measurement Cycle
A description of a measurement cycle is given on page 2 of the
Product Data Sheet (see boxed-in text and schematic diagram of the
measurement system of the Monitor). “Measurement Cycle” is the
term used to describe everything that takes place in the Monitor from
the time the pump starts to flush out the “old” gas sample in its
analysis cell, until the signal in the measurement chamber has been
measured using the last relevant optical filter.
The time taken to complete a measurement cycle is dependent upon
the following factors:
How many gases/vapours are being measured – this affects the
number of optical filters which need to be used.
The sample integration time selected – longer measurement times
provide greater accuracy.
The flushing times selected for the measurement chamber and the
tube as well as the length of the sampling tube attached to the
Monitor’s air-inlet – the longer the tube, the more time is needed to
flush it out between measurement cycles.
The cleanliness of air-filters which filter the air drawn into the cell
(this affects the pumping time required to draw a fresh air sample
into the analysis cell).
The degree of fluctuation in the concentration of the various gases
measured in consecutive measurement cycles (this affects the time
required to adjust the gain of the amplifier attached to the
microphones).