2002 by ELTRA GmbH Germany – January 2002 – Service Manual OH 900 / ON 900 / ONH 2000
2.9-1
2.9
2.9
Linearization:
The linearization of the analyser is done in the factory by the taking into operation and
does not need to be repeated by the customer.
You therefore have to be discouraged from experimenting with the linearity.
The following description is only advised if the number of channels is increased ( see
3.12), or if the range of a channel has to be changed ( for example by installing a longer or
shorter IR path).
The infrared cell is basically nonlinear; meaning that its output voltage is not proportional
to the CO2 concentration.
It is therefore necessary to correct this nonlinearity electronically, by means of the
software, in order to obtain accurate results.
The exact characteristic curve must be individually determined for each measurement
channel, and then fed into memory.
A so-called „linearity factor“ is transferred to the analyser, by means of its keyboard,
in order to determine the slope of the characteristic curve, ( see next pages ).
After feeding in a ( new ) factor, a high and a low standard sample are analyzed, to check
for accuracy.
If, after the test, the measurement results of the low standard sample are not correct, a
new linearity factor is fed in and the test is repeated.
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