Teledyne 7300a - NDIR analyzer - Manual (Page 69)

Infrared Gas Analyzer Operation 4
4-33 Teledyne Analytical Instruments
tivity of the binary gas, the analyzer would normally be set up so that the 100%
oxygen (0% argon) concentration would correspond to the zero level (4mA 0 V)
of the output signal. Then, 85% oxygen (15% argon) would correspond to
20mA (1 V) in the signal output.
It may be convenient for the user to have the outputs reversed so that the
85-100% oxygen level outputs a 4-20mA (0-1 V) signal respectively. This can
be accomplished by reversing the data input to the custom settings. Not all
applications will require a reversing function, however, if this is desirable. This
can be programmed by allowing the user to set the analyzer to read reversal
output. Contact the factory for further information.
4.9.1.2 Output Signal Offset
TAI has provided the output offset feature in the software for the accuracy
purpose. In many cases, the analyzer does not require this feature. For exmple,
if the analyzer has setup to analyze the sample gas of 40-50% CO
2
in nitrogen,
normally zero gas of this application requires 40% CO
2
in nitrogen. However,
100% of nitrogen can be used to zero the analyzer. In this case, the output
offset is not needed to setup. For linear output the accuracy will access success-
fully within +/-1% off. But, if the application is analyzing the sample gas that is
not linearly, the accuracy of the analyzer may not meet the specification. There-
fore, output offset is required and 40% CO
2
in nitrogen is also needed for zero
calibration gas.
To set up the output reversal or output offset, see section 4.8.1-set AP-
PLICATION sceen.
NOTE: If the inverting has been setup, “i” shall display on the left
bottom corner. Otherwise, the left bottom corner display ”n”.
NOTE: In the example 40% CO
2
in N
2
is discouraged, because it is
hard to produce the exact concentration.
4.9.2 Polarity Reversal
In some special applications, user will find that the display dispalys negative
concentration values, even if proper span gas is injected. To correct this
problem, TAI has added the Polarity Correction feature. This feature can be set
as follow:
Close S1-5 range 1
Close S1-6 range 2
Close S1-7 range 3
Close S1-8 cal range