LumaSense Technologies INNOVA 1316A-2 - Manual (Page 16)

Chapter 1
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BE6021-11 1316A-2 Multi Gas Monitor LumaSense Technologies A/S
Instruction Manual Page 16 of 97
1.4.6 The O
2
and NO Measurement
O
2
and NO gas concentration are measured using electrochemical
(fuel cell) sensors. A fuel cell sensor provides an electrical response
that is proportional to the concentration of the sample gas.
The NDIR Module sample-cell exhaust is directed to UA1372 manifold
for O
2
or O
2
/NO measurement. Sample gas is delivered to the O
2
and
NO sensors through this manifold. The O
2
sensor provides a linear
output of approximately 9 to 13 milli-volts that is proportional to the
Oxygen concentration in the sample. The NO sensor provides a linear
output of approximately 50 nano-amperes per ppm of nitric oxide
over the range of 0 to 5.000 ppm in the gas sample. A 3-volt lithium
battery is included on the NO sensor to retain bias voltage when
source power is not applied.
Both O
2
and NO sensor outputs are sent to an ADC converter that
provides digital values representing gas concentration. Gas
concentration is determined by comparing sensor output at
calibration with the output of the sample measurement.
By calibrating the system with known concentrations of Freon,
Carbon Dioxide and for the UA1372 option Oxygen and NO the
absolute concentration values can be calculated.
In normal practice ambient air is used as the reference gas for the
oxygen measurement as it contains a stable amount of oxygen –
20.95 % referenced to dry gas condition.