Appendix B Theory Of Operation - Michell Instruments XZR200 User Manual

XZR200 User's Manual
Appendix B Theory of Operation
The sensor employs a well proven, small Zirconium Dioxide based element at its heart
that does not require a reference gas. This removes limitations in the environments
in which the sensor can be operated with high temperatures, humidity and oxygen
pressures all possible.
Background Physics:
The partial pressure is defi ned as the pressure of a single gas component in a mixture
of gases. It corresponds to the total pressure which the single gas component would
exert if it alone occupied the whole volume.
Dalton's Law:
The total pressure ( ptotal ) of a mixture of ideal gases is equal to the sum of the partial
pressures ( pi ) of the individual gases in that mixture.
Σ
P total =
i = 1
From the equation above it can be derived that the ratio of the number of particles
( ni ) of an individual gas component to the total number of particles ( ntotal ) of the gas
mixture equals the ratio of the partial pressure ( pi ) of the individual gas component to
the total pressure ( ptotal ) of the gas mixture.
n
i
=
n
total
ni
ntotal
pi
ptotal
Michell Instruments
k
P i
P i
P total
Number of particles in gas i
Total number of particles
Partial pressure of gas i
Total pressure
APPENDIX B
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