Appendix F: Pressure Correction - Teledyne 8800T Instruction Manual

Appendices

Appendix F: Pressure Correction

Sensor Pressure is used in the context that this is the pres-
sure inside the sampling chamber when performing the
measurement, i.e. it is the operating pressure of the sensor.
Gas Pressure is used in the context that this is the pressure at
which the dewpoint is to be calculated.
Pressure Correction is used in the context that the values
displayed signify the moisture content at some pressure (we
refer to this as the 'Gas Pressure') different from the pres-
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sure at the sensor. Note that PPM, LBS and G/M readings
are by definition unaffected by pressure correction because
only the pressure at the sensor affects their value. While °C
and °F are affected by pressure correction by reporting what
the dewpoint would be at the Gas Pressure when the dew-
point is what is measured at the pressure at the sensor. How-
ever, this also implies that whether pressure correction is
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applied or not the PPM, LBS and G/M readings are
affected by the setting of the sensor pressure.
The factory default settings are: 14.7psi for both sensor and
gas pressure and pressure correction disabled.
When Pressure correction is disabled all dewpoints are
computed by assuming that both Sensor and Gas Pressures
are 14.7psi.
As all Teledyne dewpoint meters, the 8800T is equipped with
the necessary software to perform pressure correction.
However, for the lack of space, the 8800T does not have a
Pressure Correct button. Therefore the user can not set or
enable Pressure Correction, this must be done at the factory.
Consult with your representative.
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