Thermo Scientific 49i Instruction Manual page 219

Thermo Fisher Scientific
Note An error in the zero setting of the pressure transducer does not
introduce a measurable error in the output concentration reading.
Therefore, if only a barometer is available and not a vacuum pump, only
adjust the span setting.
A rough check of the pressure accuracy can be made by obtaining the
current barometric pressure from the local weather station or airport and
comparing it to the pressure reading. However, since these pressures are
usually corrected to sea level, it may be necessary to correct the reading to
local pressure by subtracting 0.027 mm Hg per foot of altitude.
Do not try to calibrate the pressure transducer unless the pressure is known
accurately.
1. Remove the cover.
2. Disconnect the tubing from the pressure transducer and connect a
vacuum pump known to produce a vacuum less than 1 mm Hg.
3. From the Main Menu, press
to scroll to Pressure Calibration > and press
The Pressure Sensor Cal screen appears.
Note If Service is not displayed, refer to
page 7-4, then return to the beginning of this step.
4. At the Pressure Sensor Cal screen, press
The Calibrate Pressure Zero screen appears.
5. Wait at least 10 seconds for the zero reading to stabilize, then press
to save the zero pressure value.
6. Disconnect the pump from the pressure transducer.
7. Press to return to the Pressure Sensor Cal screen.
Pressure Transducer Calibration
to scroll to Service > press
""Accessing the Service Mode"
to select Zero.
Model 49i Instruction Manual
Servicing
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