Servicing
Pressure Transducer Calibration
Thermo Fisher Scientific Model 49i Primary Standard Instruction Manual 6-33
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 Service > press >
to scroll to Pressure Calibration > and press .
The Pressure Sensor Cal screen appears.
Note If Service is not displayed, refer to ““Accessing the Service Mode” on
page 6-4, then return to the beginning of this step.
4. At the Pressure Sensor Cal screen, press to select Zero.
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.
8. At the Pressure Sensor Cal screen, press to select Span.
The Calibrate Pressure Span screen appears.
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