Servicing
Pressure Transducer Calibration
Thermo Electron Corporation Model 48i Instruction Manual 7-21
6. Calibrate the pressure transducer. Refer to the “Pressure Transducer
Calibration” procedure that follows.
Pressure Transducer
Calibration
Use the following procedure to calibrate the pressure transducer.
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 attempt to calibrate the pressure transducer unless the pressure is
known accurately.
Equipment Required:
Vacuum pump
1. Turn instrument OFF, unplug the power cord, and 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
If the Service Mode is not displayed on the Main Menu, use the
following procedure to display it.
a. At the Main Menu, press to scroll to Instrument Controls >
press > to scroll to Service Mode > and press .
Equipment Damage Some internal components can be damaged by small
amounts of static electricity. A properly grounded antistatic wrist strap must
be worn while handling any internal component.
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