Servicing
Ambient Temperature Calibration
7-38 Model 42i Low Source Instruction Manual Thermo Electron Corporation
1. Remove the instrument cover.
2. Tape the thermistor (plugged into the measurement interface board) to a
calibrated thermometer (Figure 7-2).
Note Since the thermistors are interchangeable to an accuracy of ±0.2 °C,
and have a value of 10K ohms at 25 °C, an alternate procedure is to connect
an accurately known 10K resistor to the thermistor input (AMB TEMP) on
the measurement interface board, and enter the temperature reading.
A 1 °C change corresponds to a ±5% change in resistance, thus this
alternative procedure can be quite accurate as a check; however, it clearly is
not NIST traceable.
3. From the Main Menu, press to scroll to Service > press >
to scroll to Temperature Calibration > and press .
The Calibrate Ambient Temperature 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 .
The Service Mode screen appears.
b. Press to toggle the Service Mode to ON.
c. Press > to return to the Main Menu.
d. Continue the procedure at the beginning of Step 3 to access the
Calibrate Ambient Temperature screen.
4. Wait at least 10 seconds for the ambient reading to stabilize, use
and to enter the known temperature, and
press
to save the temperature value.
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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