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GENERAL
The Model 1140A is a self-aligning instrument. Once VOLTAGE ALIGNMENT and TERMINAL
ALIGNMENT have been performed, the instrument is ready for use. There are no potentiometers to
set or resistors or capacitors to select. Allow a 30 minute warm-up before performing the
alignment procedure.
EQUIPMENT REQUIRED
•
Ten-volt dc standard: Fluke Model 732B or equivalent. The uncertainty of the voltage
must be <75 µV (for a minimum test-accuracy ratio, TAR, of 4:1) and be within the range
of 9.9 V dc to 10.1 V dc.
•
Shorting bar or cable: Pomona Electronics Model 5145 or equivalent.
•
Null detector/microvoltmeter: Keithley Model 155 or equivalent. This unit must be
capable of resolving 1 µV dc.
•
Low-thermal cable, Pomona 1756-24 or equivalent.
•
Ice-point bath: Hart Model 9101 zero-point dry well or equivalent. A properly made and
maintained distilled-water ice bath can also be used. An uncertainty of 0.01°C is required.
•
Calibrated Type T thermocouple (24 AWG recommended) with its error at 26°C
known to the nearest tenth of a microvolt.
thermocouple. If copper wires are attached to the thermocouple, the copper ends should
be shorted together. The insulation on the thermocouple wire ends should be stripped
back approximately 0.4" (10 mm).
•
Optional: Cover to shield terminals from air flow, such as Ectron P/N 114-523-01.
•
For units with firmware version 4.40 and above, the following items from the
Procedure
are also needed during alignment:
•
Digital multimeter (DMM), Hewlett Packard Model 3458A (with Option 02) or
equivalent.
•
Four-wire Type E thermocouple (24 AWG recommended), calibrated at 26°C
known microvolt error and with bare-wire ends for alloy and copper wires.
B
provides a procedure to calibrate a thermocouple. The insulation on the
thermocouple wire ends should be stripped back approximately 0.4" (10 mm).
PRELIMINARY
Turn the power to the Model 1140A off, set the alignment switch (recessed in a square hole in the
bottom cover just to the rear of the KEYPAD) to the right to enable ALIGNMENT, and turn the
Model 1140A on.
3 See Footnote
5
in
Appendix
SECTION X
ALIGNMENT
10
B.
10-1
Appendix B
provides a procedure to calibrate a
3
, if any,
Calibration
3
with
Appendix
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