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SERVICE INFORMATION
SERVICE INFORMATION
WARNING
All service information is intended for qualified
electronic maintenance personnel only.
NOTE: Instruments with the rev. number mentioned below or greater
conforms to ITS-90 thermocouple and RTD tables.
Model
Software Rev. Software Rev.
(Thermocouple) (RTD)
840A
6.10
NA
845
3.10
NA
850
5.10
5.11
855
4.20
4.22
(Software revision is marked on a label attached to integrated-circuit U1 on the mother-board.)
1. CALIBRATION PROCEDURES
This is a two-part procedure. Products with thermocouple functions only, follow the
Thermocouple Calibration procedure below. Products with resistance functions (RTD, thermistor,
ohms) follow first the Thermocouple Calibration procedure, then the Resistance Calibration
procedure.
A. THERMOCOUPLE CALIBRATION Test
Equipment Required:
1. Thermocouple simulator (Ectron 1120, or equivalent) calibrated to ITS-90.
2. Microvolt DMM (Fluke 8840A, or equivalent)
3. Calibration cables, per Figures 11, 12, 13.
NOTE: The copper constantan cables used in Figures 12 and 13 need to be
calibrated. Voltage errors in these cables should be compensated at the
simulator.
4. Calibration cover (820-307-4).
Ambient Conditions:
Units should be calibrated at an ambient temperature of 23°C ±1°C, with relative humidity less
than 80%.