Tegam 840A, Instruction Manual, Page: 32 / 40

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SERVICE INFORMATION
Table 6: Calibration of Calibrator-Mode Resistance Functions (RTD-Thermistor)
STEP SENSOR
SELECT
UNIT
OUTPUT
CURRENT
SOURCE INPUT
ADJUST VERIFY DMM READING*
1 RTD-100
1562.0 ° F
1mA P38 0.39048V
2 RTD-100
32.0 ° F
1mA √ 0.10000±0.00003V
3 RTD-100
-328.0 ° F
1mA √ 0.01852±0.000006V
4 1,000Ω 900.00Ω 1mA √ 0.90000±0.00020V
5 1,000Ω 1.00Ω 1mA √ 0.00100±0.00020V
6 100,000Ω 90,000Ω 10µA P51 0.90000V
7 100,000Ω 100Ω 10µA √ 0.00100±0.00020V
8 Thermistor
293.0 ° F
1mA √ 0.04700±0.00020V
9 Thermistor
77.0 ° F
10µA √ 0.02252±0.00020V
10 Thermistor
-40.0 ° F
10µA √ 0.75790±0.00500V
* exclusive of noise.
2. CALIBRATION VERIFICATION
Calibration is verified with the same instrument hookups as used for calibration (ie. Figures 12 and
13 for thermocouple functions, Figure 14 for resistance functions).
While one hookup serves to verify all resistance functions (RTD, thermistor, ohms), a full check-
out of thermocouple functions requires a set of calibration cables for each thermocouple type.
To simplify the verification of thermocouple calibration, software has been enhanced to reactivate
the copper-mode used during calibration. This feature is available on products that use the
following (and later) software revisions:
Model Software Revision
840A 6.7
845 3.7
850 5.6
855 4.16
(
Software revision is marked on a label attached to integrated-circuit U1 on the mother-board.)