LM185-2.5-N, LM285-2.5-N, LM385-2.5-N
SNVS743D –DECEMBER 1999–REVISED MARCH 2013
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Calibration
Calibration
1. Short LM385-2.5-N, adjust R3 for IOUT=temp at 1.8 μA/°K
1. Short LM385-2.5-N, adjust R3 for IOUT=temp at 1μA/°K.
2. Remove short, adjust R2 for correct reading in centigrade
2. Remove short, adjust R2 for correct reading in °F
Figure 20. 0°C–100°C Thermomemter
Figure 21. 0°F–50°F Thermomemter
Adjustment Procedure
1. Adjust TC ADJ pot until voltage across R1 equals Kelvin temperature multiplied by the thermocouple Seebeck
coefficient.
2. Adjust zero ADJ pot until voltage across R2 equals the thermocouple Seebeck coefficient multiplied by 273.2.
Figure 22. Micropower Thermocouple Cold Junction Compensator
Thermocouple Type(1)
Seebeck
Coefficient
(μV/°C)
R1
(Ω)
R2
(Ω)
Voltage Across R1
@25°C
Voltage Across R2
(mV)
(mV)
J
T
K
S
52.3
42.8
40.8
6.4
523
432
412
63.4
1.24k
1k
15.60
12.77
12.17
1.908
14.32
11.78
11.17
1.766
953Ω
150Ω
(1) Typical supply current 50 μA
8
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