AMS285-1.2/AMS385-1.2
TYPICAL APPLICATIONS (Continued)
Micropower Thermocouple Cold Junction Compensator
V+
LM334
2k
1%
5.1k
1M
1%
R
Adjustment Procedure
V-
TC ADJ
500
MERCURY
CELL
ZERO ADJ
100k
+
1. Adjust TC ADJ pot until voltage across R1 equals Kelvin temperature
multiplied by the thermocouple Seebeck coefficient.
1.345V
AMS385-1.2
2. Adjust ZERO ADJ pot until voltage across R2 equals the thermocouple
Seebeck coefficient multiplied by 273.2.
R2
R1
Thermocouple
Type
Seebeck
Coefficient
(mV/ °C)
R1
R2
Voltage
Voltage
Across R2
(mV)
(W) (W) Across R1
@ 25°C (mV)
+
-
+
J
52.3
42.8
40.8
6.4
523 1.24k
432 1k
408 953W 12.17
63.4 150W 1.908
15.60
12.77
14.32
11.78
11.17
1.766
THERMOCOUPLE
METER
-
T
K
S
COLD JUNCTION
ISO THERMAL
WITH LM334
Typical supply current 50mA
Precision 1mA to 1mA Current Sources
AMS385-1.2
30V
AMS385-1.2
C1
150pF
C1
150pF
R1
100k
2
3
R1
-
7
100k
2
3
6
-
LM312
7
6
4
LM312
+
4
+
IOUT*
R2
1.5V TO 27V
IOUT*
R2
-1.5V TO -27V
-30V
*IOUT =1.23V/R2
Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
ADMOS [ ADVANCED MONOLITHIC SYSTEMS ]
