AMS285-1.2/AMS385-1.2
TYPICAL APPLICATIONS
(Continued)
Micropower Thermocouple Cold Junction Compensator
V
+
LM334
2k
1%
5.1k
1M
1%
V
-
R
Adjustment Procedure
TC ADJ
500
MERCURY
+
CELL
1.345V
AMS385-1.2
ZERO ADJ
100k
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.
Thermocouple
Type
Seebeck
Coefficient
(mV/
°
C)
52.3
42.8
40.8
6.4
R1
(Ω )
Ω
R2
Voltage
Voltage
(Ω ) Across R1
Ω
Across R2
@
25°C (mV)
°
(mV)
1.24k
1k
953Ω
150Ω
15.60
12.77
12.17
1.908
14.32
11.78
11.17
1.766
R2
R1
+
THERMOCOUPLE
+
-
-
COLD JUNCTION
ISO THERMAL
WITH LM334
METER
J
T
K
S
523
432
408
63.4
Typical supply current 50µA
Precision 1µ A to 1mA Current Sources
µ
AMS385-1.2
AMS385-1.2
30V
C1
150pF
R1
100k
2
-
LM312
3
I
OUT
*
-1.5V TO -27V
-30V
+
4
I
OUT
*
R2
1.5V TO 27V
R2
C1
150pF
2
-
LM312
6
3
+
4
7
6
R1
100k
7
*I
OUT
=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 ]
