TYPICAL APPLICATIONS
(Continued)
Micropower Thermocouple Cold Junction Compensator
V
+
LM334
2k
1%
18k
1M
1%
V
-
R
Adjustment Procedure
3V +
LITHIUM
AMS385-2.5
R2
R1
ZERO ADJ
100k
TC ADJ
500
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)
R2
Voltage
Voltage
(Ω) Across R1
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
+
THERMOCOUPLE
+
-
-
COLD JUNCTION
ISO THERMAL
WITH LM334
METER
J
T
K
S
523
432
412
63.4
Typical supply current 50µA
Precision 1µA to 1mA Current Sources
AMS385-2.5
AMS385-2.5
30V
C1
150pF
R1
68k
C1
150pF
2
-
LM312
7
6
4
R1
68k
2
-
LM312
7
6
4
I
OUT
*
1.5V TO 27V
3
+
3
I
OUT
*
-1.5V TO -27V
+
R2
R2
-30V
*I
OUT
=2.5V/R2
5
Advanced Monolithic Systems
http://www.ams-semitech.com
AMS [ Advanced Monolithic Systems Ltd ]
