AMS285-2.5/AMS385-2.5
TYPICAL APPLICATIONS (Continued)
Micropower Thermocouple Cold Junction Compensator
V+
LM334
2k
1%
18k
1M
1%
R
Adjustment Procedure
V-
TC ADJ
500
ZERO ADJ
100k
+
3V
LITHIUM
1. Adjust TC ADJ pot until voltage across R1 equals Kelvin temperature
multiplied by the thermocouple Seebeck coefficient.
AMS385-2.5
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
(Ω) (Ω) Across R1
@ 25°C (mV)
R2
Voltage
Voltage
Across R2
(mV)
+
-
+
J
52.3
42.8
40.8
6.4
523 1.24k
432 1k
412 953Ω 12.17
63.4 150Ω 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 50µA
Precision 1µA to 1mA Current Sources
AMS385-2.5
30V
AMS385-2.5
C1
150pF
C1
150pF
R1
68k
R1
2
3
-
68k
7
2
3
-
6
7
LM312
6
LM312
4
+
4
+
IOUT*
R2
IOUT*
1.5V TO 27V
R2
-1.5V TO -27V
-30V
*IOUT =2.5V/R2
Advanced Monolithic Systems, Inc. www.advanced-monolithic.com Phone (925) 443-0722 Fax (925) 443-0723
AMS [ Advanced Monolithic Systems Ltd ]
