LM135-LM235-LM335,A
THERMOCOUPLE COLD JUNCTION COMPENSATION
(compensation for grounded thermocouple)
Thermo-
couple
+15V
4.7kΩ
200k
Ω
R2
10
kΩ
1%
1MΩ
1%
R3
377Ω
308Ω
293Ω
45.8Ω
Seebeck
Coefficient
52.3µV/
o
C
42.8µV/
o
C
o
40.8µV/ C
o
6.4µV/ C
J
T
K
S
R3*
1N4568
LM135
LM235
LM335
12kΩ
R1
10k
Ω
Thermocouple
Adjustments : compensates for both sensor
and resistor tolerances.
1. Short 1N4568.
2. Adjust R1 for SEEBECK coefficient times
ambient temperature (in degrees K) across
R3.
3. Short LM135 and adjust R2 for voltage
across R3 corresponding to thermocouple
type.
J 14.32mV
K 11.17mV
T 11.79mV
S 1.768mV
71.5kΩ
1%
-15V
* Select R3 for proper thermocouple type
SINGLE POWER SUPPLY COLD JUNCTION COMPENSATION
Thermo-
couple
J
T
K
S
Thermocouple
LM135
LM235
LM335
R1
10kΩ
R3*
+15V
R3
1.05kΩ
856Ω
816Ω
128Ω
R4
365Ω
315Ω
300Ω
46.3Ω
Seebeck
Coefficient
52.3µV/
o
C
42.8µV/ C
o
40.8µV/ C
o
6.4µV/ C
o
10kΩ
200kΩ
+15V
Adjustments :
1. Adjust R1 for the voltage across R3 equal
to the SEEBECK coefficient times ambient
temperature in degrees Kelvin.
2. Adjust R2 for voltage across R4 correspon-
ding to thermocouple.
J 14.32mV
K 11.17mV
T 11.79mV
S 1.768mV
200kΩ
1N4568
R2
10
kΩ
1MΩ
Output
R4*
* Select R3 and R4 for proper thermocouple
9/11
STMICROELECTRONICS [ STMICROELECTRONICS ]
