LT1025_15 Datasheet, PDF (1/12 Pages) Linear Technology – Micropower Thermocouple Cold Junction Compensator

LT1025
Micropower Thermocouple
Cold Junction Compensator
FEATURES
s _{80µA Supply Current}
s _{4V to 36V Operation}
s _{0.5°C Initial Accuracy (A Version)}
s _{Compatible with Standard Thermocouples}
(E, J, K, R, S, T)
s _{Auxiliary 10mV/°C Output}
s _{Available in 8-Lead PDIP and SO Packages}
U
APPLICATIO S
s _{Thermocouple Cold Junction Compensator}
s _{Centigrade Thermometer}
s _{Temperature Compensation Network}
DESCRIPTIO
The LT^®1025 is a micropower thermocouple cold junction
compensator for use with type E, J, K, R, S, and T
thermocouples. It utilizes wafer level and post-package
trimming to achieve 0.5°C initial accuracy. Special curvature
correction circuitry is used to match the “bow” found in all
thermocouples so that accurate cold junction compensation
is maintained over a wider temperature range.
The LT1025 will operate with a supply voltage from 4V to 36V.
Typical supply current is 80µA, resulting in less than 0.1°C
internal temperature rise for supply voltages under 10V.
A 10mV/°C output is available at low impedance, in addition
to the direct thermocouple voltages of 60.9µV/°C (E),
51.7µV/°C (J), 40.3µV/°C (K, T) and 5.95µV/°C (R, S). All
outputs are essentially independent of power supply voltage.
A special kit is available (LTK001) which contains an LT1025
and a custom tailored thermocouple amplifier. The amplifier
and compensator are matched to allow a much tighter specifi-
cation of temperature error than would be obtained by adding
the compensator and amplifier errors on a worst-case basis.
The amplifier from this kit is available separately as LTKA0x.
The LT1025 is available in either an 8-pin PDIP or 8-pin SO
package for temperatures between 0°C and 70°C.
, LTC and LT are registered trademarks of Linear Technology Corporation.
BLOCK DIAGRA
BOW*
CORRECTION
VOLTAGE
E 60.9µV/°C
V_IN
+
BUFFER
–
J 51.7µV/°C
K,T 40.6µV/°C
R, S 6µV/°C
10mV/°C
TEMPERATURE
SENSOR
R– COMMON
V₀ 10mV/°C
*CORRECTS FOR BOW
GND
IN COLD JUNCTION, NOT
IN PROBE (HOT JUNCTION)
LT1025 • BD01
TYPICAL APPLICATIO
Type K 10mV/°C Thermometer
R2
100Ω
FULL-SCALE TRIM
R3**
255k
1%
V⁺
V_{IN K}
LT1025
GND R^{– VO}
R1
1k
1%
–+
TYPE K
R4*
V^–
V⁺
–
LTKA0x^††
+
C2
0.1µF
V_OUT
10mV/°C
V^–
*R4
≤
V^–
30µA
,
R4
IS
NOT
REQUIRED
C1
(OPEN) FOR LT1025 TEMPERATURES ≥ 0°C
0.1µF ^{**SELECTED FOR 0°C TO 100°C RANGE}
†† _{OR EQUIVALENT. SEE}
“AMPLIFIER CONSIDERATIONS”
LT1025 • TA01
1025fb
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