LT1031_15 Datasheet, PDF (9/12 Pages) Linear Technology – Precision 10V Reference

LT1031/LH0070
APPLICATIO CIRCUITS
Strain Gauge Conditioner
for 350Ω Bridge
R1
357Ω
1/2W
LT1031
28mA
28.5mA
15V
IN
OUT
GND
+³
6
LM301A^†
1
–²
100pF ₈
5V
350Ω STRAIN
GUAGE BRIDGE**
R3
2MΩ
R2
20k
2
R4
6
LT1012C
V_OUT • 100
20k
3
R5
2M
R6
2MΩ*
–5V
*THIS RESISTOR PROVIDES POSITIVE FEEDBACK TO THE BRIDGE TO ELIMINATE
357Ω LOADING EFFECT OF THE AMPLIFIER. EFFECTIVE ZIN OF AMPLIFIER STAGE IS
1/2W ≥ 1MΩ. IF R2–R5 ARE CHANGED, SET R6 = R3
**BRIDGE IS ULTRA LINEAR WHEN ALL LEGS ARE ACTIVE, TWO IN COMPRESSION
–15V
AND TWO IN TENSION, OR WHEN ONE SIDE IS ACTIVE WITH ONE COMPRESSED
AND ONE TENSIONED LEG
†_{OFFSET AND DRIFT OF LM301A ARE VIRTUALLY ELIMINATED BY DIFERENTIAL}
CONNECTION OF LT1012C
LT1031 • AC05
R1**
253k
R8
R9
10M
100k
R3**
5k
R7
392k
1%
–15V
Ultralinear Platinum Temperature Sensor*
LT1031
OUT
IN 20V
GND
R2*
5k
R_S^†
100Ω
AT 0°C
R14
R10
5k
182k
1%
R11
6.65M
R15
1%
10k
R_f**
654k
R12
1k
R4
4.75k
1%
20V
R5
200k
2_–
7
1%
LT1001
3₊
4
–15V
R13
24.3k
6
V_OUT = 100mV/°C
–50°C ≤ T ≤ 150°C
R6
619k
1%
†_{STANDARD INDUSTRIAL 100Ω PLATINUM 4-WIRE SENSOR, ROSEMOUNT 78S,}
OR EQUIVALENT. α = 0.00385
TRIM R9 FOR V_OUT = 0 AT 0°C
TRIM R12 FOR V_OUT = 10V AT 100°C
TRIM R14 FOR V_OUT = 5V AT 50°C
USE TRIM SEQUENCE AS SHOWN. TRIMS ARE NON-INTERACTIVE SO THAT ONLY ONE
TRIM SEQUENCE IS NORMALLY REQUIRED.
*FEEDBACK LINEARIZES OUTPUT TO ±0.005°C FROM – 50°C TO 150°C
**WIREWOUND RESISTORS WITH LOW TC
LT1031 • AC06
1031fb
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