LH0070 View Datasheet(PDF) - Linear Technology
Part Name
Description
Manufacturer
LH0070 Datasheet PDF : 12 Pages
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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
VOUT • 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
RS†
100Ω
AT 0°C
R14
R10
5k
182k
1%
R11
6.65M
R15
1%
10k
Rf**
654k
R12
1k
R4
4.75k
1%
20V
R5
200k
2–
7
1%
LT1001
3+
4
–15V
R13
24.3k
6
VOUT = 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 VOUT = 0 AT 0°C
TRIM R12 FOR VOUT = 10V AT 100°C
TRIM R14 FOR VOUT = 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
9
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