Datasheet LT1031, LH0070 (Analog Devices) - 9

LT1031/LH0070
U APPLICATIO CIRCUITS Strain Gauge Conditioner for 350
Ω
Bridge
R1 357Ω 1/2W 28mA LT1031 28.5mA 15V IN OUT 5V 350Ω STRAIN GND R3 GUAGE BRIDGE** 2MΩ R2 20k 3 2 – + 6 6 V LM301A† R4 OUT • 100 LT1012C 2 20k 3 + 1 – 100pF R5 8 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 UL ** TRA 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 VIR † TUALLY ELIMINATED BY DIFERENTIAL CONNECTION OF LT1012C LT1031 • AC05
Ultralinear Platinum Temperature Sensor*
LT1031 OUT IN 20V GND R2* 5k R1** 253k R14 R10 5k 182k 1% R11 6.65M R15 1% 10k R8 Rf** 10M 654k R9 R12 100k 1k R13 20V 24.3k R5 2 R3** R4 – 7 200k 6 V 5k 4.75k 1% OUT = 100mV/°C LT1001 1% –50°C ≤ T ≤ 150°C 3 + 4 R † S –15V 100Ω AT 0°C R6 ST † ANDARD INDUSTRIAL 100Ω PLATINUM 4-WIRE SENSOR, ROSEMOUNT 78S, 619k OR EQUIVALENT. α = 0.00385 1% R7 TRIM R9 FOR VOUT = 0 AT 0°C 392k TRIM R12 FOR VOUT = 10V AT 100°C 1% TRIM R14 FOR VOUT = 5V AT 50°C USE TRIM SEQUENCE AS SHOWN. TRIMS ARE NON-INTERACTIVE SO THAT ONLY ONE –15V 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