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mV Pressure Sensor Signal Conditioning Circuit Design

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Pressure Sensor Signal Conditioning & Amplification Circuit Design

This document details a signal conditioning circuit designed for piezoresistive pressure sensors (such as the GZP160 series) featuring zero-point outputs from -5 mV to +10 mV and full-scale outputs from 60 mV to 100 mV. Operating on a single +3.3V supply, the architecture integrates a +0.206 V DC bias network to eliminate negative clipping at the low end and preserves a 13% engineering safety margin for ADC sampling.

1. Complete Schematic Diagram (Horizontal Layout)

=====================================================================================================
Excitation Buffer (U1A) ──► Sensor Unit (XGZP) ──► Stage 1: InAmp (U1B/U1C) ──► Stage 2: Bias Adder (U1D)           =====================================================================================================
2 1

2. Bill of Materials (BOM)

Designator

Value / Part Number

Tolerance / Forfait

Primary Function & Role

U1 (U1A~U1D)

LMV324 / LM324

SOIC-14

Quad operational amplifier (Rail-to-Rail output recommended)

R_F1, R_F2

47 kΩ

0603, 1%

Feedback resistors for the 1st stage instrumentation amplifier

R_G

1.8 kΩ

0603, 1%

Gain setting resistor (1st stage gain A_v1 ≈ 53.2x)

R1, R2, R_FB

10 kΩ

0603, 1%

2nd stage differential-to-single-ended network (Gain A_v2 = 1x)

R_BIAS1

15 kΩ

0603, 1%

Pull-up resistor for DC bias network (shifts offset to +0.206 V)

R_BIAS2

1 kΩ

0603, 1%

Pull-down resistor for DC bias network

R_REF1

10 kΩ

0603, 1%

Excitation divider pull-up resistor

R_REF2

680 Oh

0603, 1%

Excitation divider pull-down resistor (~0.21 V output)

C_FB

1 nF

0603, NPO

First-order low-pass filter capacitor (Cutoff frequency ~15.9 kHz)

C_DEC1, C_DEC2

100 nF / 10 µF

0603 / 0805

High-frequency and low-frequency power supply decoupling capacitors

3. Key System Parameters & Calculations

  • Total Circuit Gain: Approximately 2x
  • DC Offset Bias: +0.206 V
  • Input to Output Mapping Table:
    • -5 mV Input (Negative extreme offset) ──► ~0.05 V Output (Kept safely within ADC linear range, no negative clipping).
    • 0 mV Input (Nominal zero point) ──► ~0.206 V Output.
    • +10 mV Input (Positive extreme offset) ──► ~0.74 V Output.
    • +100 mV Input (Full-scale maximum) ──► ~2.87 V Output (Leaves a 13% headroom under +3.3V to prevent ADC saturation).
  • MCU Compatibility: Fully compatible with 3.3V/5V microcontroller ADCs (par exemple., STM32, ESP32, Arduino).

※ If you need amplified circuit design proposal, please contact Sencoch.