AD630AR
Analog Devices
The AD8221 gains the signal and an AD630AR synchronously demodulates the waveform.
Application NoteAnalog
Strain Gage Measurement Using AC Excitation
Application note for strain gage measurement using AC excitation to eliminate offset drift and 1/f noise using the AD8221 instrumentation amplifier and AD630 demodulator.
Overview
This document details a circuit design for bridge-based strain gage measurements that utilizes AC excitation to overcome common DC errors, including offset drift, 1/f noise, and line noise. The design employs an Analog Devices AD8221 instrumentation amplifier to gain the AC bridge signal, leveraging its high common-mode rejection ratio (CMRR) at frequency. The signal is then processed by an AD630AR balanced modulator/demodulator for synchronous demodulation. After passing through a low-pass filter, the system produces a precise DC output proportional to the strain while removing DC errors associated with the amplifier and detector.
Use Cases
- Precision load cell signal conditioning
- Industrial weight scales
- High-accuracy pressure sensor interfaces
- Sensor measurements in high DC noise environments
- Bridge sensor applications requiring low offset drift
Topics
Analog Devices
AD8221
AD630AR
strain gage
AC excitation
bridge measurement
instrumentation amplifier
synchronous demodulator
CMRR
offset drift
1/f noise
Referenced Parts
AD8221
Analog Devices
The AD8221 gains the signal and an AD630AR synchronously demodulates the waveform.