CIRCUIT060094

Single-supply strain gauge bridge amplifier circuit with MSP430 smart analog combo

CIRCUIT060094

Downloads

Overview

Some MSP430™ microcontrollers (MCUs) contain configurable integrated signal chain elements such as op-amps, DACs and programmable gain stages. These elements make up a peripheral called the smart analog combo (SAC). For information on the different types of SACs and how to leverage their configurable analog signal chain capabilities, visit MSP430 MCUs smart analog combo training. To get started with your design, download the strain gauge bridge amplifier circuit design files. A strain gauge is a sensor whose resistance varies with applied force. The change in resistance is directly proportional to how much strain the sensor is experiencing due to the force applied. This pressure sensing circuit uses a strain gauge placed in a bridge configuration to measure the variation in resistance. This design leverages all four of the built-in op-amp blocks (SACs) in the MSP430FR2355. Two SAC_L3 peripherals are configured in general-purpose mode to amplify a differential signal created by the change in resistance of a strain gauge while the other two are configured in DAC mode to supply the reference voltage (Vref) and the excitation voltage (Vex). By varying R10, a small differential voltage is created at the output of the Wheatstone bridge which is fed to the two SAC op-amp instrumentation amplifier inputs. The linearity of the instrumentation amplifier is based on the input common-mode and output-swing ranges of the MSP430 SAC op-amp, which can be found in the specification chart at the end of this document. The output of the second stage op-amp can be sampled directly by the on-board ADC or monitored by the onboard comparator for further processing inside the MCU.
Features
  • Input Vi difference (Vi1 - Vi2): V = -2.22 mV to 2.27 mV
  • Output: Vo = 0.1 V to 3.2 V
  • Supply:
    • Vcc = 3.3 V
    • Vee = 0 V
    • Vref = 1.65 V
  • Strain gauge resistance variation = 115 Ω to 125 Ω
  • Vcm = 1.34 V
  • Gain = 690 V/V

Downloads

Design tool

MSP430 Strain Gauge Bridge Amplifier Circuit Code Examples and SPICE Simulation (Rev. A) SLAC796A.ZIP (56KB)

Supported products & hardware

Supported products & hardware

MSP430 microcontrollers
MSP430FR2311 16-MHz integrated analog microcontroller with 3.75-KB FRAM, OpAmp, TIA, comparator w/DAC, 10-bit ADC MSP430FR2355 24-MHz 105-C integrated analog microcontroller with 32-KB FRAM, Op-Amps/PGAs, 12-bit DACs, 12-bit AD

Technical documentation

star
= Top documentation selected by TI
No results found. Please clear your search and try again.
View all 1
Type Title Date
* Circuit design Strain gauge bridge amplifier circuit with MSP430 smart analog combo (Rev. A) Mar. 06, 2020

Related design resources

Design tools & simulation

SIMULATION TOOL
PSPICE-FOR-TI PSpice® for TI design and simulation tool TINA-TI SPICE-based analog simulation program
CALCULATION TOOL
ANALOG-ENGINEER-CALC Analog engineer's calculator

Support & training

TI E2E™ forums with technical support from TI engineers

View all forum topics

Content is provided "as is" by TI and community contributors and does not constitute TI specifications. See terms of use.

If you have questions about quality, packaging or ordering TI products, see TI support.

Videos