A Sensor Module for Structural Health Monitoring

A Sensor Module for Structural Health Monitoring

A sensor module is a small electronic device which provides a platform for multiple sensors to communicate with each other. Sensor modules are used for a variety of purposes including monitoring air pollution levels in hard-to-reach places, warning governments of potential natural disasters, and reducing the risk of injuries or death in dangerous work environments.

The module consists of three main parts: a sensing unit, an analog-to-digital converter (ADC), and a microprocessor. The ADC converts the analog sensor readout into digital data that can be transmitted over a standard serial connection to a computer for processing and analysis. The ADC also stores the sensor readings in memory. The microprocessor runs special-purpose software that allows the sensor module to detect faults, monitor and report results.

This article discusses the design of a simple and low-cost wireless sensor module for structural health monitoring (SHM). The sensing unit is composed of a three-axis vibration and tilt sensor, which uses a single MEMS accelerometer e.g. MMA7361L, and signal conditioning circuits for both tilt and vibration parameters. The A/D converter and data formatting are implemented based on the microcontroller PIC16F873. The DC unit transmits the conditioned data over a radio (RF) transceiver to the control module for remote monitoring.

Sensor modules are often used in engineering systems to monitor the integrity and functionality (the "health") of engineering subsystems such as rocket engine test stands, aircraft, vehicles, bridges, power plants, oil rigs, and defense installations. A smart sensor module contains a sensor, sensor signal-conditioning circuitry, an analog-to-digital converter, data storage circuitry, and a microprocessor that runs special-purpose software and communicates with one or more external computers.

A typical sensor module can be seen in the block diagram below. The sensor signal is amplified by an amplifier and converted to a digital signal by the ADC, which is then stored in memory and available for communication with a host computer. The microprocessor can be connected to a local PC by an RS-232 cable, where the software is downloaded into the random-access memory of the microprocessor and debugged.

Once the microprocessor is up and running, it controls the sensor module by monitoring input signals from the ADC and from an external sensor, sending them to the appropriate output devices such as relays or LEDs. In some applications, the sensor module may also be able to monitor its own status using a built-in onboard red LED.

This project uses an Arduino Uno to demonstrate the capabilities of a sensor module. The board has two universal inputs on a pluggable terminal block that can be used for either analog or digital input/output, and the A and B signals are connected to the TOWER header signal P4/A4/DAC0 and P5/A5/DAC1. The C pin is in default configuration connected to ground GND, but can be disconnected to use it as an extra input by pulling up its zero-ohm resistor. A red LED lights up when the sensor is activated, showing that the module has detected a magnetic field.

Tags:display module | electronics module