Jerry Horn and Gordon Gleason
Lynium

There are many different types of sensors whose underlying realization is based on a Wheatstone bridge. Strain gauges are one such sensor. As a material is strained, there is a corresponding change in resistance. In many cases, each side of the Wheatstone bridge may respond to the strain by lowering or increasing in resistance.

This application note will focus specifically on load cells, a type of strain gauge that is typically used for measuring weight. Even more specifically, the focus will be on fully active, temperature compensated load cells whose change in differential output voltage with a rated load is 2 mV to 4 mV per volt of excitation (the excitation voltage being the difference between the +Input and the "Input terminals of the load cell). The goal is to develop a variety of circuits that can quantify this change via an analog-to-digital converter (ADC), which will be a MCP3551, 22-bit Delta-Sigma ADC.