This technical seminar will focus on applications where physical parameters — temperature, light, weight — must be measured with precision. The presenters will survey commonly encountered circuit applications with an eye on the tricky issues that arise in all analog designs. Throughout these application topics, many useful design tools and design techniques will be introduced that will help you improve your designs!

Example Applications Include:

• Remote system supervision with voltage and current monitoring
• Thermocouples
• Multiplexed data acquisition systems — optimizing the signal chain for peak performance
• Bridge Sensor Measurement — focusing on the design issues common to many different sensor types

Topic Detials (Detailed Agenda)

This detailed technical seminar focuses on applications where physical parameters - temperature, light, weight - must be measured with precision. The focus is on commonly encountered circuit applications with an eye on the tricky issues that arise in all analog designs.

The first application touches on measuring many different physical phenomena from a remote location. Sensor characteristics are discussed, and signal conditioning for these sensor outputs to make them suitable for conversion to digital signals is detailed.

Second, a detailed look at thermocouples and how they work is offered. This common temperature-sensing element is widely used but often misunderstood by circuit designers. Removing the mysteries surrounding thermocouples and showing how their signals can be properly conditioned for use in measurement systems provides designers with real-world advice they can apply directly.

Data acquisition systems which have a number of inputs from different sensors or signal sources give rise to several approaches to tackling this problem. Should you use separate converters for each signal, or multiplex the signals into one? What issues arise from using delta-sigma converters in multiplexed systems? These questions are addressed and guidelines proposed for each of these scenarios.

Finally, sensors used in a bridge arrangement are common - for measuring temperature, pressure, and weight. The last application focuses on these bridge measurement systems and discusses interfacing with converters, what signal conditioning and filtering should be used, and ends with a detailed look at a reference design from TI which implements a high-precision weigh scale.

Throughout these application topics, sidebar discussions will be introduced, to look in more detail at useful tools and techniques to improve your designs. Simulating circuits with SPICE, designing active filters, considerations for driving successive-approximation (SAR) analog-to-digital converters are all discussed. Some important concerns with how printed circuit board layout affects precision are also considered.

This seminar was written by the applications staff of Texas Instruments. The authors are Russell Anderson, Michael Ashton, Rick Downs, and Thomas Kuehl.