Universal Signal Conditioning for Smart and Multiple Sensor Systems

January 1, 2006 By: Edward Zdankiewicz, George Hsu, Joseph Miller Sensors

As the world becomes increasingly networked, digital, and mobile, there is a corresponding need for sensor signal-conditioning and signal-processing products that are smart, inexpensive, and easy to use, and that can reduce the development time of the devices they go into.

The SSP1492, designed for high-volume, battery-powered, consumer, and commercial applications, is a monolithic IC device that works directly with resistive, capacitive, inductive, voltage, and pulsed sensor elements

Because there has been no standard sensor application development environment and processing circuitry, sensor end users have had to become experts in the specific sensor technology they wish to use and start from scratch in developing solutions for each new application. Needless to say, this situation has been a hindrance. Developing ASICs for sensors is a moving target of cost vs. performance over time. Customers have come to expect increased functionality at lower costs. Sensor manufacturers and product developers have wrestled with these demands in the past, but can no longer afford to dedicate large amounts of time and resources to this non-core activity. Instead, they are turning to companies that make it their sole focus. To better understand what one such company has to offer, let's review the classical signal conditioning approach.

Classical Signal Conditioning

The most widely used sensor signal-conditioning technique is to combine an instrumentation amplifier (in amp) and an A/D converter (ADC), as shown in Figure 1. In contrast to a general-purpose operational amplifier (op amp), the in amp is characterized by low drift, common-mode rejection, and high input impedance. In amps have a balanced differential input, meaning that the output voltage is proportional to the difference between the input voltages. The differential inputs are compatible with sensors that are balanced, such as bridge-based sensors, or unbalanced, where the sensor is single-ended with a ground return.