A lot of media attention is generally focused on the latest gee-whiz processor advances and forecasts of their potential uses and market sizes. But the trend of older technologies coming down in price and thus creating new markets for themselves is sometimes even more exciting. As prices fall, new uses for old components emerge. One example of this trend is the increasing use of so-called “smart sensors,” which have on-board processing.
Being analog components, most sensors are prone to nonlinearities; they also exhibit offset and gain errors. At the outputs, sensors typically have limited dynamic range and high impedance, which make them susceptible to electrical noise as well. As a result, ordinary (dumb?) sensors typically require dedicated external circuitry for signal conditioning and to perform error compensation and filtering. If lots of data is generated in spurts, buffering too may be required.
Unlike their dumb brethren, smart sensors integrate the sensor along with the required buffering and conditioning circuitry in a single enclosure. Circuitry on-board the smart sensor usually consists of data converters, a processor and firmware, and some form of nonvolatile memory. Being processor-based devices, such sensors can be custom-programmed to satisfy specific system requirements and later reprogrammed as needed.
A smart sensor can be easily added to a piece of embedded hardware, say as a single chip or a daughtercard via a digital interface. Or, as is increasingly common in the field of remote data sensing, a wireless-equipped smart sensor can perform local processing of the raw data then ship the processed data up to a base station at regular intervals.
The benefits are tremendous. Vendor-supplied firmware on-board a smart sensor can automate the removal of nonlinearities and offset and gain errors from raw sensor readings, thus eliminating the need for custom post-processing at the main processor. The calibration data on a smart sensor can also be stored locally, in nonvolatile memory, so that the sensor module as a whole can be moved and reused without recalibration.
On-board data processing and local storage also make new capabilities at the sensor’s location, such as the ability to take action without intervention by the host processor. For example, a smart sensor could issue a quick early warning when measured parameters are approaching critical limits, or are changing at an abnormal rate. A sensor could even send a maintenance alert to the main system controller calling for replacement.
Even components as seemingly mundane as these can be made significantly more interesting with a little firmware. As the price of computing power drops, useful new applications for that power do indeed emerge.