For years, the sensor products industry has been primarily analog focused. Sensors operated using analog circuits and components, due in part to the analog front ends found in almost all electronic measurement devices. Analog sensors have been fairly straightforward devices, sometimes providing basic analog outputs, and in some cases adding amplification or gain, and signal conditioning before the output is sent to a measurement or control system. Today, these systems are becoming more sophisticated, and as a result, demand additional signal processing to achieve the desired system performance.
In the past, sensor system engineers were reluctant to move to digital products due to the challenges presented by adding digitization to existing analog sensor signal paths. The R&D costs of making these changes were out of reach for many small sensor companies that focused on single product types, applications, and markets. Over the past couple decades, a few digital sensors have entered the market, but the lack of any standard interface or communication protocols made the effort expensive and risky. Needless to say, digital adoption was slow.
Due to the increased availability of low cost electronic components that can process and convert analog signals to digital formats, the migration of analog sensors into the digital world is now underway in earnest. Over the past few years, sensor manufacturers have been starting to integrate sensor elements, A/D conversion, processing capability, memory, power management, and digital communications capability into just a few chips that easily fit into the sensor package. In addition, the proliferation of standard communication protocols like I2C and SPI have made it easy to integrate sensors fitted with these capabilities into electronic monitoring and control systems.
The digitization of sensor products has benefits far beyond the ability to easily communicate with digital control systems. As an example, most digital sensors include a “sleep mode” feature that turns the sensor off when it’s not needed for system functions. By reducing the power required, the battery life improves for remote and mobile systems that rely on energy harvesting or battery power. Digital sensors can also take advantage of software optimization routines that are not available in the analog mode. Techniques like oversampling and digital filtering can dramatically improve sensor resolution and frequency discrimination. Best of all, these performance improvements come with no cost increase. It’s all in the software.
There are a number of more subtle benefits that come with digital sensor products. Because a digital sensor has on-board memory, information can be stored. Nonvolatile information such as the device part number, revision level, serial number, and calibration factors can be included and easily accessed. Dynamic information such as number of interrogations, error logs, and hours of operation can be programmed in the senor software. This data can support a robust reliability and quality assurance program for the systems utilizing these sensors.
Digital sensor technology has enabled sensor manufacturers to create products that meet the unique needs of a customer’s system. Many digital sensor products today contain more than one sensing element. For example, a digital humidity sensor can also contain a temperature sensor, and by accessing the data from both and doing a little bit of math in the system host processor, the dew point can be generated. Three pieces of information are created (relative humidity, temperature, dew point) using the data from only two sensing elements, both in the same low cost sensor package.
Today’s complex systems are driven by the demand for “smart” capabilities. This has increased the need for additional digital sensors in system designs. Systems and products require more information to increase their capabilities. Products are required to be aware of their surrounding environment, its own health and uptime, received human inputs as well as other system interaction, all of which require the use of additional sensors. These sensors send that critical data to the microcontrollers through seamless interfaces, enabling them to make decisions based on the data received from the sensors. The more data provided, the more intelligent the decisions. Smarter systems require more sensors.
Digital sensors are now able to provide low cost solutions with increased performance and capability. The migration to digital sensors has enabled smarter systems by providing better performance, all while being built and integrated at very attractive price points and meeting customer design requirements.
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