by Majeed Ahmad
Temperature sensors come in a number of mechanical, electrical and solid-state electronics forms and are widely used in industrial, consumer, medical, automotive and computing segments. Take the case of an engineer who is using an analog temperature sensor—a thermistor—to monitor a fish aquarium – a mature application with a predictable temperature range.
He shares his frustration with precision and lookup tables on the EDAboard.com forums while asking the fellow designers for help. For a start, a number of factors come into play while making a choice regarding temperature sensor, including resolution, temperature range and environmental considerations. However, calibration and thermal management are the key factors in robust operation of temperature sensors. Another forum post outlines the calibration pains while using traditional temperature sensor devices such as RTD and thermistor.
Temperature sensing in the IoT era
Now imagine a temperature sensor operating in the Internet of Things (IoT) environment where connectivity to the network and subsequently to the cloud is paramount. Add the IoT environment to this equation and you have a far more demanding set of tasks for the humble temperature sensor.
First and foremost, these sensors are bound to occupy a smaller footprint and consume very low power in order to boost the battery life for IoT applications. The autonomous nature of temperature sensor implies that it should draw extremely low energy for the IoT-centric applications like smart home.
Researchers at the Eindhoven University of Technology (TUE) have recently demonstrated a tiny wireless temperature sensor that weighs just 1.6 milligrams and is about the size of a grain of sand. More importantly, it comes with a built-in antenna capable of transmitting radio waves to power the chip, so it picks up energy as well as delivers wireless signals or data to the IoT gateway.
Interface and reliability issues
While IoT technology opens up new frontiers for sensors, it also demands a certain degree of intelligence from sensors so that they can filter useful signals from the large amounts of data they produce. In other words, sensors should be able to carry out signal processing to furnish the data for cloud processing.
The IoT bandwagon that brings a plethora of new applications for temperature sensors—data centers and IT server rooms, greenhouse monitoring, cold storage and refrigerated trucks, wine cellars, second homes, etc.—is clearly tilting the balance toward semiconductor-based temperature sensing devices.