Temperature sensors are devices used in industrial or commercial applications that measure the temperature of an environment or system. Wireless sensors relay this measurement over a network to a computing station or user interface. These sensors are used for continuous monitoring and can send real-time alerts if the measurements fall outside acceptable parameters. The global temperature sensor market is expected to be worth over $10 billion by 2026.
By Jordan McDowell
Temperature sensors come in many forms and designs. A thermometer is the most basic form of a temperature measurement device. Other common types of sensors include:
● Thermocouples: These are the most commonly used type of temperature sensors. Thermocouples are usually self-powered, can operate over a wide range of temperatures, and have speedy response times. Typically, a thermocouple will only specify the difference between the hot and cold ends of a metal wire, and it’s usually paired with another sensor to measure the temperature value.
● Resistance Temperature Detector (RTD): The resistance offered by a metal changes with its temperature. RTDs are based on this difference in resistance. The most common metals used for RTDs are nickel and platinum.
● Thermistors: These are similar to RTDs in that temperature changes create measurable changes in resistance. Thermistors are usually made of polymer or ceramic material. The Negative Temperature Coefficient (NTC) is the most commonly used type of thermistor. By and large, thermistors are cheaper than RTDs but less accurate as well.
It’s important to bear in mind the differences between these types. Sensors have a number of generic characteristics (such as linearity, sensitivity, and cloud-based monitoring), but different types of sensors have different requirements that not all environments will support. For instance, thermocouples don’t require a trigger, but they do need cold-junction compensation. This will affect the applications you can use that sensor for.
Important Features of Temperature Sensors
When selecting a sensor or manufacturer, it’s important to understand how versatile their products are. Many temperature monitoring features are common among most brands, but some are very selectively offered and can transform reporting and environmental control. Some of these features include:
- Linearity
In an ideal world, a sensor would have a perfectly linear response, i.e. a unit change in temperature creates a unit change in voltage output. In practice, however, sensors aren't perfectly linear. NTC thermistors tend to be exponentially non-linear, exhibiting significantly higher sensitivity at low temperatures than they do at high temperatures.
- Temperature Range
A sensor’s temperature range specifies the applications and temperatures at which it operates safely and accurately. A thermocouple sensor will have a set temperature range based on the materials it’s built from. With RTDs, you get a smaller temperature range but better accuracy and linearity. Thermistors offer the lowest temperature but outstanding sensitivity.
- Response Time
Response time is how quickly a sensor reports temperature. It depends on the mass and size of the sensor element. Platinum wire-wound elements tend to be among the slowest in responding to temperature changes. Glass micro-beads are among the fastest.
- Automated Data Logging
The reporting system in your lab must be able to accurately record data from a number of different sensors. You need to consider how secure it is and whether it can be interfered with externally, as well as the level of technical support offered. This will determine activity uptime for you. It’s also worth finding out beforehand how many sensors and users the system can support in total.
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