ELECTRONIC SENSORS
Matching temperature sensor factors to application needs
Choosing the optimal temperature sensor for an application can be challenging, given the variety of sensor technologies available and the diverse industry requirements. However, many applications require exact readings, so it is essential to examine the wide range of options that are available. By Pete Bartolik
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electing a temperature sensor involves balancing multiple factors to meet design requirements, such as accuracy, response time, communication protocol, environmental robustness, power usage, cost and system integration. Sensors generally fall within four analog voltage digital signal output: Thermocouples have a wide temperature range and durability, measuring from cryogenic temperatures to over +1,800°C. They are rugged and can withstand harsh environments and respond quickly to rapid temperature changes. But they’re less accurate and stable than other options and require signal conditioning. They are well-suited for heavy industry, such as steel and glass production, and in-home and commercial appliances with high heat. Resistance temperature detectors (RTDs) are highly accurate and stable. They’re ideal for industrial automation and process control where precision is crucial. RTDs are commonly used in the food and pharmaceutical industries for tight temperature control in processes like brewing, sterilization and frying. They provide accurate temperature measurements for HVAC systems, and in laboratory and medical equipment like incubators and analytical instruments. RTDs can be expensive compared to alternatives like thermocouples and are fragile due to their elements. They are often used with a precision measurement circuit that adds to design complexity and cost. Thermistors are temperature-dependent resistors made from semiconductors that
Figure 1: A typical application circuit using the MAX31888 temperature sensor. (Image source: Analog Devices, Inc.)
exhibit high sensitivity. Large resistance changes for small temperature shifts and high resolution. Small, fast and low- cost, thermistors are available in various sizes from tiny beads to larger probes.
Figure 2: Representation of the MAX- 31875R0TZS+T form factor. (Image source: Analog Devices, Inc.)
18 SEPTEMBER 2025 | ELECTRONICS FOR ENGINEERS
They excel in applications with limited temperature spans, typically between -50°C and 150°C. Thermistors are very and consumer electronics, where ambient or body temperature is relevant, as well as automotive applications, battery management systems, consumer However, their non-linear resistance curve requires conversion formulas or lookup tables to translate resistance to accurate temperature, and they may experience drift over time compared to RTDs. Diode-based temperature sensors provide fast response times and are smaller than the other three analog types. They can readily interface with a microcontroller, analog-to-digital converters circuits (ASICs). They are cost-effective with a limited temperature range of -55°C to +150°C, and are utilised in a wide range of applications spanning consumer
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