ELECTRONIC SENSORS
electronics, industrial automation, data centre storage systems, automotive and many others. They exhibit lower accuracy than RTDs, are susceptible to system noise and often require calibration to ensure consistent readings between different devices.
Digital temperature sensors are integrated circuits (ICs) that measure temperature and provide a direct digital output, typically over communication protocols like SMBus, I²C, SPI, or 1-Wire. They don’t require the external signal digital conversion of the analog options.
Selection guidelines
Choosing the appropriate temperature sensor involves balancing accuracy, response time, durability and cost. Industry- selection of a suitable component. The operating environment of the application plays a crucial role. Harsh conditions necessitate robust sensors like thermocouples or coated RTDs, while thermistors or semiconductor sensors are more suitable for controlled environments. Cost and scalability are also factors to consider in mass production, thermistors are economical, but RTDs and high-end thermocouples offer long-term stability. The designer’s tolerance between accuracy versus practicality can also impact selection. RTDs provide high precision but are expensive, while thermocouples are more versatile but less accurate. Response time and placement also matter. Small, low-mass sensors like thermocouples and thermistors respond quickly, but their placement can impact performance.
The cost of a sensor and its associated especially in consumer products or high-volume manufacturing. There is a considerable cost range among sensor types. Analog sensors require signal conditioning, while digital sensors simplify integration. Reducing analog circuitry and calibration can minimise overall costs and justify the use of even a slightly more expensive digital sensor.
Digital options and characteristics Digital sensors convert an analog signal internally and transmit data as a digital stream, often providing better noise immunity and enabling more complex data processing. Analog Devices (ADI) offers a broad portfolio of analog and digital temperature sensors, and designers should carefully evaluate which best matches the needs of
Figure 3: An application circuit using a MAX31875 digital temperature sensor. (Image source: Analog Devices, Inc.)
their application. Following is a brief recap of some digital sensors.
When exact temperature readings are necessary, accuracy is likely the top selection factor. ADI’s MAX31888 digital sensor features ±0.25°C accuracy over a range of -20°C to +105°C, and communicates with a microcontroller over a 1-Wire bus to enable high-precision temperature monitoring circuits (Figure 1). Programmed into each MAX31888 is its own unique 64-bit registration number, which acts as the node address in a multi-drop 1-Wire network. The MAX31888 utilizes just one data line for communication, from which it can directly draw parasitic power, allowing designers to do without an external supply. When using external power supplies, its voltage range is from 1.7 V to 3.6 V while consuming only 68 μA of current during measurement. Power consumption and size may be the top concern when designing small, battery-operated devices. For applications such as wearables, ADI’s MAX31875 devices, such as the MAX31875R0TZS+T (Figure 2), combine a very small package size of 0.84
mm x 0.84 mm x 0.35 mm and low supply current consumption with a temperature measurement accuracy of ±1°C. The MAX31875 family uses an I2
C/SMBus-
compatible serial interface that uses standard write byte, read byte, send byte and receive byte commands to read behaviour in a typical circuit (Figure 3). It uses <10 μA average power supply current and can measure temperatures from -50°C to +150°C.
ADI also offers ICs designed to precisely measure the temperature of thermal diodes and convert it into a digital format, replacing conventional thermistors or thermocouples. These remote diode sensors measure the temperature of external PN junctions, like the thermal diodes built into CPUs, GPUs, FPGAs, and ASICs. The MAX6654MEE+T measures one thermal diode. Other options are available for 2, 3, 4, and 8-channel applications. Remote diode sensors can be widely employed in electrically noisy environments with appropriate internal and external MAX31732ATG+T is a 4-channel temperature sensor that monitors its own temperature along with the temperatures of up to four external diode-connected transistors (Figure 4).
The MAX31732 sensor can be programmed to set temperature thresholds without serial interface can be used to monitor temperatures and revise temperature thresholds.
Conclusion
Figure 4: ADI’s MAX31732 can monitor up to four external diode-connected transistors as in this application circuit. (Image source: Analog Devices, Inc.)
Finding the optimal temperature sensor can ensure better performance, reliability, Selection can be impacted by a range requirements and standards, and cost- versus-performance trade-offs. ADI’s digital temperature sensor portfolio offers solutions to meet the needs of a wide variety of applications.
SEPTEMBER 2025 | ELECTRONICS TODAY 19
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