Nexisense Temperature Sensor Types: Comprehensive Guide from Principles to Selection

Temperature sensors are essential components in modern industry and daily life. They convert temperature changes into processable electrical signals, supporting applications from simple monitoring to complex control. With technological advances, sensor types have diversified, each with unique features. Nexisense, as a dedicated sensor brand, offers multiple types to meet different scenarios. This article systematically introduces common temperature sensor types, from definition to application, helping you understand and select appropriately.

Definition and Classification Overview

A temperature sensor is a device that detects temperature and converts it into a usable output signal. Based on material and characteristics, they are mainly classified as contact or non-contact. Contact sensors include thermocouples, resistance temperature detectors (RTDs), and thermistors; non-contact sensors primarily use infrared. By output type, they can be analog, digital, or logic output.

Different types suit different ranges and accuracy requirements. Selection should consider measurement environment, response speed, and cost. The Nexisense series covers mainstream types, ensuring compatibility and stability.

Thermocouple Temperature Sensors: Principles and Features

Thermocouples are based on the Seebeck effect: two different metals joined to form a closed loop generate a thermoelectric voltage when the junctions are at different temperatures. This voltage is proportional to the temperature difference and is converted to a temperature value by secondary instruments.

The structure is simple, typically two dissimilar metal wires welded at the measurement junction (hot end) with the other end as the reference (cold end requiring compensation). Common types include K (Nickel-Chromium/Nickel-Silicon), J, and T.

Advantages: wide temperature range (-200℃ to 1800℃), high tolerance to temperature and vibration, fast response, suitable for harsh environments. Limitations: lower accuracy (±1–2℃) and need for cold junction compensation.

Resistance Temperature Detectors (RTDs): Principles and Features

RTDs use the property that metal resistance changes with temperature, often platinum (e.g., PT100, 100Ω at 0℃). Resistance increases linearly, offering high accuracy.

Structure includes the sensing element, protective tube, and junction box. Nexisense PT100 products use thin-film or wire-wound processes to ensure stability.

Advantages: high accuracy (±0.1–0.5℃), linearity, and repeatability; suitable for medium to low temperatures (-200℃ to 650℃). Limitations: slower response and sensitive to vibration.

Thermistor Temperature Sensors: Principles and Features

Thermistors are mostly semiconductor materials, typically NTC (negative temperature coefficient), with resistance decreasing sharply as temperature rises. High variation rate gives high sensitivity.

Structure is compact, usually bead or thin-film encapsulated. Linearity is poor and requires calibration.

Advantages: very high sensitivity (resistance change multiples), low cost, fast response; suitable for narrow-range high-precision measurements (e.g., room temperature). Limitations: strong nonlinearity, poor interchangeability.

Digital and Non-Contact Temperature Sensors

Digital sensors integrate silicon technology, such as DS18B20, using PTAT structures to directly output digital signals (e.g., 1-Wire protocol). Advantages: strong anti-interference, easy integration, multi-point measurement, ±0.5℃ accuracy.

Non-contact sensors mainly use infrared, detecting object radiation without contact. Suitable for moving objects or high-pressure environments, very fast response, but influenced by emissivity and distance.

Application Scenarios

Thermocouples: high-temperature furnaces, engines; RTDs: precise process control in pharmaceuticals, food; thermistors: home appliances, medical thermometers; digital: IoT multi-point monitoring; infrared: non-contact applications like steel rolling or body temperature measurement.

Nexisense products cover these scenarios, offering custom protective tubes and interfaces.

Measurement and Selection Guidelines

For contact sensors, fully immerse in the medium to avoid heat loss; for non-contact sensors, adjust field of view and emissivity.

Selection considerations: compatibility with medium (e.g., PTFE coating for corrosive environments); outdoor use requires protective housing; high-pressure pipes require pressure-resistant tubes. Balance range, accuracy, response speed, and cost.

Maintenance Guide

Regularly clean probes to avoid residue; calibration cycle depends on required accuracy (6–12 months); inspect cables to prevent oxidation. Store in a dry, ventilated place. Proper maintenance ensures long-term stability.

Technical Parameters Comparison

Thermocouple: wide range, response<1s, accuracy ±1.5℃; RTD: medium range, response 5–30s, accuracy ±0.15℃; Thermistor: narrow range, response <1s, accuracy ±0.1℃; Digital: -55℃ to 125℃, accuracy ±0.5℃; Infrared: -50℃ to 3000℃, millisecond response, accuracy ±1%.

FAQs

How to choose between thermocouple and RTD?
Thermocouples for high-temperature rough measurements, RTDs for precise medium-temperature measurements.

Why are digital sensors more resistant to interference?
Direct digital output reduces noise from analog transmission.

Is non-contact measurement accurate?
Depends on surface emissivity calibration, suitable for uniform materials.

What to consider for outdoor use?
Add protective housing, shield from sun and rain.

How many wiring options for PT100?
Two-wire, three-wire, four-wire; three-wire is most common to compensate lead resistance.

Conclusion

Temperature sensors come in various types, each with its strengths. From thermocouples' high-temperature tolerance to digital sensors' easy integration, choosing the right type directly affects measurement results. Nexisense provides reliable products for various applications. By understanding principles and selection considerations, you can optimize system performance and improve industrial process precision and efficiency. In a rapidly evolving technology era, mastering this knowledge helps make informed decisions for projects.