How do Temperature Sensors Work?

Each temperature sensor style has its own set of operating principles, features, benefits, considerations, and limitations for optimal use.

Thermistors (NTCs and PTCs)

• Thermistors are thermally sensitive resistors whose prime function is to exhibit a large, predictable, and precise change in electrical resistance when subjected to a corresponding change in body temperature.
• Negative temperature coefficient (NTC) thermistors exhibit a decrease in electrical resistance when subjected to an increase in body temperature.
• Positive temperature coefficient (PTC) thermistors exhibit an increase in electrical resistance when subjected to an increase in body temperature.
• Based on the predictable characteristics and their excellent long-term stability, cost-effective thermistors are generally accepted to be the most advantageous sensor for many applications, including temperature measurement and control.

RTDs

• Platinum resistance temperature detectors (RTDs) are temperature sensors that have a positive, predictable, and nearly linear change in resistance when subjected to a corresponding change in their body temperature.
• The nearly linear output needed to precisely measure temperature over a very wide range makes RTDs ideal for more-specialized applications requiring very high accuracy (ex. 0.06 %/0.15 °C) or for applications requiring a lot of precision.

Digital Temperature Indicators

• Digital temperature indicators have a positive relationship between resistance and temperature. The response is very much like a digital signal; below the trip temperature, resistance will be low, above the trip temperature, resistance will be very high.
• This digital response is ideal for applications where knowing the temperature has increased beyond a specific value is required. With the digital response, no analog to digital conversion is necessary, allowing designers to save time and space.

Can I Customize Temperature Sensors?

Modifications are available to existing standard product packages, such as adding connectors or changing wire size or length, as well as offering special resistance-temperature (R-T) curves, R-T curve matching, and custom lead forming and bending to discrete thermistors. In addition, the following options and services are available.

• Complete custom sensor packages, including moisture resistant designs
• Custom resistance-temperature (R-T) characteristics
• Specialized resistance tolerance or temperature accuracy within specified temperature ranges
• Sensing element design for best long-term stability
• Rapid prototyping and quick-turn concept parts including 3D printed parts
• Prototype units using prototype tooling
• Reliability/validation testing options
• Fully designed, production-capable sensor and tooling

Typical Applications for Temperature Sensors

Temperature sensors are used in diverse markets.

HVAC/R

• Residential & Commercial Air Conditioning
• Chilled Water Systems
• Outdoor Temperature Sensors
• Instant Water Heaters
• Condenser, Evaporator & Duct Sensors

Renewable Energy

• Hydrogen Fuel Cell Sensors
• Battery Fuel Gauges
• Solar Panel
• Geothermal
• Battery Energy Storage Systems
• Solar Inverters

Appliances

• Oven Temperature Control
• Washing Machines
• Clothes Dryers
• Water Heaters
• Consumer Refrigerators/Freezers

Food Service

• Commercial Coffee Makers
• Hot/Cold Beverage Dispensers
• Food Thermometers
• Walk-in & Reach-in Refrigerators/Freezers
• Temperature Controlled Display Cases

Medical

• Blood Analysis Equipment
• Infant Incubators
• Skin Temperature Monitors
• Blood Dialysis Equipment
• Patient Warming