RTD sensors

Resistance Temperature Detectors (RTDs)

Resistance Temperature Detectors are sensors that measure temperature by correlating the resistance of the RTD element with temperature. Most RTD elements consist of a length of fine coiled wire wrapped around a ceramic or glass core. The element is typically relatively fragile, so it is generally installed inside a sheath to protect it. The RTD element is constructed from a pure material, the resistance of which, at various temperatures, has been documented by various international standards institutes. The material has a predictable change in resistance as the temperature varies; it is this change that is used to determine temperature. RTDs are generally considered to be among the most accurate temperature sensors available.In addition to providing very good accuracy, they feature excellent stability and repeatability. RTDs also provide high immunity to electrical noise and are, therefore, well suited for applications in process and industrial automation environments, especially around motors, generators and other high voltage equipment.


NSPI manufactures an almost infinite variety of RTD sensors and assemblies, and most can be supplied in 48 hours or less. Options include combinations of different element materials, values and accuracies, a choice of element leadwire configurations, and a selection of sheath materials and diameters. Many of our RTD assemblies are supplied in drilled or flanged wells, and all assemblies can be supplied with our economical, head mount or DIN-rail mounted transmitters. If you can’t find a catalog RTD for your application, just contact us – custom versions can often be fabricated in less than a week!

Typical RTD applications

  • Furnaces
  • Microelectronics
  • Medical research
  • Textile production
  • Plastics processing
  • HVAC and refrigeration
  • Foodservice processing
  • Petrochemical processing
Data sheets
Model (PDF) Description
101, 102 & 103 General purpose
110 Field cuttable
120 Hand-breakable
201 & 203 RTDs with welded fittings
301 & 304 Spring loaded with explosion proof housing
302 & 303 Spring loaded without transmitter for general purpose housing
305 Spring loaded, 1/2″ NPT hex nipple
312 Spring loaded, 1/2″ NPT hex nipple
451 Direct immersion sanitary
452 Spring loaded sanitary temperature sensor
461 Sanitary RTD with removable sensing element
2543 Non-intrusive flow through sanitary sensor
3142B Sanitary flush mount tank temperature sensor
3226A Food piercing temperature sensor
3304A Flexible stick-on surface temperature sensor
3312A Autoclave temperature sensor
3332A Embedded temperature sensors for rotating machinery and turbines
Bearing temperature  Sensors for the measurement of bearing temperatures
Bayonet fitting design Spring loaded bayonet fitting temperature sensors
Flow computer/corrector RTDs  Temperature sensors for flow computers and gas correctors

Resistance vs Temperature Tables: Chart1 and Chart 2

RTD General Specifications

How to Size a Sensor