Directly from the manufacturer

Image
  1. Home
  2. Know How
  3. Temperature Meaurement
  4. Basics
  5. How temperature sensors work

Sensors: how they work

Temperature sensors

The choice of the right sensor determines the accuracy of the measurement result. However, there is no sensor that can do everything equally well:

  • A large measuring range generally means limited accuracy.

  • Particularly fast probes are usually not suitable for robust everyday measurements.

  • The design determines which probe is optimally suited for which measurement task.

Thermocouple sensors

Thermocouple sensor
  • Electrical voltage at measuring point / reference junction.

  • Measured value at reference junction is converted to 0 °C.

  • Sufficient equalisation time must be taken into account.

  • Operating principle: Seebeck effect – two different metals generate a temperature-dependent voltage.

  • Very large measuring range: −270 °C to over +1,370 °C.

  • Common types: Type K (NiCr-Ni), Type T (Cu-CuNi), Type J (Fe-CuNi).

Platinum resistance sensors

Platinum resistance sensor
  • Measuring principle: positive temperature coefficient effect of metals.

  • Relationship: temperature and electrical resistance.

  • Reference value at 0 °C: Pt100 = 100 Ω, Pt1000 = 1,000 Ω (wound platinum wire); measuring range −200 °C to +850 °C in each case.

  • Pt1000 less susceptible to interference with long lead wires.

  • High accuracy and long-term stability.

Thermistor sensors

Thermistor sensor
  • Temperature sensors based on mixed oxide ceramics.

  • Negative temperature coefficient: NTC.

  • Without reference junction compensation – ideal for refrigeration and freezer rooms.

  • Resistance decreases non-linearly as temperature rises – very high sensitivity.

  • Typical measuring range: −10 °C to +300 °C.

  • Cost-effective and compact, but with a limited measuring range.

Do you have questions or would you like personal advice? Contact us!

We look forward to supporting you with our expertise and individual solutions.

Testo - Head Office
Testo Pty Ltd
Unit 11, 114-118 Merrindale Drive
Croydon SouthVictoria 3136
Australia
+61 (0)3 8761 6108+61 (0)3 4100 0438
Testo - Service Centre
For all calibration and repair services.
Unit 1, 10-12 Sigma Drive
Croydon South Victoria 3136
Australia
+61 (0)3 8761 6108

You can reach us by telephone during these hours:

Mon - Fri: 9:00 - 17:00 (AEST)
Image
Blog

Visit our blog

© 2026