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Temperature Reaction Time of Simple Hardware Devices


Several measuring points are generally used when determining the response time. Each of them is a time period in seconds required for the sensor reading/output to reach x% of the total value change (difference in temperature).

A single time period is known as sensor response time (or thermal response time).

Percentage Also used as Specific term
50% T50 or t0.5 none
63.2% T63 or t0.63 Sensor Time Constant (τau)
90% T90 or t0.9 none
99.3% T99 or t0.99 5 times the Sensor Time Constant (τau)

EXAMPLE: For a temperature sensor taken out of an ice bath at 0 °C into a room at 10 °C, it will take exactly: -T50 to reach 5°C -T63.2 (Sensor Time Constant) to reach 6.32 °C -T90 to reach 9°C -T99.3 to reach 9.93°C


Please note that T100 (or 100% of the final desired temperature) will never be reached because of the laws of physics.


All the reference data must be also related to the medium used for the test - you need to keep heat transfer and its circulation in mind.

Most commonly found mediums:

  • Water with circulation of 0.2 or 0.4 m/s
  • Air with circulation of 1 or 2m/s
  • And others, any medium needed can be used for the test

Water will have a much faster response times and the faster the circulation, the faster the response time.

Overview of Simple Hardware devices

We are using 4 types of devices:

Device SimplePack Temp SimpleMeter SimpleIndustry (internal probe) SimpleIndustry (NTC on case) SimpleIndustry (NTC on cable)
Placement Inside enclosed case Inside case with air intakes Inside enclosed case On the case On the pipe
T63 (sensor only) 15s at 1m/s airflow 15s at 1m/s airflow 15s at 1m/s airflow 4s 15s in water
T50 (whole device) 2min (water), 4min (air) 1min (air) 8min (air) 2s 12s in water
T63 (whole device) 3min (water), 5min (air) 1.25min (air) 10min (air) 4s 15s in water
T90 (whole device) 12min (water), 20min (air) 5min (air) 40min (air) 20s 1min in water