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Temperature Measurement · Glossary

What is Insertion Length?

Symbol: Uimmersion of the well or sensorTemperature Measurement

Insertion length is the length of a thermowell or sensor that projects into the process from the mounting point.

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Insertion Length Explained

Too short an insertion lets heat conduct along the well to the outside, so the sensor reads closer to ambient. Too long an insertion raises vibration risk.

A common rule of thumb is an immersion of at least about 10 times the well diameter in liquids, more in gases. Check the thermowell calculation for the final length.

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Calculators for Insertion Length

CalculatorSensor Response Time CalculatorFree online calculator with formula and worked example.CalculatorPipe Heat Loss CalculatorFree online calculator with formula and worked example.

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Frequently Asked Questions

What is Insertion Length?

Insertion length is the length of a thermowell or sensor that projects into the process from the mounting point.

What is U length?

The insertion length of a thermowell below the process connection, the dimension usually called U in data sheets.

Where should the tip be in a pipe?

Often in the middle third of the pipe; small lines may need an elbow installation.

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Thermocouple and RTD installation precautions

A practical guide on instrumentationblog.in with more detail on insertion length and how it is applied on real plants.

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All temperature measurement terms · Full glossary A to Z

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