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Thermowell selection guide

When choosing the correct thermowell for a temperature sensor installation, there are two possible approaches:

  1. The first and ideal approach is to choose the thermowell before the temperature sensor. This is because the thermowell’s process connection and installation length will be what is installed into your machine or application.

  2. The second approach is applicable if you have already selected a temperature sensor, and in this case, you will need to ensure that the thermowell and temperature device are compatible.

Below, we will explain the terms used on the datasheets of ifm thermowells and provide guidance on how to determine whether a thermowell and temperature device are compatible.

On the Industrial thermowells page and Sanitary thermowells page, you can find a variety of thermowells that ifm offers.

 

Explaining the dimensions and datasheet of a thermowell

Scale drawing and Technical details using E37210 as an example.

Approach 1

Using the above explanation of the thermowell datasheet, follow these steps:

  1. Determine the length needed for your installation and compare to the datasheet specification [1] Installation length EL [mm] under Mechanical data.
  2. Determine your desired process connection for threading or mounting into your application and compare to the datasheet specification [5] Process connection under Mechanical data.

These are the only two specifications that are important when choosing a thermowell. Once the proper thermowell is chosen based on the desired process connection and installation length, determine which temperature sensor is compatible with your chosen thermowell by using Approach 2.

 

Determining sensor and thermowell compatibility

Scale drawing and Technical details using TA2333 as an example.

Approach 2

Using the above explanation of the ifm temperature datasheet, the following four specifications are important when determining compatibility between a thermowell and temperature device:

  1. [1] EL on the sensor data sheet is the temperature sensor's probe length and should match [3] Design for temperature sensors EL on the thermowell data sheet to ensure the temperature probe bottoms out in the thermowell. This guarantees a fast and repeatble temperature measurement.
  2. [2] Process connection on the sensor data sheet should match [4] Sensor connection on the thermowell data sheet. These need to match in order to adapt the temperature sensor or RTD to the internal thread of the thermowell.

Note: Compression fittings are offered as accessories for RTDs and temperature sensors with 6, 8 or 10 mm diameter probes. When a compression fitting is used, the probe's [1] EL specification needs to be at least 25 mm longer than [3] Design for temperature sensors EL in order to bottom out in the thermowell.

If an ifm temperature device is not being used:
The temperature devices's installation length or probe length will need to be determined and can subsitute [1] EL in step 1. The temperature device's [2] Process connection will also need to be confirmed for step 2.