Comparison: Endress+Hauser iTHERM TrustSens TM371 vs WIKA TR21

Do you need a new thermometer for your hygienic process? Then you need to take a few minutes and learn more about the devices here.

Today, we have the newest roll-out from Endress+Hauser, the iTHERM TrustSens TM371, and the TR21, from WIKA – both compact, flexible, and aseptic thermometers! Let’s check ’em out!

Disclaimer: This product review examines only features, not performance. If you’ve used this device, feel free to share your experience in the comments.

Product Review iTHERM TrustSens TM371

First impression

For sanitary or aseptic applications, the design has an impact on one of the most important points, contamination, as well as others. Although both thermometers look simple and compact, that doesn’t mean the developers skimped on finding the best design.

The TrustSens TM371 has such an elegant, simple look that it may fool you. E+H has a neat trick tucked into that housing! More on that later. And of course, the compactness makes it fit anywhere in your process without issues.

The TR21 is also a compact, flexible and straightforward thermometer. Like its competitor, its simple, compact design holds many features and functions, including the ability to fit in small spaces and many processes.


On the downside, the TM371 doesn’t have a local display, but then most similar thermometers don’t either. On the upside, the company offers the RIA15 as a go-to solution. This compact screen has three push buttons and a simple interface for local setup, making for a good user experience. The loop-powered display operates with either HART or analog communication. However, you can pick any other similar display on the market, if you want to diversify.

No native display on the TR21 either, and it only has analog. WIKA didn’t have a default recommendation or any simpler solution than a temperature controller. However, if you Google “analog display,” you’ll get a broad range of options from many brands. The lack of HART still limits you, though, in choice as well as data.

TrustSens TM371 vs WIKA TR21
Courtesy of Endress + Hauser & WIKA

Sensor and process connections

Both thermometers use resistance temperature detection (RTD) to measure temperature. The TM371 uses a PT100 and has a range of -40 to 160 degrees Celsius, with a maximum static pressure of 40 bar at 20 degrees Celsius.

It also has a bunch of process connections to make installation easy and keep your process clean – clamp, compression fittings, weld, and others.

WIKA’s device has a few small differences. First, you can order the thermometer with PT100 or PT1000. Second, its range goes from -30 to 250 degrees Celsius – higher than its rival but not as low. And third, its max pressure depends on the process connection and thermowell.

The TR21 also comes with an extensive list of process connections to make your life comfortable and help you avoid adapters. However, you have to pick a model: the TR21-A does the flange thing, the TR21-B works for orbital welding, and TR21-C has an integrated sterile connection. The datasheet shows the entire list of possible connections, so check it out before you decide.

You can find the insertion length on the datasheet too, or the website. The TR21 offers 25 to 200 millimeters, but Endress+Hauser has a typo somewhere. The website says max 900, but the configuration tool says 700. Still waiting for a reply:

Answer from Endress+Hauser: “The immersion length up to 900mm is on request while the 700mm is available as a standard.”

Performance, integration, and approvals

The TrustSens TM371 has a good response time highlighted on the website, with 2.5 seconds for a T50 and 9.5 seconds for a T90. The manual will fill you in with details and tables if you want to learn more.

Given the requirements for hygiene, the device needs certifications and approvals out the wazoo. The TrustSens TM371 has international approvals, regulations, protection classes, and so on. Check out this alphabet soup: EHEDG, FDA, 3-A, IP69K, and more.

You can integrate into your system with either analog or HART communication, pretty standard options for these industries. However, some application do use PROFIBUS. E+H could beef up this thermometer with more protocols and a sprinkle of Bluetooth dust. Why no Bluetooth? SmartBlue? Dunno.

The TR21 has also a good performance, based on IEC60751, with a T50 at less than 4.7 seconds and a T90 at less than 12.15 seconds. You can read more about it in the documentation. On the downside, it lacks integration options. You can integrate the sensor directly using the three- or four-wire version without a transmitter, or you can do it through analog. Sadly, if you choose the path of the transmitter, then you’re stuck using proprietary software for your setup.

You can read here about the pros and cons of the options to integrate sensors into your control system.

On the upside, it has plenty of approvals, certifications, and all that stuff: IECEx, UL, 3-A, EHEDG, IP67, and more.

Fancy features

In this topic, we have a vast difference between both thermometers. The TrustSens TM371 uses the Curie Temperature (Tc) procedure to calibrate itself. Yup, you read that right.

It has a ceramic body for the reference that changes at 118 degrees Celsius. During the sterilization in plant (SIP), you heat the process above 118 degrees Celsius. When the temperature falls back to 118, the ceramic body changes. Then the device compares the temp of the PT100 with a reference measuring point to find the sensor deviation.

It has a green LED to indicate the calibration procedure, and it saves the results automatically. Through a device management system, you can print the report if necessary. You can also choose the iTHERM QuickNeck as an easy way to install and remove your sensor from the process.

You can calibrate the TR21 without opening the process; it allows you to remove the device quickly. And that’s it! No bells or whistles on this one.

Information and documentation

Nothing new on the Endress+Hauser site. Still sucks on desktop, laptop, tablet, and smartphone. Once you finally find the documents you want, things become a little easier, but it takes more than that to win my favor.

WIKA stuck to a conservative design. If you know what you want, then you can find it easily. Otherwise, it also gets frustrating. The tech docs are clear and easy to download when you find them.

Neither site brings much to the table.

TrustSens TM371 vs WIKA TR21 Websites
Courtesy of Endress + Hauser & WIKA

Table of comparison

TrustSens TM371 vs WIKA TR21 table of comparison


Both devices will support most hygienic and aseptic applications. If you want a smart device, the iTHERM TrustSens TM371 has advanced features and HART protocol. If you have no interest, then try the TR21. Both offer similar performance, so scale out, check the local support, price them, and pick the best for your application.

Buy the iTHERM TrustSens TM371 in our online shop


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