The industry has some good developments in temperature measurement, especially external temp devices. Vendors have begun to offer this new technology to provide better accuracy than clamp-on sensors. These devices first came out on the wireless technology wave, but now even wired solutions have these sensors integrated.

Although this new tech still has a few challenges and limited applications, buyers have warmed to the idea. (Sorry, couldn’t resist.) After all, the installation of a new temperature point involves a lot of effort – scheduled downtime, extra materials, welding, labor, and so on. Surface devices install easily with very little labor or time.

Tell us your thoughts on this new tech in the comments!

Now, on to the review! SMAR, a Brazilian company with an international presence, has presented Visaya with a traditional model to examine. The TT301 may give us a twinge of nostalgia, but this device can help in new applications, so let’s check it out! Although SMART has newer models in its portfolio, the 300 line remains the most popular. Therefore, it makes sense to review it first.

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

Whatcha got there?

The SMAR TT301 has spent a long time on the road and supported a lot of applications around the world. Several transmitters in the SMAR portfolio echo its simple design, with only the sensors showing any changes.

The SMAR TT301 has a local LCD display, where you can see your process variables and diagnostics. However, its design and data layout feel outdated compared to other brands. Still, it gives you what you need to operate it locally. You can also set it up locally using its magnetic – screwdriver? Let’s call it a pen. It can provide the zero and span adjustments, but you need the magnetic pen to set those up.

Courtesy of SMAR

The size of the device is pretty standard, 0.93 kilograms with the display and 1.53 with the support structure. As for input, you have many possibilities with the SMAR TT301. This device mainly uses thermocouples and resistance temperature detectors (RTDs), but it can also read millivolts and resistance from sensors that use those. These options allow you to use the device for more than just temperature.

What can it do?

Temperature measurement, of course! You can use nearly any thermocouple or RTD in the SMAR TT301. Or you can get creative with it, such as in a weight application, where you use load cells with millivolt output. The transmitter from SMAR can read this data and send it to your local indicator or the control system.

Courtesy of SMAR

The model TT301 only offers analog with HART communication. However,  the TT302 handles FOUNDATION Fieldbus (FF) and the TT303 PROFIBUS PA (PB). Same device, just different numbers for different protocols. The power source for the HART device ranges from 12 to 45 volts of direct current, and the FF and PB devices need 9 to 32. And the device offers an accuracy of +-0.02 percent.

Why should I care?

True, we won’t find any innovative technology here. SMAR keeps the device simple and fancy-feature-free. But you can still find features on it that may help you with specific applications.

For instance, the TT301 has an optional integrated controller. This addition can help if you have a simple application or your company lacks other instrumentation. The device can measure and control the variables, giving you two abilities in one transmitter.

Courtesy of SMAR

And here’s a tidbit for you – some of SMAR’s developers pioneered advances in FF communication. This background allowed them to provide up to 20 function blocks for the TT302, so you can run advanced strategies with it. If you download the function block manual from SMAR, then you’ll get a complete list of blocks and good explanations about them.

Sadly, the English website lacks good interface options, lowering the user experience. The site makes it hard to find information, but oddly enough,  downloading documentation you need is fairly easy. Go figure.


The TT301 brings a long history of use in varied applications with it, and everyone knows that the TT301 is a robust device. If you want to consider a simple yet tried-and-true candidate, check this one out.

This video teaches you how to set up a TT301 locally using the magnetic pen:

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