Rosemount 648 temperature transmitter

Hey hey! How’s it going? Got another product review for you! Okay, maybe you’re going, “Emerson again? Come on!” Listen, this crew has more going on in temperature solutions than any other vendor on the market, plus they have cool products and long-term vision. Respect, yo.

Now Emerson and a few other companies want to push the concept of surface sensors. While it’s not new, it has a reputation regarding accuracy, and it’s not a good one. However, Emerson and the rest say they’ve solved this issue.

To make a long story short, let’s welcome the Rosemount 648 temperature transmitter, with its Rosemount X-well Technology sensor, from Emerson Automation Solutions! Let’s review its features and see if it offers innovative technology or not.

You know our routine – grab a beer, have a read, and draw your  conclusions!

Full disclosure: 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 Rosemount 648 temperature transmitter has wireless communication already built in. Frankly, it’s pretty much the same as all the other Rosemount transmitters. You can connect different sensors to the 648, like thermocouples, RTDs, ohms, and millivolts. If you’ve ever used a Rosemount transmitter, you probably already knew that. For those of you who haven’t, the flexible single input in the 648 gives you good options.

Rosemount 648 temperature transmitter
Courtesy of Emerson Automation Solutions

Wireless allows you to use the transmitter easily in a monitoring process. Of course, you need to have a wireless structure in place to do so. If you don’t have that, then you’ll need to buy a gateway to connect the transmitter to your control system.

The 648 makes integration easy, and you have different protocols to guarantee that it goes seamlessly into your control system. Because temperature is a slow process variable, the update time will more than adequately cover your process.

What can it do?

Let me guess. Temperature measurement? Look, I’m right! As I said before, you have various sensors that fit the transmitter for practically any application you have. You just need to scale out and check the best option for your application.

Rosemount 648 temperature transmitter
Courtesy of Emerson Automation Solutions

The transmitter also provides a good battery life, ideally up to 10 years. Of course, for your process, you’ll need to go to Emerson’s power module life calculator. This online tool will help you estimate how long the battery will last in your plant conditions.

For example, if you want the sensor to have a 1-second update time in an ambient temperature of 30 degrees Celsius, the battery will last less than a year. However, if you choose a 16-second update time in the same conditions, you can squeeze out nearly 7 years of juice. Set your time wisely!

Why should I care?

Because cool things happen when you combine the Rosemount 648 temperature transmitter with the 0085 pipe clamp sensor, also known as X-well! Emerson wants to make this solution a standard on temperature applications. The 648 combines the surface temperature, ambient temperature, and pipe information to calculate the temperature of the process, giving you no reason to install a thermowell. Good news, huh?

Rosemount 648 temperature transmitter
Courtesy of Emerson Automation Solutions

Installing an X-well sensor is simple and saves a lot of time and money compared with standard installations. You can also use the transmitter in applications other than monitoring. One caveat: You should avoid fast control loops, safety monitoring, and fiscal metering. This device doesn’t work as well in those applications.

So why use an external sensor anyway? Because it doesn’t need a structure for a thermowell. Also, having it outside means it won’t risk damage, as it would in a thermowell.

The 648 should give you an accuracy of around 0.225 degrees Celsius, although you’d best give the salesperson your process info to confirm that. Furthermore, the 648 has an extended-antenna option. That can give you a better wireless signal, so you can skip buying a repeater to collect data from way out in the field.

This video has more details about the 648 with the X-well sensor:

If you want to check out other options, have a look at these links:

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