OPTIMASS 7400 vs Proline PROMASS I 300

I had a great time with my last flow measurement project in Brazil. The customer, a big Brazilian food company, had some natural gas to measure. This application only needed the totalization of the flow measurement, so it sounds easy, yeah? But it was outside the process area, with no structure for the meter’s power or communication.

We installed a Coriolis flow meter with a high level of gas accuracy, a solar panel, and batteries. To connect the device with the control system, we used WirelessHART protocol and a data logger to register all information coming up from the device.

It worked perfectly. You could see the system running, the device measuring, and the wireless sending numbers by the minute from the flow meter to the data logger. And it still works to this day, thank you very much! #wirelessislife

Now, let’s check out the companies who’ll provide the show today! These crews already know how the comparison works. On the left, Endress+Hauser shows up again at Visaya, bringing the new Proline PROMASS I 300 to the ring. On the right, KROHNE has the OPTIMASS 7400 and its outstanding features. Let’s find out how these devices can support your new flow application!

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


We opened the Proline PROMASS I 300 from Endress+Hauser first, and it made a good first impression. I like the housing design and the display. It has a graphic screen with four lines and a white backlight that switches to red when you have a problem with the device. It also has three buttons to set up the device and check information locally. The 300 is an integrated version, where you have the measuring tube and the transmitter together. For a remote version, you need to switch to the electronic 500. Both offer a good user experience during setup; you can navigate the menu tree quite easily.

Promass Proline I 300
Courtesy of Endress+Hauser and KROHNE

The OPTIMASS 7400 also makes a good first impression. I mentioned in the review that it feels robust and has a beautiful display as well. The LCD clearly shows the process variables and bar graphs for data at a glance. Unlike the Proline PROMASS I 300, you can choose an integrated or remote version without switching models. It too offers local configuration, with an optional feature to set up the device using infrared communication. Frankly, this feature feels outdated and slow to me. Anyway, the four optical keys provide a good user experience, so you’ll get through the setup quickly here too.

Measurements and sensors

Both devices offer mass flow, density, and temperature. But the PROMASS I 300 sneaks in a secret weapon the OPTIMASS doesn’t have, in-line viscosity measurement! Point to the E+H crew!

The Proline PROMASS I 300 has its sensor in grade 9 titanium and connection in grade 2 titanium. It can support a process temperature range from -50 to 150 degrees Celsius, with a maximum pressure of Class 600. The size options start at three-eighths of an inch and go up to three inches, with an optional “full-body” version that reduces pressure loss.

Coriolis flow meter
Courtesy of KROHNE

The OPTIMASS offers a broader range of wetted material than the PROMASS. You can choose titanium, stainless steel, Hastelloy, or tantalum! Not bad, huh? Temperature ranges differ according to the material, but the minimum is – 40 to 130 degrees Celsius. You can see the details here. The pressure will also vary; the titanium goes from -1 to 100 bar, and the others from -1 to 50 bar.

Field protocol and output

The 300 has some promise – but hasn’t delivered yet. If you go to the configurator, you can see the possibilities marked as not available! You can only look at the WirelessHART, EtherNet/IP, PROFINET and PROFIBUS DP. Disappointing. However, it does have HART, PROFIBUS PA, FOUNDATION Fieldbus (FF), and Modbus RS485. It also has universal outputs, where you can choose analog, pulse, frequency, and status.

The OPTIMASS 7400 has HART, FF, PROFIBUS PA, PROFIBUS DP, and Modbus RTU! Unfortunately, KROHNE has no promise to launch disruptive tech like Endress+Hauser. This goes back to company strategy, so maybe KROHNE’s customers don’t need or want these protocols. Who knows?


Now for the numbers, everybody wants! Of course, if you want to see the real performance in your application, then you need to – you got it! – SCALE OUT. But to get you started, both devices offer similar standard performance on paper.

Proline Promass I 300
Courtesy of Endress+Hauser and KROHNE

On the Proline PROMASS I 300 side, you get a liquid flow accuracy of +-0.1 percent for mass and volume, density at +-0.0005 grams per cubic centimeter, and +-0.5 percent in gas. It took me 45 grueling minutes to find the viscosity accuracy, +-5 percent with an excellent repeatability of +-0.5 percent.

The OPTIMASS 7400 appears with a liquid accuracy of +-0.1 percent in mass and volume, +-0.035 percent in gas, and +-2 kilograms per cubic meter in density. And because the 7400 doesn’t do viscosity, that’s all from that side.

Fancy features

Finally, we get fancy again! We have premium options here, so yes, they have fun features! First, the transmitter from Endress+Hauser has the option of wireless communication (WLAN) to let you set up the device using your phone, tablet or laptop. It also has an internal web server, so you don’t need any software to get set.

Heartbeat Technology
Courtesy of Endress+Hauser and KROHNE

Another feature connected to E+H’s Industrial Internet of Things (IIoT) strategy is the Heartbeat Technology, providing detailed information about the health of the device. You can read more about that here. But the rock star of this show is the patented Torsion Mode Balanced (TMB) system™! E+H developed this tech to measure viscosity using a Coriolis flow meter, and it’s sweet!

The OPTIMASS 7400 has a couple tricks up its sleeve, don’t worry. If you have entrained gas, you want this device! The crew from KROHNE developed Entrained Gas Management or EGM™, another patented technology to improve your process. It’s not unique like the TMB system, but it’s still a nice feature. You also get advanced diagnostics based on  NAMUR NE107 and redundant data storage, giving you more security.

Information and  documentation

Hate to say it, but the Endress+Hauser site still needs improvement. For this product review and comparison, I spent a ridiculous amount of time trying to find basic information that should have appeared on the device’s first page. No sign of a phone or tablet version yet, either. Sad.

Coriolis flow meter
Courtesy of Endress+Hauser and KROHNE

KROHNE’s site falls in the same mucky bucket. I found the button to scale out the meter only because I’m a lucky guy. Otherwise, I would never have guessed that this icon led to the configurator tool. Blah.


If you need a flow meter that measures viscosity, then get the Proline PROMASS I 300. If you don’t care about viscosity, then both devices offer similar performance. The OPTIMASS 7400 has a better range of wetted materials, but the 300 has the fanciest features. Scale them out to find out how well they would perform in your process, check their prices and your wallet, and decide if the fancy features do anything for you.

Table of comparison

Promass I 300 vs OPTIMASS 7400
Courtesy of Endress+Hauser and KROHNE
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