Buyer guide: KROHNE OPTIMASS 7400 and Proline Promass I 300

A warm welcome to our readers in yet another product review. Today we have two Coriolis flow meters here to show off their fancy tech. Curious? Then keep reading!


 KROHNE has a massive front in the field of automation. Today we’ll go over the OPTIMASS 7400. Let’s see if this device meets your demands!


The OPTIMASS 7400 sports an LCD display with 256 by 128 pixels and a white backlight to enhance its data. It also has four push buttons for the local setup. The touchscreen makes things nice and current, and the infrared interface lets you set up the device without cracking open the housing.

Courtesy of KROHNE

The device supports HART, FOUNDATION Fieldbus (FF), PROFIBUS PA/DP, and Modbus RTU. And for output, you get analog, pulse, frequency, and status. If you want Ethernet, then KROHNE has that on a different device in the OPTIMASS series.

The 7400 comes in sizes from a quarter inch to three inches with a list of wetted materials like titanium, stainless steel, and tantalum. So one of them should work in your application.


The OPTIMASS 7400 can measure mass flow, temperature, and density. It can also support volume flow, referred density, concentration, and velocity.

In accuracy, it gets around 0.1 percent of flow rate plus zero stability in liquid, and gas has 0.35 percent. Then your standard density hits two kilograms per cubic meter. If you want better numbers, then an on-site calibration brings it up to 0.5. And the standard temperature accuracy is one degree Celsius.

Courtesy of KROHNE

The temperature range depends on your wetted material. Titanium gives you -40 to 150 degrees Celsius and stainless steel 0 to 100, with an extended version up to 130. Hastelloy and tantalum also get 0 to 100 degrees Celsius. Then we have pressure. Titanium supports -1 to 100 bar, and stainless steel, Hastelloy, and tantalum -1 to 50 bar.


The 7400 has a few special features. The Entrained Gas Management (EGM) application enables the meter to work with gas and liquid mixtures, slurries with gases, and a lot more.

You can also get advanced diagnostics with NAMUR NE 107 – nothing new but still nice. Best of all, this device has redundant data storage!

 Proline Promass I 300

Endress+Hauser also puts it down in the instrumentation world. Do we have something new in the I 300 of the Promass series? Scroll down to get some answers for that!


The Promass I 300 comes with a four-line graphic display and a white backlight that turns red when it detects bad juju. And you can set up locally with the push buttons or get all fancy with the WLAN option!

The Promass I 300 supports HART over analog, PROFIBUS PA, FF, and Modbus RS485. Though it lacks wirelessHART, EtherNet IP, PROFINET, or PROFIBUS DP, E+H may add these later. And lest we forget, you have pulse, status, and frequency too.

You can get a measuring tube somewhere between three-eighths of an inch and three inches. You can also get a full-body option to reduce pressure loss.


Like any Coriolis meter, the Promass I 300 can measure mass flow, density, and temperature. It also does viscosity! That’s kinda different! And from this data, you can calculate reference density, volume flow, and concentration.

The I 300 yields an accuracy of 0.1 percent for mass and volume flow, 0.105 percent in gas, and 0.0005 grams per centimeter in density. And the star of the show, the viscosity, shines at 0.5 percent with a repeatability of 0.05 percent for Newtonian liquids.

Promass I 300
Courtesy of Endress+Hauser – Proline Promass I 300

Finally, it can handle -50 to 150 degrees Celsius and Class 600 pressure. You get grade 9 titanium for the measuring tube with connections in grade 2.


 Endress+Hauser’s Torsion Mode Balanced (TMB) system measures that viscosity to educate you on your process quality. Plus, the I 300 offers solid accuracy and repeatability.

And the WLAN lets you connect your tablet, smartphone, or laptop to the device. You can set this meter up through the WLAN or EtherNet IP using the built-in web server too!

Finally, E+H has Heartbeat Technology to monitor your device’s condition. This feature can prevent problems and unscheduled downtime and extend the time between calibrations. Pretty sweet, if you ask me.

Table of comparison

Category Proline Promass I 300 KROHNE OPTIMASS 7400 Verdict
1 Unboxing four-line graphic screen with white backlight that turns red for alerts; three push buttons for local setup; simple setup and decent user experience clear LCD display; choice of integrated or remote without switching models; four optical keys for local setup; infrared option; good user experience tie
2 Measurement and sensor mass flow, density, temperature, and viscosity; grade 9 titanium sensor with grade 2 connections; -50 to 150 degrees Celsius with Class 600 pressure; ⅜ to 3 inches with full-body option to reduce pressure loss mass flow, density, and temperature;  titanium, stainless steel, hastelloy, or tantalum for wetted parts; -40 to 130 degrees Celsius and pressure range varying between materials I 300
3 Field protocols and outputs HART, FF, Modbus RS485, and PROFIBUS PA; analog, pulse, frequency, and status HART, Modbus RTU, PROFIBUS PA, and PROFIBUS DP; analog, pulse, frequency, and status 7400
4 Performance liquid accuracy 0.1 percent; density 0.0005 grams per cubic centimeter; gas 0.5 percent; viscosity 5 percent with 0.5 percent repeatability liquid accuracy 0.1 percent; density 2 kilograms per cubic meter; gas 0.0355 percent I 300
5 Special features WLAN; internal web server; Heartbeat Technology; Torsion Mode Balanced (TMB) system Entrained Gas Management (EGM); NAMUR NE107 diagnostics; redundant data storage tie
6 General information and documentation weak site; no mobile platform; poor user experience same, same, same tie


The viscosity measurement on the I 300 makes for a nifty feature, but beyond that, it resembles the 7400. If you need to measure viscosity, then you have one choice, the I 300. If you need different wetted materials and a few nice features, then check out the 7400.

Buy the Proline Promass I 300 in our online shop


Find and buy the right Coriolis flow meter for your application

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