Ultrasonic Flowmeters – OPTISONIC 3400 for District heating and Cooling

Robust, ultrasonic flowmeter for District heating applications

OPTISONIC 3400 District Heating
  • Dedicated for thermal energy measurement
  • MID 2014/32/EU Annex VI (MI-004) approved
  • Accurate bi-directional flow measurement

The OPTISONIC 3400 flowmeter is an unique, 3-beam, inline, ultrasonic flowmeter, designed especially for measuring homogeneous conductive and non-conductive liquids, with high accuracy and reproducibility, over a long period of time. KROHNE is a main supplier for ultrasonic in-line process flowmeters for liquids with the largest global installed base / proven track record in terms of robustness and measurement accuracy. Building on vast knowledge and expertise, KROHNE now introduces the type approved OPTISONIC 3400 for district heating applications. 

The OPTISONIC 3400 features advanced meter diagnostics

This provides extensive self-checking of internal circuits and information regarding the health of the flow sensor, but just as importantly, vital information about the process and process conditions. 

The OPTISONIC 3400 features velocity of sound

Another unique feature of the OPTISONIC 3400 is the free of charge measurement of velocity of sound per acoustic path. For instance, this can supply information about pollution in the liquid, or changes in the process conditions. 


  • High performance signal converter for energy measurement applications
  • Completely welded construction, wear and maintenance free
  • Full bore, unobstructed sensor tube, without pressure loss and without moving parts
  • Accurate bi-directional flow measurement, with three beams to measure continuously
  • No influences of scaling
  • Compact dimensions and easy installation and commissioning

Legal Metrology / MI-004 Approval

For thermal energy measurements OPTISONIC 3400 for District heating is Class 1, 2 and 3 approved according to the latest Measurement Instrument Directive 2014/32/EU Annex VI MI-004, reflecting our extensive experience in providing Custody Transfer measurement solutions in a range of industries and applications.

Heat metering systems consist of 3 main parts: temperature sensors, flowmeter, heat calculator. Heat demand is regulated by flow rather than by temperature. Therefore at low energy demand, low minimum flow measurement is a critical factor. Ultrasonic flow measurement starts already at zero flow, and is MI-004 approved starting from 0,1 m/s.