How does the Transit-Time Ultrasound Method work?

em-tec offers many different flow measurement systems which are based on the transit-time ultrasound principle:

Transducers consist of four piezoceramics housed in a fixed location within the transducer body. The piezoceramics are arranged in an “X” pattern which acoustically illuminates the whole cross section of the flow channel by four sound paths. A high frequency voltage impulse is used to excite the piezoceramics and transmit ultrasound waves from one ceramic to the opposing one, with each one acting alternately as transmitter and receiver. The length of time it takes the signal to travel from one crystal to another (transit time) is measured by the electronics of the flow transmitter. The difference between the upstream transit times (against the flow) and downstream transit times (with the flow) is proportional to the volumetric flow rate.

Non-invasive Flow Measurement in Blood Vessels

Vascular Probes for non-invasive flow measurement in blood vessels work on the same transit time principle but only have two crystals. Ultrasonic impulses are sent from one piezo crystal to another via the reflector, with the crystals acting alternately as transmitters and receivers.

Technology / Applications

Examples for use in bio-processes or in any other processes with strict hygiene requirements:

  • Bioreactors
  • Fermenter
  • Sterile filling processes
  • Pump feedback control loops
  • Tagnential Flow Filtration
  • Chromatography
Examples of applications for flow measurement on blood vessels:

  • Cardiovascular Surgery: Measurement of bypass grafts, Detection of stenosis
  • Vascular Surgery: Detection of arteriovenous fistulas during in-situ bypass surgeries, Intraoperative graft patency control of distal-femorotibial bypass grafts (CABG), Functional Assessment of Dialysis Shunts
  • Transplant Surgery: Measurement of perfusion during liver and kidney transplant

Extracorporeal flow measurements:

  • Extracorporeal Membrane Oxygenation (ECMO)

The use of clinical procedures and techniques is the sole responsibility of the physician.


Partners in Science

We place great importance on our partnerships with world-renowned research institutes and universities. Our network is the result of many years of cooperation in which we have created symbioses with scientific collaborators.

We also support valuable research in the field of medical science, an integral part of the launch of new medical devices. Take advantage of our expertise when developing your next new product!

Some of our partners:

  • Fraunhofer Institut, St. Ingbert
  • Munich University of Technology
  • University Hospital “Rechts der Isar”, Munich
  • Grosshadern Hospital, Munich
  • Heart Centre, Munich
  • University of Applied Sciences, Ulm
  • Texas Heart Institute, USA
  • German Aerospace Centre, Oberpfaffenhofen


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