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SU ultrasonic flow meters

Technology overview

Ultrasonic sensors consist of transducers that transmit and receive sound pulses and reflectors that direct the pulses from one transducer to the other. A pulse is sent through the medium and the sensor measures the time of flight from one transducer to the other. Then a pulse is sent in the opposite direction. The meter measures the difference in time and calculates the flow rate.

The speed of sound varies in air, oil and water. The sound signal is filtered via a medium selection on the meter so that only the expected time of flight is evaluated. If medium selection is not correct, the meter will display an error. For example, if the medium selection is water but there are air bubbles or turbulence in the pipe, the time of flight measurement will not match that for water and an error will occur.

Applications

Hydraulic power units

HPU case-drain flow rate is an indication of pump seal wear. It is often monitored with visual indicators only. What if you could get feedback to your PLC?

The SU flow meter can reliably detect case-drain flow rates and provide an alarm output when flow rates reach a critical level.

Flow monitoring of deionized water

Flow of nonconductive liquids like deionized water cannot be measured with traditional magmeter technology. What if you could monitor total flow volume of DI water?

The SU flow meter uses time of flight measuring technology, so it can be used on DI water and other nonconductive media. It has a totalizing feature and a temperature output as well.

FAQs

Q. Why does my SU display "SEnS"?

A. The speed of sound is different as it travels through different media. With a given medium setting, the SU expects to see time of flight measurements in a certain range. If the measurements are outside of this range, the sensor displays this error. Check the “MEdI” setting on the sensor and check for air bubbles in the medium.

Q. Can the SU monitor diesel fuel?

A. The SU has two different oil settings in the “MEdI” parameter. “OIL.1” is for oils with viscosity of 30…68 cSt at 40 °C. “OIL.2” is for oils with viscosity of 7…40 cSt at 40 °C. Typically, “OIL.2” can be used for diesel fuel; however, the application should be tested as some additives can affect the speed of sound through the media. If it cannot be detected properly, you will see “SEnS” on the display.