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Cole Parmer UK’s range of ultrasonic flow meters and doppler flowmeters offers process contamination free measurement of liquids and gas flow. A typical ultrasonic flow meter will consist of a transducer that is mounted on to the exterior of the pipe and an indicator or totalizer to display the output. This can easily be installed without disturbing existing pipe work. Most ultrasonic flow meters will work with pipe sizes between ˝” and 200” diameter. There are two main types of ultrasonic flow meters, doppler flow meters and time transit ultrasonic flow meters.
A doppler flow meter requires particulates or bubbles in the media. The minimum diameter size of the particulate is typically 30 microns and requires a minimum concentration levels of 25 ppm. Since some meters may require slightly larger concentrations of particulate, it is a good idea to check the specifications table. Doppler flow meters are mainly used for liquid applications (roughly 88%) while the rest are used for gas (11%) and steam (1%) applications.
A time transit ultrasonic flow meter requires a clean liquid without particulates or bubbles and can be used for both liquid and gas applications. It has better accuracy than that of a doppler flow meter and will typically offer accuracies of ±2% full scale.
To find the right flow meter for your application use Cole-Parmer’s on-line flow meter quick search. Alternatively contact our Application Specialists for free technical support and let us bring over 50 years of flow control experience to help solve your application needs.
Key Points for ultrasonic flow meters
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| The doppler flow meter and the time transit ultrasonic flow meter measure the frequency shift of an ultrasonic signal sent through the media. In the case of a doppler flow meter it utilises particles or bubbles in a fluid as a reflective mechanism to gauge the velocity of the media. For a time transit ultrasonic flow meter it relies on a frequency difference in forward and reverse signals sent through a clean liquid to gauge the velocity of the media. |
- A ultrasonic flow meter has an accuracy of typically ±2% full scale
- A ultrasonic flow meter normally has a turn down ratio in the region of 20:1
- Ultrasonic flow meters are non intrusive
- Ultrasonic flow meters can be used with a wide variety of pipe materials, but some will not allow the signal to pass through. Although pipe material recommendations will vary depending on the sensor design, you should not expect to have any problems with carbon steel, stainless steel, PVC, and copper. However, pipes made of concrete, fibreglass, iron, and plastic pipes with liners can pose transmission problems.
Advantages for ultrasonic flow meters
- Process contamination free measurement of flow
- No leak potential
- Allows for easy installation without disturbing existing pipe work
- Suitable for aggressive chemicals as no contact with the media
- Doppler flow meters are suitable for slurries
Disadvantages for ultrasonic flow meters
- Requires sufficient knowledge of the flow and media to give some confidence in readings
- Higher initial setup costs than other flow technologies
- Pipe material must be compatible with ultrasonic sensor
Typical Application for ultrasonic flow meters
- Influent and effluent water flow (doppler flow meters only)
- Clarifier monitoring
- Digester feed control (doppler flow meters only)
- Waste water (doppler flow meters only)
- Cooling water
- Makeup water
- Pure and ultra-pure fluids in semiconductor, pharmaceutical, and the food & beverage industries (time transit ultrasonic flow meters only)
- Acids and liquefied gases in the chemical industry
- Light to medium crude oils in the petroleum refining industry (time transit meters only)
- Water distribution systems used in agriculture and irrigation
- Cryogenic liquids (time transit ultrasonic flow meters only)
- Gas-stack flow measurement in power plant scrubbers
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