Emerson ultrasonic flow meter is accurate to 0.5% even in variable weather conditions


Emerson's Mobrey MCU900FH ultrasonic open channel flow meter.

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Grace Capwell
Emerson Automation Solutions
+1 (512) 834-7214

Independent trials by SW Water show MCU900FH is almost immune to effects of insolation

AUSTIN, TEXAS (May 12, 2008) -- Trials carried out by SW Water using a fixed flow-rig over a nine-month period have shown Emerson’s Mobrey ultrasonic open channel flow meter, the MCU900FH provides reliable high accuracy even in variable temperature conditions.  Results from the trials show the MCU900FH generally achieves accuracy to within 0.5% right across the range of UK weather conditions from winter to summer.

SW Water carried out the trials in an effort to identify a robust, cost-effective, ultrasonic level meter, with performance reliable enough for use in flow measurement to MCERTS Self Monitoring of Effluent Flow standards on its 280+ waste water treatment sites.  The experiment ran from January to September 2007.

Robin Lennox, ICA specialist for SW Water explained,  “Our regular verification checks of the ultrasonic level meters used in our open channel flow installations were showing markedly different results for different weather conditions.  Discrepancies of as much as 9% were occurring between measurements taken on a cold, cloudy day, and those taken in warm sunshine.”

“In order to meet the MCERTS regulations on effluent discharge, we are looking for a level meter reading with a consistent uncertainty of no more than plus or minus 0.5%,” says Lennox.  “This gives an uncertainty of around 3 or 4% on the final flow reading, which when taken with other uncertainties (for example from the flow structure) enables us to meet the MCERTS requirement.”

Designed for use in open channel flow applications, MCU900FH features a pre-wired remote temperature sensor that accurately measures the ultrasonic path temperature and compensates for inaccuracies caused by solar gain – a common problem with conventional transmitters. 

“Our test rig was designed to eliminate all variables that might have affected the readings, other than the weather," said Lennox.  "We ran the experiment continuously for nine months so as to include data from cold, wintry conditions, hot summer days and everything in between.   Our trial was successful, and after analysis of the results we selected the MCU900FH for our MCERTS ultrasonic applications.”

 Emerson water industry expert Peter Ward said, “Open channel flow systems are routinely exposed to variable weather conditions which can affect their accuracy.  Organizations which carry out annual calibrations should verify their measurements regularly through the year and in varying weather conditions in order to ensure they are complying with the MCERTS regulations.”

The Mobrey MSP900FH is 24V DC loop powered, supplied in a waterproof housing sealed to IP68.  It has both analog 4-20mA communications and digital HART options built-in, and can be used stand-alone, or as part of a site-wide measurement, control and data acquisition system.

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Emerson (NYSE: EMR), headquartered in St. Louis, Missouri (USA), is a global technology and engineering company providing innovative solutions for customers in industrial, commercial, and residential markets. Our Emerson Automation Solutions business helps process, hybrid, and discrete manufacturers maximize production, protect personnel and the environment while optimizing their energy and operating costs. Our Emerson Commercial and Residential Solutions business helps ensure human comfort and health, protect food quality and safety, advance energy efficiency, and create sustainable infrastructure. For more information visit Emerson.com.

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