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Issue Date: 12th May 2008
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Emerson’s Mobrey ultrasonic flow meter accuracy is verified for effluent discharge application by South West Water
• Independent trials verify reliable 0.5% accuracy
over variable weather conditions and insolation to satisfy MCERTS requirements
Emerson Process Management has announced verification of reliable accuracy
of its Mobrey MSP900FH ultrasonic open channel flow meter for effluent discharge
application in trials carried out by South West Water. The trials were carried
out over nine months to confirm the meter’s 0.5% accuracy over variable
weather conditions and insolation effects across the range of UK weather
conditions from winter to summer.
“Our test rig was designed to eliminate all variables that might have
affected the readings, other than the weather,” explained Robin Lennox,
ICA specialist for SW Water. “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 MSP900FH for our MCERTS ultrasonic applications.”
SW Water carried out the trials in an effort to identify a robust, cost-effective,
ultrasonic level meterwith performance reliable enough for use in flow measurement
to MCERTS standards on its 280+ waste water treatment sites. The experiment
ran from January to September 2007.
“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,” continued Lennox. ”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, MSP900FH 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.
Emerson water industry expert Peter Ward says: “Open channel flow
systems are routinely exposed to variable weather conditions which can affect
their accuracy. Organisations 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 analogue 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.
Ends
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