Simplifying flowmeter verification testing

Maintenance, Test & Measurement, Calibration

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April 2002 Maintenance, Test & Measurement, Calibration

Continuous accuracy measurement - or the ability to accurately carry out verification tests without discontinuation of flow - is becoming the battleground where boundaries are drawn and redrawn by instrumentation manufacturers fighting for supremacy.

Having established a strong base in this field with its patenting of unique insulation and magnetism test principles, Danfoss claims to currently lead the market with its electromagnetic Magflo Verificator. "A fully automatic verification test involves three important components, namely a signal converter, flowmeter insulator and magnetism sensor," Danfoss business unit manager - Motion Controls and Flow, Mick Baugh, explains. "We have developed the Magflo Verificator to the point where it now carries out an entire test, covering all three principles, within 15 minutes of being connected, without interrupting flow or disconnecting any cabling or existing devices such as analog or digital outputs etc."

To ensure an accurate measurement, the Verificator must test the whole signal chain in the flowmeter, including sensors, cabling and converters. Starting with power to drive the magnetic field, the Magflo tests all these elements, including continuously stable magnetic behaviour, converting flow velocity to a flow signal, ensuring the flow signal is received correctly without disturbance, ensuring correct connection for accurate flow signal, correct signal processing and calculation and correct flow signal on output.

By comparing the current sensor magnetism with a 'fingerprint' which was determined during initial calibration and stored in Danfoss' unique, patented SENSOR-PROM, the Verificator ensures that magnetism levels are identical to when the device was first calibrated. Flowmeter insulation testing is a 'crosstalk' test of the entire flowmeter, which ensures that the flow signal generated in the sensor is not affected by any external influences. Converter verification checks the whole electronic system, from signal input to flow output. Using the excitation power output generated to drive the sensor's magnetic field, the Verificator simulates flow signals to the converter input. By measuring the converter outputs, it calculates accuracy against defined values.

"This is just another improvement to the Danfoss Continuous Accuracy programme (DCA)," enthuses Baugh. "As we entrench ourselves more and more in the leading position with regard to continuous flow measurement, I have no doubt that the overall benefits of having a flow process not only operates uninterruptedly, but also continuously accurate, will lead to significant growth for Danfoss in this market."

Mick Baugh, Danfoss

011 803 8390

danfoss@danfoss.co.za

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Maintenance, Test & Measurement, Calibration

Simplifying flowmeter verification testing

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