Moving Liquid Through Vibration

Matchbox-sized sensor can do in-line measurements of transmission fluids, process liquids, or human blood

By Design News Staff -- Design News, December 5, 2005

For decades, engineers have measured viscosity with mechanical means.

Now, a new technique uses electronics to measure the viscosity of a fluid, thus enabling fast, real-time measurements of liquids ranging from helicopter transmission fluid to human blood.

The new technique accomplishes that through the use of a quartz crystal sensor incorporating input and output transducers, an oscillator circuit, and a microprocessor. During operation, electrical current is applied to the input transducer on the bottom side of the crystal. Using the oscillator circuit, the system then generates an acoustic wave, which travels through the thickness of the sensor and into the fluid to be measured. With the fluid (which sits on the top side of the sensor) vibrating at frequencies reaching 160 MHz, the molecules in the liquid move, causing energy to dissipate. By measuring the resulting power at the output transducer, and using the microprocessor to compare it to the original power at input transducer, viscosity can be immediately calculated. The trick, say engineers, is to understand that the fluid's viscosity is directly proportional to the power change.

The result is a matchbox-sized sensor that can be used for in-line, real-time measurements of transmission and engine oil in helicopters and ground vehicles exposed to extremes of temperature and contamination. It can also measure blood viscosity, thus providing early warnings of heart-attack potential, or can be applied to in-line process control systems in coated paper, petrochemical, plastics, printing, and cosmetics industries.

Contact:Kerem Durdag, Biode Inc. Tel: 207-856-6977, ext. 106 http://rbi.ims.ca/4402-540

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