NPL offers new way of measuring ultrasonic cleaning systems

Published: 20-Aug-2010

NPL has developed a new instrument for measuring the performance of ultrasonic cleaning systems


NPL has developed a new instrument for measuring the performance of ultrasonic cleaning systems said to perform better than current alternatives. The new NPL CaviMeter provides a quick and simple measurement solution for ultrasonic cleaning systems, making quality assurance easier.

Ultrasonic Cleaning Systems are used in many healthcare applications and the medical device manufacturing industry. They work by passing a high frequency sound wave through a liquid detergent to create thousands of small bubbles. These then implode with such force that the impact removes contaminant particles from submerged materials.

The current NHS-recommended technique to measure the performance of ultrasonic cleaning systems uses aluminium foil, which is eroded and punctured by the imploding bubbles. This is an unreliable process to apply and can contaminate the vessel cleaning fluid, adding unnecessary costs.

The new NPL CaviMeter, on the other hand, consists of a sensor connected by a thin flexible cable to a portable monitor and display unit. The sensor is shielded in a special rubber material designed to protect it, and provide it with spatial resolution of a few millimeters.

By monitoring the acoustic signals generated when the clouds of bubbles implode, the CaviMeter identifies how much cavitation is taking place at a given location, allowing equipment to be fine-tuned to produce the ideal quantity and distribution of cleaning action. This approach helps ensure that only the required energy is used, reducing costs and environmental impact.

Mark Hodnett, a Senior Research Scientist at NPL, said: "Until now, there have been no quantitative methods for identifying how much cavitation takes place at different locations in a cleaning system, and therefore no way to ensure that the cleaning process is totally effective. NPL's CaviMeter and sensor can now provide this capability, for both users and manufacturers of cleaning systems. It is the first of its kind for acoustically mapping cavitation produced by ultrasonic cleaning systems used in healthcare."

The CaviMeter supports the manufacture and development of ultrasonic baths, and also allows healthcare organisations to make informed and cost-effective purchasing decisions for cleaning systems. Once a system is chosen, the CaviMeter can be used regularly to test the efficacy of its cleaning performance, even when using different detergents and surfactants (wetting agents that lower the surface tension of a liquid).

The novel spatially-sensitive cavitation sensor was conceived and developed under Strategic Research at NPL, with the accompanying electronics supported by the Measurement for Innovators programme.

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