Company insight
Streamlined sensors for seamless integration
Marc Savoie is the vice-president of sales and marketing at SMD Sensors and has more than 40 years of experience supporting many industries in engineering, sales and management roles. Prior to joining SMD Sensors, Marc held positions as business development manager for Harrington Pure, a national distribution firm targeting pharmaceutical and semiconductor companies, as well as product manager for Saint Gobain Performance Plastics, a global materials supply company.
SMD Sensors is replacing its line of ultrasonic flow sensors with a new version. The previous line of flow sensors has been available for more than ten years. Why change? Marc Savoie: The previous version was a two-part system that included a control monitor with touchscreen display plus a separate clamp-on flow sensor. While the technology offered excellent performance, it was designed for lab and research and development applications. SMD’s corporate strategy is to focus on OEM applications, such as medical devices, and it was a challenge to convince customers in this marketplace to integrate the rather large (three -by-five inches) control board that was inside the control monitor into their medical devices. This new version solves this challenge because all electronic features are now inside the small clamp-on sensor housing. By eliminating the need for a separate monitor/control board, SMD can offer its OEM customers significantly easier integration of our sensors into their devices.
How does it work? SMD ultrasonic flow meters use transit-time based technology to measure the volumetric flow of liquid through a tube. Two ultrasonic transducers are positioned at an angle from one another, and a tube is placed between the transducers. A pulse of ultrasonic energy is sent both upstream and downstream. The difference in the time of flight of the ultrasound correlates to the velocity of the liquid in the
tube. The velocity of the liquid can then be used to calculate the liquid’s volumetric flow. In future models, accumulated flow and average sound speed data will also be streamed from the device.
How accurately can the sensor measure flow rate and what are the variables that drive accuracy? Accuracy depends on several variables including tube material, durometer, outer diameter (OD), inner diameter (ID) liquid composition, liquid temperature, ambient temperature, flow rate, and flow regime (laminar/ turbulent). The number of times a user removes and re-inserts the same tube into a flow sensor is another factor. Each application is unique, and we recommend customers provide a sample of their tube to our facility to test to determine the highest achievable accuracy for their application.
Does the ultrasonic flow sensor require the use of any acoustic coupling gel? Due to the design of the tube slot geometry, acoustic coupling gel is typically not required. The sensor works best with pliable plastic tubing; however, the tube slot geometry may be custom designed to work with stiffer tubes.
I noticed on your website your ultrasonic bubble sensors do not need clamping lids, why do your ultrasonic flow meters need them?
The measurement methods between the ultrasonic bubble sensor and
Medical Device Developments /
www.nsmedicaldevices.com
ultrasonic flow sensor differ and, therefore, require different tube slot geometries. The bubble sensors measure the amplitude of ultrasonic energy transmitted across the tube slot, while the flow sensors measure the difference in sound speed upstream and downstream. With the bubble sensors, a simple horizontal compression works well to position the tube appropriately; however, with the flow sensors, a consistent cross-section is needed to repeatably measure the same transit time at a specific flow rate. The additional vertical compression that the lid provides helps to achieve consistent tube placement each time the tube is loaded.
Medical devices are getting smaller and smaller as companies move toward the ambulatory (mobile) and home-device market. How does SMD address requests for limited sensor footprints for medical devices? SMD is very open to customising its designs, particularly for OEM applications where space is limited. For several customers, we have been able to combine multiple sensors into one package such as flow and bubble sensors or flow and occlusion sensors. We can also collaborate with customers to mold features into their device housings and install sensors directly into their device, offering a truly integrated design. ●
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