Energy & Environmental Management Focus on: HVAC 30 | Plant & Works Engineering www.pwemag.co.uk August/September 2024 Used by manufacturers, technicians and field service engineers alike, gas flow sensors can provide crucial insight into the performance of a wide variety of devices. As their applications grow, it’s becoming ever more important to provide gas flow sensing capabilities in a smaller package — but how? Ross Turnbull, Director of Business Development and Product Engineering at ASIC design and supply company Swindon Silicon Systems, explores. In building ventilation and HVAC systems, gas sensors play a crucial role in enabling feedback control and ensuring air is circulating properly. Process industries such as food and beverage and chemical processing can also benefit from the use of gas flow sensors. From a predictive maintenance perspective, gas flow sensors can be useful tools in detecting issues such as clogged filters, leaks and any other blockages. As their applications grow, so does the demand for smaller, more easy-to-integrate sensors. Ensuring these sensors deliver a high performance in an increasingly compact package can be tricky for system manufacturers, but is there a solution? Exploring flow sensors First, let’s delve into the basic principles of a gas flow sensor. A common type of gas flow sensor is the thermal flow sensor, sometimes referred to as the “hot wire” type. The principle is simple. A “heater” element sits in between a pair of thermopiles. When there’s no airflow, the temperature distribution around the heater is symmetrical. But when air does flow across the sensor, it causes a noticeable change in the temperature distribution, with one side now warmer than the other. It's important to choose the right materials for the sensor to function correctly. When it comes to the wire, it’s preferable to choose a material with a high temperature coefficient of resistance, such as platinum or a nickelchromium alloy. Higher coefficients equal a higher increase in electrical resistance for a given rise in temperature, thereby making The importance of accurate gas flow measurement
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