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Sensors Have to Toughen Up
Factories can be harsh. Sensors have to be robust to survive
Robb Black, Director of Sensor Business Unit, Turck, Inc. -- Design News, August 18, 2003
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Sensors are the backbone of much of design. Here, one expert gives his view of the latest trends and efforts to make sensors hardy enough for the factory floor.
What's the hot topic in sensors today? Robustness. There is a big push to make sensors that can withstand enormous amounts of EMI/RFI.
How do you make sensors more robust? One way is to add filtering capability to get rid of stray signals. We've gone from single-layer to multi-layer boards to include shields and filters so that, for example, a two-way radio near the center won't trigger a sensor.
Doesn't that take up more space and cost more? It does take more space—that's why we go up to four layers—but there is no extra cost to the customer. We use surface-mount technology and our own ASICS to help with board space.
Are there environmental demands that are pushing the industry toward more robust sensors? Absolutely, especially—again—on the factory floor. One example is that sensors have to be able to withstand high-pressure washdowns. NEMA (National Electrical Manufacturers Association) standards require resistance to water, but there is more than water on the factory floor. We test with caustic acids, bases, coolants, and oils because that more closely simulates a factory environment.
Are there any industries that are more demanding than others when it comes to environmental concerns? Naturally, the food industry is most demanding because of their environment. High-pressure washdown with temperature changes make for difficult conditions. We developed our harsh-duty line of sensors for that reason.
Considering how important sensors are in machines, do engineers really understand them? They understand their importance, but they don't think about them early enough in the design process. They don't think enough about the application and the mounting. Engineers think sensors are simple devices, and they don't go to sensor seminars. They go to seminars on what they consider to be more high-technology subjects.
What's the biggest thing engineers need to know about sensors? There are many things, but an important one is to know about the mounting because that can affect how well the sensor works. Too often, it's the mechanical designer who designs where the sensor mounts, but the E/E specifies the sensor. They have to talk to each other.
Is wireless the next big thing in sensors? People certainly are talking about it. Applications could include pressure and temperature transmitters, where there are long runs of cable. But for wireless to take off, battery technology will have to improve.
What's Turck's next big thing? The self-compensating sensor for automotive factories. One sensor will give a maximum range based on how you mount it to metal. Metal around a sensor affects its sensing capability. This sensor compensates for that.
Robb Black has 16 years of experience in sensor technology, including work with inductive and capacitive sensors, ultrasonics, flow, pressure, level detection, rotary, encoders, linear-displacement transducers, and frequency-identification systems.
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