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Top Tips for Designing with Miniature Sensors

When dealing with sensors that can be as small as a ladybug, it should come as no surprise that there are some unique design challenges.

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Content originally published in partnership with FierceElectronics

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As design engineers continually look to pack more features into smaller footprints, sensors have been consistently shrinking in size. The rise of the Internet of Things (IoT), which is adding intelligence and connectivity to an array of devices and spurring the development of new applications, is now accelerating that trend.

 

IoT applications require the increased use of sensors to collect important information and data from systems, processes, and events, and engineers who are designing these products have one thing in common: They are all looking for ways to pack more functionality into ever-smaller footprints.

 

That has led to innovations in miniature sensors, including the development of multisensor modules and the use of lightweight materials with the mechanical strength and structural integrity that small package sizes need to withstand the rigors of the nastiest of environments.

 

Miniature sensors provide many benefits over their bigger counterparts. But in order for them to perform successfully in an application, their small size dictates that engineers be aware of several considerations when designing with them.

 

To some engineers, these points may sound like nothing more than common sense. And while indeed they are in fact, there are numerous examples of products that failed in the market or were less efficient than they could have been because the designers did not take all of these issues into consideration.

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1. Make sure the sensor is actually measuring what it’s supposed to be measuring.

Many—if not most—designs that call for miniature sensors have small footprints, which means that every component is in close proximity. So, it is important that engineers take extra care to ensure that the intended measurement is actually being taken. Where feasible, the sensor should be directly attached to the target, otherwise the sensor will simply take the measurement from whatever object it happens to be closest to. In some cases, say a design for a thermostat in which the sensor is measuring air temperature, the sensor may likely need to be mounted a reasonable distance away from other components on the PCB. One approach might be to build a moat made of low conductivity material around the sensor and create openings in the enclosure to allow air to flow it.

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2. Be particularly aware of the kind of environment the sensor is expected to operate in, and ensure you adequately protect it.

Material innovations in sensor package have continued apace, which has been instrumental in giving miniature sensors the robustness they need to perform under many different conditions. But the advent of the IoT is now making it possible to put sensors into locations that are even less friendly to electronic devices. Knowing and planning for the type of environment and the conditions that the sensor is expected to operate in help prevent problems later. Will the conditions be hot, dirty, wet, or muddy? What about bumps, vibration, and shock? Could someone accidentally drop the device into a toilet? In some applications, miniature sensors may need some extra protection, which is doable as long as it’s planned for upfront. Also keep in mind that the sensor world is not that simple. A sensor has to connect to two very different worlds--it has to connect to an electrical world, and it has to connect to a physical world in which it measures physical parameters. The two may have very different, even competing requirements that need to be addressed.

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3. Save space by looking for opportunities for the sensors and other components in the design to do double duty.

Could a multi-sensor module do the job? Sensor manufacturers are making great strides in skimping on space and increasing the number of parameters that can be measured by combining multiple sensors into a single, multi-sensor module, which requires less space than using individual sensors. For example, in a module with two sensors to measure relative humidity and temperature, the dew point can also be calculated, resulting in three parameters being measured from just two sensors, all in one package. In order to reduce the overhead required by some electronics, there is also a trend toward outsourcing of the computational needs of the system to the sensor itself. Expect to see more smart sensors, which can analyze signals and make decisions locally based on the results, to hit the market. Some are currently being field tested. In some cases, the packaging might be able to perform double duty, saving on precious space. For example, if the electronics need electromagnetic shielding, the packaging could be made of material that provides both structural integrity and shielding.

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