In the past, fluid level sensors provided a simple on/off signal, but now sensors are being called upon to supply a great deal more information. The trend toward increased control circuits being employed in both residential and industrial device application monitoring is driving the need for more complex and “smarter” liquid level sensors that are capable of more than just an open or closed signal. In some instances, additional information can be signaled with simple magnetic reed switches by adding many reed switches to a PCB to give multiple liquid level point measurements. In this application, resistors can be placed in circuit to provide discreet voltage outputs that will indicate one of many possible level points along the travel path of a magnetic float.
If a digital signal or custom voltage signal are required by the customer, this is accomplished through the use of either onboard or remote signal electronics. The environment the sensor will be employed can also determine whether a simpler mechanical float sensor will work or if a more sophisticated conductivity sensor is appropriate. A mechanical float level sensor can suffer failure due to contaminants restricting the movement of the magnet containing float. A conductivity sensor must discern between being submerged in fluid or just having a viscous fluid clinging to the probes of the sensor and a standard conductivity sensor that is always submerged in a fluid, is highly susceptible to electrolysis.
Standex Electronics fluid level sensors
Easily customizable and simple to install, reed switch based level sensors are low power devices that don’t require complex electronics, making them very appealing for most applications. For example, dishwashing machines frequently used these sensors to signal an overfill condition to prevent excessive water usage and flooding outside the unit. Another example is a sensor to signal a dangerously low brake fluid reservoir level in automotive applications.
The dishwasher fluid level sensor used a microswitch that had replaced the technology of the R12580/R12581. This product utilized reed switches and a thermistor mounted on a PCB and packaged with an all-in-one piece consisting of two magnet floats. One float and switch provides overflow protection that shuts down the dishwasher, and the other float moves between two reed switches to give multiple level readings.
Over the past few years, customers have begun expecting more from level sensors than just an on/off signal. To provide more information to the user. In addition to dangerous level conditions, customers want warning conditions, and ease of use for convenience. An example is the bulk detergent level sensing feature found in modern laundry equipment. While not required for a dishwasher to function, the sensor prevents the need for the customer from having to check detergent levels every time they run the appliance, providing ‘smart’ feedback and delivering the ease of use and convenience factors customers appreciate.
Environmental trends affecting fluid level sensing
Environmental initiatives are another big driver of new sensor technology and applications, particularly in response to the trend toward closer energy monitoring for both individual and household appliances, and industrial water tanks. There has been a movement towards devices ‘talk’ wirelessly with each other — and we will need a smart sensor between the machine to machine (M2M) interactions, and the medium which they communicate. That’s where Standex Electronics steps in with innovative, high-quality reliable components that fit the bill for such applications. Picture yourself while on vacation receiving a text message from the air conditioner drain line with an alert that the sump pump has stopped working. This type of alert would definitely require a level sensor with onboard electronics. Standex Electronics matters during the moments where the application of sensing such HVAC, appliance, and other products require components that can handle such processes.
Clean water and that of its treatment is another environment trend with huge implications for level sensing. In fact, water treatment in developing nations is perhaps the largest market for level sensors, including applications designed for industrial effluent, sewer water, gray water, and clean water. There is a significant push to be more efficient with the use of water and sensing applications that are being used to ensure that fluid level sensors are not overfilled, causing wastage. Standex Electronics can meet the specifications for the National Science Foundation (NSF) regulations and stainless sensor requirements for various applications as they relate to drinking water, food service, and other related stipulations.
Sensors are being used to provide more accurate feedback on how much water can be reused. This is evident in newer appliance designs, in which engineers are trying to maintain a certain level of water in the wash cycle by using fluid sensors to measure how warm or dirty water is. This lets the sensor determine if water can be reused for rinsing or if fresh water has to be added to the wash cycle and heated. Simply, Standex Electronics products can intelligently provide the functionality necessary to help products be smarter, more efficient, and productive to where the results can be items such as less energy usage, improved resource management, lower costs, and increased performance.
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