How low-power overmolded reed switches solve vexing position sensing challenges
sensing and switching to take place at a relatively large distance and need a higher sensitivity device. Reed switches with lower sensitivities are best suited if the application requires a short activation distance. If the switch is too sensitive, it can experience false triggering from stray magnetic fields or vibrations. If the switch is not sensitive enough, it might not activate when needed. In either case, system reliability suffers. The basic parameter related to sensitivity is ampere-turns (AT) that measure how close a magnet needs to be to trigger a switch. A low AT indicates a higher sensitivity, and the switch will activate with a weaker magnet of over a greater distance. A high AT switch needs a stronger magnet or closer proximity for operation. Littelfuse specifies three parameters related to sensitivity. The pull-in AT range measured before molding and modification of the AT. The activate distance range in mm. The deactivate distance range in mm. The 59177 series offers three sensitivity options denoted by "S", "T", and "U", that correspond with models, 59177-1-S-00-D, 59177-1-T-00-D, and 59177-1-U-00-D, respectively (Table 1).
with thermal expansion.
know that security devices aimed for use in homes can experience high levels of shock and vibration. The 59177 series excel in those applications as well. The compact size and no leakage current when open in standby, plus zero operating power consumption
The overmolded design provides excellent mechanical shock and vibration resistance, making it suitable for applications where the switch may experience mechanical stress. You can design these switches into applications with up to 100 G of shock and 30 G of vibration, as specified in EIA/NARM RS-421-A and MIL-STD-202. The hermetically sealed, magnetically operated contacts ensure reliable operation and protection from the environment. Hermetic sealing also improves switch operation by protecting the contacts from dust and other pollutants that can interfere with the operation of unsealed mechanical or optical switches. Finally, the hermetic sealing makes them suitable for use in explosive atmospheres where even tiny sparks from conventional switches constitute a hazard. The 59177 series is certified to European standard ATEX (ATmosphères EXplosibles) II 3 G Ex nC IIC Gc. The ability to operate in harsh environments makes the 59177 series suitable for a wide range of applications. Of course, the ATEX rating can be needed in industrial settings, but if you’ve ever experienced a door or window slammed shut in a residence, you
of these switches bring huge benefits to battery-powered applications that may never
experience harsh shock or vibration, like tamper protection for meters, proximity and limit sensing in small consumer appliances, and some types of process control equipment. While the general specifications make these reed switches suited for a wide range of applications, the ability to select from several sensitivity levels makes it simple for you to optimize performance
for specific design and packaging requirements.
Sensitivity selection Being able to select the
sensitivity of reed switches is a crucial specification since it determines the activation distance and reliability of the switching action, important considerations to ensure optimal performance based on your specific application demands.
Some applications require
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