March 23, 1998 Design News
Proximity switch reduces downtime
by Rick DeMeis, Associate Editor
"The number one cause of proximity switch failure
is physical contact with the target," notes Roger
Varma, product manager for efector (Exton, PA). "With
extended range and a setup LED, quadronorm plusTM
switches will significantly reduce those failures."
Here's how these inductive proximity switch improvements
are realized. Optimized geometry and core material give
twice the range of conventional switches. Thus a target
is detected farther away, precluding contact. A separate
yellow setup LED, which lights to indicate nearing an
unstable condition, more accurately positions the switch.
For instance, with a flush-mounted switch, when the
target is between 80 and 100% of the range, both the
yellow setup and red output LEDs light to indicate marginal
sensing conditions. With nonflush-mount units, the setup
LED illuminates if the target is in the 100 to 115%
range, where slight changes may trigger a switch.
When designing the quadro-norm plus, efector talked
to maintenance people about technology that would make
the proximity switches more productive. Their dc installation
can be "flipped" for normally open or closed
switching. Either type can be done with positive or
negative switching, giving a total of four output functions.
Thus, stocking of different units is reduced by 75%.
And with ASIC programmability, setup time and inventory
requirements are further eased.
The switches come in one-piece housings in threaded
metal bodies 12, 18, and 30 mm in diameter. Flush-mountable
sensing ranges are 4, 5, and 15 mm; nonflush-mountable
7, 12, and 22 mm.