The bane of all limit switches is water.  Most are “rain tight,” “water resistant,” etc.  However, a steady head of water will eventually permeate the switch and corrode the contacts.  Optical sensors, like LightLOC, are relatively immune to the effects of water, and LightLOC sensors are encapsulated in a very durable coating to seal them against a head of standing water for added protection.  However, should water at a high pressure force its way into the sensor, the components are highly immune to corrosion.  All the mechanical components are fabricated from plated aluminum, or stainless steel.  .

It’s an unfortunate byproduct of all monitoring systems that the fiber, or copper, connecting the sensor to a central monitoring point is going to be damaged, sooner or later.  Detecting damage to the copper wires leading to and from a limit switch is problematic.  If the switch is “normally open” a break in the wire cannot be detected.  If the switch is “normally closed,” the break is detected as the switch being tripped.  Basically, someone has to go out and confirm that the switch is working and then find the damage and fix it.  Finding a break in an electrical wire somewhere on its 3000 foot length presents the obvious challenges.  Certainly, the optical fiber connecting a LightLOC sensor can be cut by accident or malice.  However, the OTDR at the central monitoring point of a LightLOC system provides two critical advantages.  First, the break will always be seen.  A reflective spike caused by a fiber break is recognized by the monitoring software.  Second, the location of the break is immediately known.  In the typical system, a break is located to within a few meters.

The susceptibility of copper wire to tampering is easily understood.  By either cutting a wire, or splicing a jumper around a switch, the switch can be shown as open or closed, respectively.  Thus its functionality is gone.  Attempts to cut optical fiber are immediately detected and the location calculated to an accuracy of a few meters on most systems (±10 meters in the worse case).  Attempts to splice into the fiber are seen as reflection changes in the system and this will also trigger an alarm.  Resistant to EMI, lightning, and RF, electrical switches are susceptible to electrical disturbances in their environment.  Fiber-based sensors, like LightLOC are inherently immune to electrical disturbances.  No shielding or special enclosures are required.  This property contributes to the lower false alarm rate of optical sensors.  In summary, the table below reflects an accurate comparison between a LightLOC system and limit switches:

Conclusion: The limit switch has been monitoring the presence, or absence, of things for decades. And it will remain useful for that task. However, when a long range, corrosion resistant, more robust sensor is needed, LightLOC fills the bill.