A capacitive sensor will be adversely affected by weather, rain, water, etc.

A metal detector WOULD work, but you will need to install a non-metallic cover
to protect from water as well, but it could be potted (A larger  
version is buried in concrete or asphalt and used to detect when cars  
are at a
ticket dispenser; these have an almost unlimited lifetime). You would need
to have a plate that would move down slightly when body weight steps  
on it, and
so detected by an RF metal detector as a change in frequency (changing  
the inductance, i.e. the tuned loop).

--Bob



Quoting alan smith <micro_eng2@yahoo.com>:

> wow...couple of ideas I hadn't thought of..so thanks!  The only one   
> I was thinking was using an accelormeter, where its used more of a   
> vibration sensor.
>
>   In as much as analyzing the mode of failure, the orignal failure   
> was from a close proximity lighting strike, and not sure on the   
> second since I just sent the failed unit back to the design house.   
> They may not want to replace it with something more robust or less   
> prone to failure but the biggest problem I have with the design is   
> its transmitting over cat5 analog voltages from the load sensor to   
> the interface, so losses in the cable, broken cable, poor   
> connections all can affect the system.  I'd rather just see an   
> on/off signal to the control with the local A/D sending it.  But in   
> the end im just the fixit guy for this project.
>
>   I've sent an email to the end user asking to describe what isnt   
> working exactly.  Of course I expect an answer...it doesnt activate   
> when stepped on....hmmm...guess its broken.  I'd rather not make too  
>  many trips to site, waste of time and fuel (but I charge these guys  
>  mileage at least)
>
>
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