Ultrasonic Sensors

["rgondzur" <rgondzur@xxxxxxxxx>]

My need is to monitor the perimeter of an outdoor area.
I am considering ultrasonic sensors to act as an intrusion monitor.
They need to be mounted near ground level.

I need a device similar to what I see on upper-priced automobiles that
indicate the presence of items around its perimeter.
I have seen a very nice system mounted on the bumper of a BMW that
works extremely well to indicate a person walking around the vehicle.

The sensor must be designed for outdoor/external applications.

There will be a series of sensors with patterns that overlap to provide
detection around the entire perimeter.
They will all be wired to a controller that will sound an alarm when
the perimeter has been entered.

Perimeter size can vary from one hundred to several hundred feet.

Since they will be used outdoors, what will the issues be?

Therefore, I am looking for low-power, reliable sensors and the
suggested controller to manage the system.

Of course, price will be a determinig factor.