What is an electric fence?
An Electric Fence is a complete alarm system with the additional deterrent feature, of being capable of inducing a no lethal,high voltage shock to illegal intruders. The energizer that powers the system produces a high voltage pulse (6000 to 10000 volts) with very low amperage (where lays the potential danger to the human body).
The energizer has a back up battery that maintains the system running even when the main 110 volts source is cut.
The back up rechargabe battery can support the system for about 48 hours or more unless the alarm is continuously active, since the sirene feeds from the back up battery, it drains it very quickly if the alarm is constantly on. In the event of an emergency when main power will not be available for longer periods, a high amperage battery normally used on automobiles, can maintain the system running for longer periods since the energizer`s power consumption is very low.
The ideal voltage on the fence is between 7000 to 8000 volts. A System running 15 thousand volts is not better for having a higher voltage. The non lethal pain it inflicts on the intruder is the same at 7000 thousand volts as it is at 15 thousand. On the other hand, the higher the voltage the more sparks the system will produce with the potential risk of setting a false alarm . Good grounding of the system is pivotal for its correct operation, protects the energizer and assures a good quality electric shock on the intruder.
What affects the electric shock effect on the intruder?
How does it work?
When the intruder touches the wires (not all of them are live) the body receives a painful no lethal electric pulse (not continous current)
False alarms are almost inexistent. The system requires the setting off of three pulses –or more- to turn on; this way, if a cat or another animal touches the Electric Fence® this will not trigger the alarm given that only one pulse would have been lost.
Energizer: It is the equipment that provides energy to the system: It comes within a metallic o plastic box that generally is installed somewhere near the protected perimeter , keeping it away from the reach of children usually in a waste room, laundry room, security booth, etc…
Grounding: A good grounding is essential for the proper functioning of the Electric Fence®. This is made either with a copper or galvanized bar, depending on the equipment specifications. Two bars is the standard but in large perimeters more grounding is needed sometimes.
Lines: The wiring of the fences alternates positive and negative.. Low voltage is used to wire zoning cards (not all energizer models have this capability, please check) if the perimeter size or security conditions, requires it. The number of lines (seen vertically) may vary from a minimum of 2 to up to 26 or 30 lines.
How to keep tension in the lines
Enérgico S.A. uses Gripple® for wire tensioning (www.gripple.com.uk) , a very ingenious device that keep lines tense, also used to fix any ruptures and assure that the Electric Fence wire is tense at all times, “like a guitar`s string ”.
Connections between two sections of the fence when there is a level change or an increase or decrease of the number of lines .
Output and Return
The energizer sends the high voltage pulse to the fence, it goes around the perimeter and return from the fence to the energizer. Some of these systems have a microchip that “learns” what the normal conditions of each installation are, a minimum – but normal – variation may not activate the alarm . But a sudden loss of three pulses trigger it (three seconds of electric flow interruption). Similar systems defend Israel’s border with its neighbor countries. This way an intrusion can be detected as well as manipulation attempts. Some models admits being zoned, (justified only for big perimeters) monitoring both high lines as well as the neutral lines. Other models can be programmed using a keyboard to select voltage level and time of activation , only alarm mode or alarm + high voltage mode.