An Electric Fence consists of an open electrical circuit comprising of two arms.
The first arm is the fence connected to the power terminal of the energiser. This section must be totally insulated from any other conductive material (ground, leaves, grass, trees, metal or brick) by plastic insulators or an air gap of at least 3cm. It does not have to loop back on itself and may be a single line away from the energiser.
The second arm is the ground itself that is connected to the Earth terminal of the energiser by way of the earth stake/post.
This then leaves an OPEN electrical circuit (as shown in the diagram) waiting for an errant animal to close it
The Electrical circuit is then CLOSED when the animal (as shown in the diagram) touches both the live fence AND the ground at the same time. This allows the electricity (electrons) to flow from the fence down to the ground and back to the energiser via the earth stake giving the animal an electrical shock as it touches the wire.
The Electric Fence Energiser.
The Energiser is the pulsing heart of the system and operates by converting the input energy (9v, 12v or 220v) into a high voltage (6000v) output charge by way of transformers and capacitors. This output is made safe in two ways, firstly by releasing the flow of electrons from the capacitor in regular pulses of about 1/300th of a second approximately a second apart. The amperage component of the electrical charge is greatly reduced to figures in the range of 15 - 500milliamps. (The majority of units operate in the 100-150milliamp range)*. It is the amperage within the electrical charge and the constant connection that makes electricity dangerous. Compare this with two other scenarios.
Static Electricity when you touch a door, about 30000 volts at 5 milliamps for 1/1000th. of a second, unpleasant but not lasting.
Mains Electricity. 220volts at 13 Amps and constant, unpleasant and regularly causes death.
When the electrical impulse passes through a muscle in the animal it stimulates the muscle to contract. If you haven't touched an electric fence before, the best description of the feeling is like leg cramp but lasting for just a brief moment. By necessity it is very unpleasant so that it provides an effective deterrent when the animal next encounters the fence. The animal remembers the unpleasant experience and avoids touching the wires again. It is NOT some injury or physical damage that produces the discomfort but rather the induced contraction that occurs when a current is passed through muscle tissue. This unpleasant sting (similar to a "thwack" from a riding crop) is what creates a psychological imprint within the animals' brain and it is this that fences him in.
An adequately designed and constructed electric fence works by the combination of a weak physical barrier (the fence) and a strong psychological imprint (the 6000v sting) created in the mind of the animal. This sharp but safe sting then creates a psychological barrier that the animal associates with the fence and discourages it from touching again. Fortunately it only takes one or two animals to be affected and the rest will copy these, called "Socially Conditioned Avoidance"
Never a truer word may be spoken than "A wimpy energiser gives you a wimpy fence."
Whilst the electricity used in Electric Fencing is considerably safer than mains electricity, it should still be used with caution and respect.
* These figures vary between manufacturers and models.
