The sensing circuit develops a larger voltage that turns on a light or sounds the buzzer in the Volt Stick. The sensor tip is a small capacitor coupled to the live voltage. Your hand, body and feet form a relatively large capacitor coupled to the floor. So when you hold the Volt Stick in your hand and place the tip near a live conductor, you are inserting the high impedance sensing element into a capacitively coupled series circuit. The person holding the tester is the first 'plate' of the large capacitor, the ground is the second plate and the person's shoes or carpet is the dielectric between them. The live metallic component (such as a live wire) is the first plate of the smaller capacitor and the other plate is the sensor in the tip of the Volt Stick, the air between them is the Dielectric. This is the basis for understanding how Volt Sticks work. If we have two capacitors in series then a larger voltage will develop across the smaller capacitor. If an AC Voltage is connected across the two conductors, an AC Current will flow across the Dielectric as the electrons are alternately attracted or repelled by the voltage on the opposite plate this makes a complete AC Circuit, even though there is not a complete ‘hard wired’ circuit. To understand this we can turn to electrical circuit theory and look at how a Capacitor behaves.Ī Capacitor has two conductors that are separated by a non-conductor or Dielectric. The voltage, or more correctly the Electric Field, produced by the voltage is detected using the principal of Capacitive Coupling. without any metallic contact) that is without the need for a test probe to touch the wire or surface that is being tested. Volt Sticks detect voltage by a non-contact means (i.e. Volt Sticks may seem very simple and straight forward but many people dismiss them as unreliable because they don’t fully understand how they work. They are very easy to use but, as with any tool, it is important to read the operating instructions and to fully understand the principles behind them so that you know exactly when and where they will (and won’t!) work. Volt Sticks are designed for one very specific purpose - to detect the presence of an AC voltage. Non Contact Voltage Testers go by many names but Volt Stick is the original Non Contact Voltage Tester and the only one to carry the Volt Stick logo.
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