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Transcript
VOLTAGE DETECTORS - NEON TESTERS - LED TESTERS NEON TESTER (OR VOLTAGE TESTER): • voltage tester, is a simple low cost piece of electronic test equipment used to determine the presence or absence of an electric voltage (usually alternating current (AC) ) in a piece of equipment under test. CONSTRUCTION OF NEON TESTERS : • 1) Metallic Rod and Mouth • 2) Body and Insulation • 3) Resistor • 4) Neon Bulb • 5) Element (Metallic Spring) • 6) Metallic Cap Screw and Clip NEON TESTERS COMPONENTS : WHEN ALL PUT TOGETHER : HOW DOES IT WORK : When we touch mouth of voltage tester with naked Live / hot wire whereas one of our finger touch the metallic Cap Screw or Clip , then circuit is completed and current start to flow in Metallic rod. HOW DOES IT WORK : • It relies on stray capacitance (formed by our body and earth) and current passing through the user's body to complete the circuit. • When circuit is completed, current starts to flow and the filament of neon bulb starts glowing. • This indicates that the touched wire with Voltage Tester mouth is Hot. THEORETICALLY : TWO CONTACT NEON TESTER : TWO CONTACT NEON TESTER : • This type consists of a holder containing a neon lamp and a resistor, the holder is connected with two insulated wire leads. • This type can be used to check for correct grounding or the circuit under test is properly connected and there is no need for direct contact with your body ( safer to deal with ). • It can be used to test voltages in the range of 100-500 volts depending on the value of the resistor . DISADVANTAGES : • The internal construction of the tester provides no protection against shortcircuit faults. • Failure of the resistor and lamp series network can put the user in direct metallic contact with the circuit under test. • Since it relies on capacitance to complete the circuit, direct-current potential cannot be reliably indicated. NON CONTACT VOLTAGE LED TESTER NON CONTACT VOLTAGE LED TESTER : • A non-contact voltage LED tester is an important personal safety device that detects electricity in a wire or outlet, just by getting near it. • It uses the concept of electromagnetics and electronics(transistors hence amplifiers) as a way to work. HOW DOES THE CIRCUIT FUNCTIONS : The front end copper strip forms one side of a capacitor, and then when you bring it near a voltage potential a super tiny current flows between air dielectric of the “cap”. This is mega amplified with the high gain BC547′s and viola, the LED lights up HOW DOES THE CIRCUIT FUNCTIONS : • Since the small bit of current is amplified many times over, the LED lights up even when very small voltages are present. • The battery is used as an additional energy to light the lamp and power the amplifier and does not flow through the user's body. PARTS OF THIS VOLTAGE TESTER : PARTS OF THIS VOLTAGE TESTER : • Nose/probe : This part of the tool houses the sensor which does the detecting. The tip is the correct size and shape to be inserted into plug sockets. • Body : consists of a simple plastic shell which houses the electronic circuit that powers the tool. • on/off button :t is usually a simple press-down button which may require a quick push or holding down for a few seconds. LED VOLTAGE TESTER : - The LED lights up when there is a presence of voltage. - It feels the presence of very low voltages The advantage of this type that there is no need for physical contact with the user’s body. DONE BY : - Khaled Nazzal. - Fahmi abu zaitoun