Transcript voltage detectors

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