Continuity tester
Encyclopedia
A continuity tester is an item of electrical test equipment
used to determine if an electrical path can be established between two points; that is if an electrical circuit can be made. The circuit under test is completely de-energized prior to connecting the apparatus.
The tester consists of an indicator in series with a source of electrical power - normally a battery
, terminating in two test leads. If a complete circuit is established between the test-leads, the indicator is activated.
The indicator may be an electric light
or such a device might also be fitted with a buzzer
. This led to the term "buzzing out a circuit" (which means to test for continuity). This term remains in use today, although any sound produced is usually made by the beeper function on a modern digital voltmeter
, but the most simple method that has been used for many years, is a simple curcuit consisting of a 9V battery and a buzzer, with a break in the curcuit to touch what is to be tested at each end to create a complete curcuit and to set off the buzzer if no fault is present.
A popular design has the tester combined with a standard flashlight
. A TRS connector
or jack plug in the rear of the unit permits a set of test leads to be plugged in effecting a quick conversion between the two applications.
For situations where continuity testing must be done on high resistance
circuits, or where delicate conductors and sensitive components that might be damaged by excessive current are present, a low voltage, low current device must be used. These typically use an op-amp and watch batteries to drive an LED
as an indicator. These testers can be exquisitely sensitive; for example they will indicate if the test points are taken by both hands.
There are times when a simple continuity test fails to reveal the problem. For example, vibration-induced problems in automobile wiring can be extremely difficult to detect because a short or open is not maintained long enough for a standard tester to respond.
In these applications a latching continuity tester is used. A more complex device, it detects intermittent opens and shorts as well as steady-state conditions. These devices contain a fast acting electronic switch (generally a Schmitt trigger) forming a gated astable oscillator
which detects and locks (latches) the indicator on an intermittent condition with a duration of less than a millisecond.
To buzz out, a curcuit is usually the first thing that anyone in electrics, when testing cables, will do to locate the break or fault in the connection, and in doing so, see if it is actually the cable or the connecting component that has created the fault.
Electronic test equipment
Electronic test equipment is used to create signals and capture responses from electronic Devices Under Test . In this way, the proper operation of the DUT can be proven or faults in the device can be traced and repaired...
used to determine if an electrical path can be established between two points; that is if an electrical circuit can be made. The circuit under test is completely de-energized prior to connecting the apparatus.
The tester consists of an indicator in series with a source of electrical power - normally a battery
Battery (electricity)
An electrical battery is one or more electrochemical cells that convert stored chemical energy into electrical energy. Since the invention of the first battery in 1800 by Alessandro Volta and especially since the technically improved Daniell cell in 1836, batteries have become a common power...
, terminating in two test leads. If a complete circuit is established between the test-leads, the indicator is activated.
The indicator may be an electric light
Electric light
Electric lights are a convenient and economic form of artificial lighting which provide increased comfort, safety and efficiency. Most electric lighting is powered by centrally-generated electric power, but lighting may also be powered by mobile or standby electric generators or battery systems...
or such a device might also be fitted with a buzzer
Buzzer
A buzzer or beeper is an audio signaling device, which may be mechanical, electromechanical, or piezoelectric. Typical uses of buzzers and beepers include alarm devices, timers and confirmation of user input such as a mouse click or keystroke....
. This led to the term "buzzing out a circuit" (which means to test for continuity). This term remains in use today, although any sound produced is usually made by the beeper function on a modern digital voltmeter
Voltmeter
A voltmeter is an instrument used for measuring electrical potential difference between two points in an electric circuit. Analog voltmeters move a pointer across a scale in proportion to the voltage of the circuit; digital voltmeters give a numerical display of voltage by use of an analog to...
, but the most simple method that has been used for many years, is a simple curcuit consisting of a 9V battery and a buzzer, with a break in the curcuit to touch what is to be tested at each end to create a complete curcuit and to set off the buzzer if no fault is present.
A popular design has the tester combined with a standard flashlight
Flashlight
A flashlight is a hand-held electric-powered light source. Usually the light source is a small incandescent lightbulb or light-emitting diode...
. A TRS connector
TRS connector
A TRS connector is a common family of connector typically used for analog signals including audio. It is cylindrical in shape, typically with three contacts, although sometimes with two or four . It is also called an audio jack, phone jack, phone plug, and jack plug...
or jack plug in the rear of the unit permits a set of test leads to be plugged in effecting a quick conversion between the two applications.
For situations where continuity testing must be done on high resistance
Electrical resistance
The electrical resistance of an electrical element is the opposition to the passage of an electric current through that element; the inverse quantity is electrical conductance, the ease at which an electric current passes. Electrical resistance shares some conceptual parallels with the mechanical...
circuits, or where delicate conductors and sensitive components that might be damaged by excessive current are present, a low voltage, low current device must be used. These typically use an op-amp and watch batteries to drive an LED
LEd
LEd is a TeX/LaTeX editing software working under Microsoft Windows. It is a freeware product....
as an indicator. These testers can be exquisitely sensitive; for example they will indicate if the test points are taken by both hands.
There are times when a simple continuity test fails to reveal the problem. For example, vibration-induced problems in automobile wiring can be extremely difficult to detect because a short or open is not maintained long enough for a standard tester to respond.
In these applications a latching continuity tester is used. A more complex device, it detects intermittent opens and shorts as well as steady-state conditions. These devices contain a fast acting electronic switch (generally a Schmitt trigger) forming a gated astable oscillator
Multivibrator
A multivibrator is an electronic circuit used to implement a variety of simple two-state systems such as oscillators, timers and flip-flops. It is characterized by two amplifying devices cross-coupled by resistors or capacitors...
which detects and locks (latches) the indicator on an intermittent condition with a duration of less than a millisecond.
To buzz out, a curcuit is usually the first thing that anyone in electrics, when testing cables, will do to locate the break or fault in the connection, and in doing so, see if it is actually the cable or the connecting component that has created the fault.
See also
- Cable testerCable testerA cable tester is an electronic device used to verify the electrical connections in a cable or other wired assembly. Generally a cable tester consists of:# A source of electric current,# A volt meter,...
- Continuity testContinuity testIn electronics, a continuity test is the checking of an electric circuit to see if current flows .A continuity test is performed by placing a small voltage across the chosen path...
- LED circuitLED circuitIn electronics, the basic LED circuit is an electric power circuit used to power a light-emitting diode or LED. The simplest such circuit consists of a voltage source and two components connected in series: a current-limiting resistor , and an LED...
- Solenoid voltmeterSolenoid voltmeterA solenoid voltmeter is a specific type of voltmeter used by electricians in the testing of electrical power circuits.Wiggy is the registered trademark for a common solenoid voltmeter used in North America derived from a device patented in 1918 by George P. Wigginton...
- Test lightTest lightA test light, test lamp, voltage tester, or mains tester is a very simple piece of electronic test equipment used to determine the presence or absence of an electric voltage in a piece of equipment under test.-Two-contact test lights :...