Cable tester
Encyclopedia
A 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:
In addition to these parts a cable tester may also have a microcontroller and a display to automate the testing process and display the testing results.
A cable tester is used to verify that all of the intended connections exist and that there are no unintended connections in the cable being tested. When an intended connection is missing it is said to be "open" (as in Open circuit
). When an unintended connection exists it is said to be a "short" (as in Short circuit
). If a connection "goes to the wrong place" it is said to be "miswired" (the connection has two faults: it is open to the correct contact and shorted to an incorrect contact).
Generally, the testing is done in two phases. The first phase, called the opens test makes sure each of the intended connections is good. The second phase, called the shorts test makes sure there are no unintended connections.
There are two common ways to test a connection:
There are two common ways to test for a short:
- A source of electric currentElectric currentElectric current is a flow of electric charge through a medium.This charge is typically carried by moving electrons in a conductor such as wire...
, - A volt meter,
- A switching matrix used to connect the current source and the volt meter to all of the contact points in a cable.
In addition to these parts a cable tester may also have a microcontroller and a display to automate the testing process and display the testing results.
A cable tester is used to verify that all of the intended connections exist and that there are no unintended connections in the cable being tested. When an intended connection is missing it is said to be "open" (as in Open circuit
Open circuit
The term Open circuit may refer to:*Open-circuit scuba, a type of SCUBA-diving equipment where the user breathes from the set and then exhales to the surroundings without recycling the exhaled air...
). When an unintended connection exists it is said to be a "short" (as in Short circuit
Short circuit
A short circuit in an electrical circuit that allows a current to travel along an unintended path, often where essentially no electrical impedance is encountered....
). If a connection "goes to the wrong place" it is said to be "miswired" (the connection has two faults: it is open to the correct contact and shorted to an incorrect contact).
Generally, the testing is done in two phases. The first phase, called the opens test makes sure each of the intended connections is good. The second phase, called the shorts test makes sure there are no unintended connections.
There are two common ways to test a connection:
- A 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...
. Current is passed down the connection. If there is current the connection is assumed to be good. This type of test can be done with a series combination of a battery (to provide the current) and a light bulb (that lights when there is a current). - A resistanceElectrical resistanceThe 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...
test. A known current is passed down the connection and the voltage that develops is measured. From the voltage and current the resistance of the connection can be calculated and compared to the expected value.
There are two common ways to test for a short:
- A low voltage test. A low power, low voltage source is connected between two conductors that should not be connected and the amount of current is measured. If there is no current the conductors are assumed to be well isolated.
- A high voltage test. Again a voltage source is connected but this time the voltage is of several hundred volts. The increased voltage will make the test more likely to find connections that are nearly shorted since the higher voltage will cause the insulation of nearly shorted wires to break down.