Electrical testers are devices designed to test the presence of, rather than measure, electrical conditions. These testers can range from very simple instruments that signal that voltage is
present in a circuit, to more complex instruments featuring multiple testing options for high-voltage applications.
Electricity is, perhaps, the one common denominator in industrial, commercial and residential settings. It is the power that runs the motors, brightens rooms, controls the temperature, etc.
Potentially, it is also very dangerous. Testers provide a quick and easy way to verify electrical conditions, often with just a simple audible or visual cue, prior to the repair or maintenance
of a live circuit.
Though there are other instruments, such as multimeters, capable of doing the work of most testers, the simplicity and low cost of testers makes them a crucial component in the toolboxes of
electrical technicians.
Types of Electrical Testers
Voltage Tester
Voltage testers are used to determine the presence or absence of voltage in a piece of equipment under test. Voltage testers are generally specific to AC or DC voltage. Most are suitable for
either line-voltage or lower-voltage ranges though some are intended for mains-voltage detection.
Often in pen form, voltage testers are basically just an electric lamp connected with one or two insulated wire leads. They are inserted into a power receptacle where the presence of voltage at
the receptacle will light the lamp (or another indication, depending upon the type of tester). It’s often desirable to test outlets multiple times to make sure it has been done correctly and that
test results are accurate.
In addition to the contact voltage tester, some are designed as non-contact. These rely on detecting capacitive current, the changing current field around energized objects, and require no direct
contact with the circuit. Some non-contact voltage testers are amplified which provides stronger or weaker indication intended to gauge the relative strength of the detected voltage thus providing
clues about the location of an energized object.
Circuit Testers
Circuit testers are devices for testing AC outlet load handling capabilities plus outlet tester functions as a way to determine whether or not a circuit is good. Generally consisting of two leads,
the device works by touching one lead to a live wire and the other to a neutral or ground. Doing so will trigger a light or sound indicating that the power is on and the circuit is good. If the light
or sound is not triggered, either the power is turned off or the circuit is bad.
Circuit testers are especially handy in older homes when it’s important to know if an equipment ground wire is actually connected to ground elsewhere in the system. It may be necessary to perform
this check when replacing older ungrounded switches with grounded ones as now required by the National Electrical Code.
Continuity Testers
Continuity testers are designed to determine if an electrical path can be established between two points. The test is completed with the power to the circuit turned off. This is a much safer
alternative than trying to trace wire routes by testing energized circuits.
Continuity testers consist of an indicator in series with a source of power, usually a battery, a probe and a test lead. When the probe and lead are touched to any continuous conductive path,
usually a wire, a circuit will be complete and the indicator will be activated. The indicator is usually a light or, more commonly, a buzzer. This has led to the term "buzzing out a circuit" to
mean testing for continuity.
Continuity testers are a great help for not only determining if a circuit is complete but also for testing whether or not a switch is working and locating a specific wire in a bundle.
Appliance Testers
Appliance testers are much more sophisticated instruments than the typical “two leads and a bulb” testers used for voltage and continuity tests. Appliance testers combine common tests used to
ensure the safety of electrical appliances and tools.
Old or poorly maintained electrical tools and appliances can become a safety hazard, potentially causing injury to personnel. Regularly testing electrical equipment is a safe practice against
costly repairs, and may reduce liability.
There is no standard set of tests included with tool and appliance testers. Most however, include some combination of the following:
- Earth bond and continuity tests
- Insulation test
- Touch current test
- Differential leakage test
- Substitute / alternative leakage test
- Functional load test
- Extension and IEC power cords
- Hi-pot flash test
High Pot Testers
The name high pot tester, alternatively called hipot, is based on an abbreviation for high potential. This includes a class of instruments used to verify electrical insulation in devices
that could produce an electric shock if it failed. High post testers are important electrical safety tools used on finished appliances, cables or other wired assemblies, printed circuit boards,
electric motors, and transformers.
Normally, all electrical devices leak some amount of current due to the voltages and internal capacitance present within the item. Sometimes, because of design flaws or simple wear and tear,
the insulation in the product breaks down which can result in excessive leakage current flow. This can cause an electrical shock severe enough to injure or kill.
A high pot test verifies that the insulation of a product or component is sufficient to protect the operator from electrical shock. Typically, the high pot test involves applying high voltage
between an item’s conductor and its metallic shielding. Any current that leaks through is monitored and measured by the tester. The results of this test imply that if a deliberate application of
too much voltage doesn’t cause the insulation to break down then normal operating voltages will be safe. High pot testers can also help find material and quality defects such as small gap spacings
between current-carrying conductors and earth ground which can cause electrical shocks.
Various models of high pot testers use slightly different variations of testing. The various tests differ in the amount of voltage applied and the amount of acceptable current flow.
Phasing Testers
Phasing testers are used on grounded and ungrounded alternating current systems to check high-voltage fuses, test for correct phase connections and test for the absence of high voltage on
de-energized lines or apparatus.
Phasing testers consists of two insulated fiberglass poles, one with a length of insulated cable stored on a reel and the other with a display module. Each pole has end fittings used for
interchangeable probes. When testing, the cable is attached to the display and both poles are used to touch the probes to the appropriate conductors for making phase-to-phase or phase-to-ground
voltage measurements.
Applications for phasing testers include absolute phase-angle identification, mapping and tagging, transmission phasing, distribution phasing, secondary phasing, capacitive test-point phasing,
mobile substation phasing, all general phasing, CW/CCW phase sequences, URD and overhead, and flag delta/wye or wye/delta transformations
Phase Rotation Testers
Phase rotation testers are used to determine the rotation direction of polyphase electrical systems to ensure equipment is connected properly to the mains power supply. Polyphase electrical
systems, usually 3-phase, are common in industrial settings to efficiently and economically satisfy the massive electrical needs of the large motors found in such settings.
When a 3-phase motor is connected to a 3-phase electric circuit, inadvertently reversing two of the motor’s stator leads will reverse the rotating magnetic field within the motor and cause
the motor to also run in reverse. Though some motors may run with incorrect phasing, others, like hydraulic pumps, cooler units or coolant pumps may sustain significant damage if run in reverse.
Phase rotation testers can help save you from the cost and embarrassment or wiring a motor backwards. The testers are available in many styles with an assortment of features, but the basic idea
is that they indicate the phase sequence or phase rotation of a three-phase system and whether each of the three phases is live or not. Such information will confirm whether or not equipment is
wired correctly.
If you have any questions regarding electrical testers please don't hesitate to speak with one of our engineers by e-mailing us at sales@instrumart.com or calling 1-800-884-4967.
