Voltage Detectors

Voltage detectors are small portable devices to provide you a quick and inexpensive way to test if there is live voltage on circuits, wires, cables, switches, and outlets before you want to work on them. These devices are also called by various names such as voltage wands or power pens. They are small enough so that you can easily carry them in the pocket of your shirt. Whenever the device detects voltage on any bare wire or even power passing through the insulated wire, it will alert you with audible beeps and blinking lights. These are no-contact devices and safe enough so that you don’t have to touch any live wire during testing for voltage.


The voltage testers offer two levels of voltage testing:



When a voltage above the threshold is detected by the device, they will warn by flashing bright lights and loud audio alarms. Most have a self-test button to verify if the tester is working properly. They are ruggedly designed to operate in the field. Rechargeable batteries and a universal adapter are needed to recharge them.

This type of voltage detectors is designed for non-contact, yes/no voltage detection on electrical wire, switches, and circuits commonly installed in commercial, industrial and domestic buildings. Accidental contact with live wire is not an issue, as the detector is provided with safety features that are appropriately rated for high voltage protection. However, the user must follow safe work practices and wear appropriate personal protective equipment necessary for that environment.

By letting you know if a circuit is live or not before you work on it, is an important and critical safety feature that these voltage detectors provide.  However, you must ensure that you have the right voltage detector for the expected voltages levels you may encounter where you intend to use this device.

You must always verify that the voltage detector is functioning correctly before you attempt any work in the field. You should check the detector by testing it on a known live circuit before you test an unknown circuit. Once you are sure that the device is operating correctly only then use it to check an unknown circuit.

However, if you still have any doubt in your mind about whether the circuit is truly live or dead, use an additional method to check your results.

Most factories are generally CAT III or CAT IV industrial environments. Check if your voltage detector is safety rated for that category and only use it if it is so. Incompatible devices may read the level of voltages incorrectly, giving you the wrong results.

These devices are capacitive voltage detectors and they have certain inherent limitations. Correct detection of voltage depends upon the capacitance between the detector body which is routed through your hand and body to the ground. If this electrical path is not available for any reason, the detector will give incorrect reading. As an example consider a case where you are working, standing on an insulated ladder. In this case, the capacitance between your body and ground will be quite different if you were standing on a concrete floor. This may give you a false reading by the voltage detector.

To avoid incorrect detector readings, you should touch metal that is electrically grounded when you are using the voltage detector. In a series circuit, the smaller the capacitance, the greater is the voltage drop. It is quite possible that there is too much voltage drop from your body to the floor and consequently too little voltage drop across the detector so that you may get a wrong reading. The detector requires to have a certain threshold voltage to turn itself on. In the insulated ladder case, even if the circuit is live,  the detector may not turn itself on. Similarly, if a live conductor is inside a metallic conduit, the detector may not be able to detect the voltage. Always ensure to hold the detector by the body and keep your fingers away from the tip of the detector.

Calibration is a comparison of the equipment’s performance to a standard of known accuracy, and then a correction or adjustment is applied to remove any errors. The benefits of regular calibration are very important. Since this detector is for workers’ safety it must be checked and calibrated regularly.


e2b calibration is an ISO/IEC 17025 accredited calibration laboratory and has the necessary expertise to test and calibrate various types of safety devices including voltage testers. Our verifiable services are unmatched in the industry. We are registered with ANAB. We are also ANSI/NCSL Z540-1-1994 certified. We have the NIST Traceable Wide scope of ISO/IEC 17025 accreditation. Please contact e2b calibration for more information about our on-site services.



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