In the modern world, at work and at home, people are surrounded by electrical appliances. However, in the absence of mains voltage or damage to the wiring, they become useless. To find the cause of the malfunction, a voltage indicator is used. This device is also used to check the condition of electrical networks and equipment before starting repair and installation work.
Content
- Types of devices
- Single pole probe
- Bipolar devices
- High voltage indicator (UVN)
- Universal testers
- Terms of use
Types of devices
Only after making sure that there is no potential difference in the network and on the live parts of electrical machines, you can safely perform any electrical work. Electrical equipment is divided into low-voltage (up to 1kV) and high-voltage (over 1kV). Accordingly, indicators (pointers) are low (UNV) and high voltage (UVV).
Indicators are of two types:
- single-pole;
- bipolar.
Single pole probe
It is used only in AC circuits with voltage up to 1 kV. Requires touching the equipment at one point. The chain closes through the person to the ground. Illumination of the indicator causes a flowing capacitive current.
Designed to test secondary switching nodes. With its help, you can detect the phase in conductors or on the nodes of any low-voltage electrical equipment, including household ones. It is most often used when working with lighting, checking cartridges, switches, phrasing an electric meter.
The most common design is presented in the form of a screwdriver or a fountain pen. Allows you to check the presence or absence of phase voltage. The housing is made of transparent dielectric material. It contains the details of the device:
- pin - screwdriver;
- gas discharge lamp - indicator with ignition threshold up to 90 volts;
- a 1MΩ resistor connected in series provides a safe current value (about 0.5mA), sufficient for the indicator to glow;
- spring - provides reliable contact between all parts;
- finger contact end contact.
This indicator is easy to use. You need to touch the bare part of the conductor or the live part of the electrical equipment with a screwdriver, and touch the end contact with your finger. If there is a potential difference (phase) at this point, the lamp of the device should light up.
The following indicators are produced under the names: INO-70, IN-90, IN-91 and others. The disadvantage of these devices is low sensitivity and susceptibility to interference from adjacent electrical wiring.
Bipolar devices
Can be used in AC and DC operation. In the process, you need to touch two points of the equipment, between which there may be a potential difference. The neon lamp glows when an active current is flowing.
The two-pole voltage indicator consists of two dielectric housings with electrodes - tips. The housings are connected by a flexible, insulated, copper conductor 1 m long. The content of one of the housings is a neon lamp shunted by a resistor. An additional current limiting resistor can be in the same package or in a different one.
The neon lamp glows when a current is generated due to the potential difference between the points of contact with the electrical installation. A current of several milliamperes provides a clear glow - signaling the presence of a phase conductor.
Examples of such two-pole voltage indicators can be models UNN-10K, UN-500, PIN-90M and so on. Such devices are more functional. Unlike single-pole ones, they allow you to check the integrity of the neutral (grounding) wire and determine the line and phase voltage:
- Pointer UNN-10K can operate in AC and DC networks with potential difference from 110 V to 500 V.
- Pointer PIN-90M. Its design and principle of operation are similar to the previous one, but the device can be used in networks with a range from 50 V to 1000 V.
High voltage indicator (UVN)
It is used in switchgears of high-voltage equipment when performing preventive and repair work. It makes it possible to detect a large potential difference, control the phasing.
The most widespread signs are UVN-10 and UVNU-10. The principle of operation is based on the emergence of a capacitive current when the working part of the device is introduced into the electric field of the equipment under voltage. This current excites the glow of the indicator.
Structurally, the UVV consists of three main elements:
- working part;
- insulating part;
- handle with a limiting ring.
Before work, the pointer must be assembled. To do this, unscrew the working part from the insulating part, turn it over and screw it back in. The dipstick should be in place opposite the handle.
Several modifications of such pointers are available. A tip electrode (UVN-10) may be present in the working part for contact with a live node or absent for a non-contact type indicator.
The indicator part is most often combined with the working one and includes light or combined (light and sound) indication (UVNU-10 SZ IP).
Gas-discharge lamps are used for light indication, and in more modern designs - LEDs. Signals, light and sound, must be easily recognized.
The insulating part of the pointer is made of a dielectric with increased dielectric and mechanical characteristics. It must have a smooth surface and be moisture resistant (does not absorb moisture). There should be no scratches, cracks or delamination on it.
Universal testers
Recently, they have gained recognition for their greater functionality. As a rule, these are two-pole pointers. Combined indication - light and sound. Testers allow you to evaluate the magnitude of the potential difference between DC and AC in the range from 12 V to 660 V, as well as to check electrical circuits for an open.
The absence of an open circuit is signaled by a continuous buzzer. In single-pole mode, you can find out the polarity of the DC current and determine the phase for the AC. Light indicators in such devices are high-brightness LEDs. Power supplies - built-in large capacitor or miniature lithium battery.
In parallel with the light indication, an audible alarm (piezoelectric sound emitter) works, which makes working with it safer and more comfortable. An example of such devices - UNNDP-12-660
Terms of use
Getting started with the voltage indicator, you need to make sure its integrity and performance. The potential difference for which it is intended must be higher than the operating voltage of the tested electrical equipment. The date of the next laboratory test of the index should not be overdue.
Before working with the low voltage indicator (UNN), it must be checked for operability. For testing, you can use a connected 220 V socket. A single-pole indicator should determine the phase, and a two-pole indicator should indicate the presence of a voltage of 220 V.
To check the high voltage indicator (HVN), its probe is brought closer to the parts of the electrical installation to which high voltage is applied. The alarm should go off. All operations with UNN must be done with dielectric gloves.
Working on live electrical equipment is associated with a risk to life and health. Pointers belong to the main means of electrical protection and, if used correctly, will ensure safety when working with electrical appliances.
