Fitter's probe. Scheme, description

Free technical library

ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
Free library / Schemes of radio-electronic and electrical devices

Fitter's probe. Encyclopedia of radio electronics and electrical engineering

Free technical library

Encyclopedia of radio electronics and electrical engineering / Measuring technology

Comments on the article

When looking for faults in the network or repairing electrical appliances, most electricians usually use a primitive "control" or, at best, a megohmmeter. And how each of them needs easy-to-use, small-sized and reliable probes or testers in their work. We invite you to familiarize yourself with one of them, a universal indicator probe.

The device can check the electrical circuit and separately its elements - diodes, transistors, capacitors, resistors; make sure that there is AC and DC voltage from 1 to 400 V; detect the phase and "neutral" wire of the network; perform phasing in AC and DC circuits; evaluate the insulation resistance of electrical equipment.

fitter's probe

The device is a DC amplifier on transistors VT1, VT2 (see schematic diagram Fig.1). Resistors R1, R3 limit the base currents of the triodes. Capacitor C1 creates a negative feedback circuit for alternating current, excluding false indication from external pickups. Resistor R4 in the VT2 base circuit is used to set the required resistance measurement limit, R2 limits the current when the probe operates in AC and DC circuits. Diode VD1 rectifies the alternating current.

In the initial state, the transistors are closed, and the HL1 LED does not light up, but if the probes of the device are connected together or connected to a working electrical circuit with a resistance of not more than 500 kOhm, then the LED lights up. The brightness of its glow depends on the resistance of the circuit under test - the larger it is, the lower the brightness.

When the probe is connected to an AC circuit, the positive half-waves open the transistors and the LED lights up. If the voltage is constant, the LED will light up when there is a “plus” of the source on the X2 probe.

The device can use silicon transistors of the KT312, KT315 series with any letter index, with a value of P21e from 20 to 50. You can also use pnp conductivity transistors by changing the polarity of the diodes and power supply. Diode VD1 is better to install silicon brand KD503A or similar. LED type AL102, AL307 with ignition voltage 2-2,6 V. Resistors MLT-0,125, MLT-0,25, MLT-0,5. Capacitor - K10-7V, K73 or any other small-sized one. The device is powered by two A332 elements. You can use other sources, but the dimensions of the probe depend on them.

It is better to configure the device on a temporary circuit board, excluding resistor R4 from the circuit. Connect a resistor with a resistance of about 500 kOhm to the probes to set the upper limit for measuring resistance, while the LED should light up. If this does not happen, the transistors must be changed to others, with a large coefficient h21e.

After the LED lights up, by selecting the value of R4, achieve the minimum glow at the selected limit. If necessary, other resistance measurement limits can be entered into the device by changing them using the switch. Probe X2 is fixed on the body, and X1 is connected to the device with a stranded mounting wire with a cross section of 0,8 mm2. The latter can be made from a collet pencil or used ready-made from an avometer.

Now about working with the device. The serviceability of diodes and transistors is checked by comparing the resistances of pn junctions. The absence of glow indicates a break in the transition, and if it is constant, the transition is broken. When a good capacitor is connected to the probe, the LED flashes and then goes out. Otherwise, when the capacitor is broken or has a large leak, the LED is constantly on. Thus, it is possible to check capacitors with ratings from 4700 pF and higher, and the duration of the flashes depends on the measured capacitance - the larger it is, the longer the LED burns.

When checking electrical circuits, the LED will only light when they have a resistance of less than 500 kOhm. If this value is exceeded, the LED will not light.

The presence of alternating voltage is determined by the glow of the LED. With a constant voltage, the LED is lit only when there is a "plus" of the voltage source on the X2 probe.

The phase wire is determined as follows: the X1 probe is taken in hand, and the X2 probe touches the wire, and if the LED is on, then this is the phase wire of the network. Unlike the neon indicator, there are no false positives from external pickups.

Performing phasing is also not difficult. If the LED lights up when the probe touches the wires with current, it means that the probes are on different phases of the network, and if there is no glow, they are on the same one.

The insulation resistance of electrical appliances is checked in this way. One probe touches the wires, and the other the body of the electrical appliance. If the LED is on, then the insulation resistance is below normal. The absence of glow indicates the serviceability of the device.

Using a probe, you can also detect malfunctions in electronic devices, since, by combining the functions of three different devices, it serves as the simplest tester.

Author: V. Rumyantsev

See other articles Section Measuring technology.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

The world's tallest astronomical observatory opened 04.05.2024

Exploring space and its mysteries is a task that attracts the attention of astronomers from all over the world. In the fresh air of the high mountains, far from city light pollution, the stars and planets reveal their secrets with greater clarity. A new page is opening in the history of astronomy with the opening of the world's highest astronomical observatory - the Atacama Observatory of the University of Tokyo. The Atacama Observatory, located at an altitude of 5640 meters above sea level, opens up new opportunities for astronomers in the study of space. This site has become the highest location for a ground-based telescope, providing researchers with a unique tool for studying infrared waves in the Universe. Although the high altitude location provides clearer skies and less interference from the atmosphere, building an observatory on a high mountain poses enormous difficulties and challenges. However, despite the difficulties, the new observatory opens up broad research prospects for astronomers. ... >>

Controlling objects using air currents 04.05.2024

The development of robotics continues to open up new prospects for us in the field of automation and control of various objects. Recently, Finnish scientists presented an innovative approach to controlling humanoid robots using air currents. This method promises to revolutionize the way objects are manipulated and open new horizons in the field of robotics. The idea of controlling objects using air currents is not new, but until recently, implementing such concepts remained a challenge. Finnish researchers have developed an innovative method that allows robots to manipulate objects using special air jets as "air fingers". The air flow control algorithm, developed by a team of specialists, is based on a thorough study of the movement of objects in the air flow. The air jet control system, carried out using special motors, allows you to direct objects without resorting to physical ... >>

Purebred dogs get sick no more often than purebred dogs 03.05.2024

Caring for the health of our pets is an important aspect of the life of every dog owner. However, there is a common assumption that purebred dogs are more susceptible to diseases compared to mixed dogs. New research led by researchers at the Texas School of Veterinary Medicine and Biomedical Sciences brings new perspective to this question. A study conducted by the Dog Aging Project (DAP) of more than 27 companion dogs found that purebred and mixed dogs were generally equally likely to experience various diseases. Although some breeds may be more susceptible to certain diseases, the overall diagnosis rate is virtually the same between both groups. The Dog Aging Project's chief veterinarian, Dr. Keith Creevy, notes that there are several well-known diseases that are more common in certain breeds of dogs, which supports the notion that purebred dogs are more susceptible to disease. ... >>

Random news from the Archive

Samsung Gear VR Innovator Edition - virtual reality glasses for smartphones 24.06.2015

Samsung Electronics announced the start of sales of the updated virtual reality glasses Samsung Gear VR Innovator Edition, fully optimized for the new generation smartphones Samsung Galaxy S6 and Samsung Galaxy S6 edge.

Samsung Gear VR Innovator Edition is designed specifically for the flagship smartphones Samsung Galaxy S6 and Samsung Galaxy S6 edge with their 5.1-inch Super AMOLED screens and opens up new possibilities for entertainment and high-definition multimedia content. With reduced pixelation, a wider field of view, and longer runtimes, users will be able to experience VR in a new way, Samsung says.

The updated model of Samsung Gear VR has become 15% smaller. Ergonomic fixing straps and mechanical ventilation provide comfortable use, while greater processing power and improved graphics quality allow users to enjoy cutting-edge virtual reality content. In addition, the operating time of the device can be extended due to the possibility of power supply via USB.

The Samsung Gear VR Innovator Edition will go on sale June 18th. The recommended price is $275.

Other interesting news:

▪ Snapdragon 665, Snapdragon 730 and Snapdragon 730G mobile platforms

▪ Artificial analogue of the sucker of a fish-stick

▪ Affordable Antec Power Supplies with 80 PLUS Platinum certification

▪ New Fiber Speed Record

▪ Plant Based Chicken by KFC

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ section of the website Experiments in Physics. Selection of articles

▪ article to the Modeller about the helicopter. Tips for a modeller

▪ article Which fish is the fastest? Detailed answer

▪ article Project Manager. Job description

▪ article Kvasovanie sheepskins. Simple recipes and tips

▪ article Unsoldering the interface cable for Siemens phones. Encyclopedia of radio electronics and electrical engineering

Leave your comment on this article:

All languages of this page

Home page | Library | Articles | Website map | Site Reviews