Universal probe. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Measuring technology

 Comments on the article

Those who are engaged in repairs or just radio amateurs know how often it is necessary to check semiconductors for the integrity of pn junctions. This usually doesn't cause problems. But look at how it's done. We turn on the tester, set it to the desired mode of operation, holding both the probes and the transistor under test with our fingers, connect "+" to the base, "-" to the collector, read the readings, then "-" to the emitter, look at the tester again, after that everything is vice versa . The transistor will slip out of your hands a couple of times during the test. You can try to put it on the table and "feel" there, or try to use "crocodiles" instead of probes (you have to manage not to close the transistor leads with them) - all this is no better than the first option. This also includes a lot of dialing of other elements, such as fuses, low-resistance resistors, acoustic emitters, etc.

Solution to the problem: probe. Simple, convenient.

Look at the well-known scheme:

We connect the tested diode or transistor junction to the contacts in the form of 2 plates. One of the LEDs lights up depending on the direction of the transition. Both light up - the transition is broken, none of them light up - a break. Thus, the diode is checked by one touch of the leads to the probe contacts, the transistor - by two or three (it is also advisable to check the absence of a short circuit between the collector and the emitter).

Change the power source to autonomous:

Or another option:

See also "Radio" 1995, No. 6, p. 28 (A. Karabutov. "Test of semiconductor devices"); 1999, no. 9, p. 51 (G. Chagin. "Probe for checking pn junctions").

The basis of all of them is a generator with a frequency of several tens of Hz with a paraphase output.

Each of the schemes shown in the figures has its own advantages and disadvantages for using them in a probe. The first one has a low output current at a supply voltage of 3 V. It can be solved by using super bright (low power) LEDs. However, even in this case, when, for example, LEDs ring, the total voltage drop in the circuit will be too large and the current through the LEDs will approach zero. Increasing the supply voltage sharply increases the current consumed by the generator. The second circuit has a fairly large output current, but the current consumption in standby mode reaches 60 μA, which will require the use of a power switch when using "clock" elements (G-8, LR-43, LR-44, etc.). And this is an additional inconvenience.

Due to the complication, we obtain a circuit with the required parameters:

A generator is built on the elements DD1.1, DD1.2. DD1.3 and DD1.4 are used as an inverter with increased load capacity. Transistors VT1, VT2, when XP1 and XS3 are closed, open alternately, respectively, HL1 and HL2 light up in their collector circuits. Since this happens at a frequency of several tens of Hz, their glow seems to be continuous. If a VDx diode is connected to the specified contacts, for example, in the same polarity as shown in the diagram, only HL2 will glow.

XS2 is used to determine the polarity of voltage sources with a level from 1 to tens of V. When a positive voltage is applied to XP1 relative to XS2, HL1 lights up, negative - HL2, variable - both LEDs.

XS1 is used to test capacitors from fractions to several hundred microfarads. When Cx is connected, as indicated in the diagram, HL1 lights up, after the capacitor (healthy) is charged, it goes out.

Resistor R1 together with R4 determines the input impedance of the probe, which allows you to change its sensitivity. When moving the resistor slider to the left according to the scheme (increase in resistance):

• sensitivity to reverse currents increases and forward current decreases when testing semiconductors;
• increases the sensitivity of the input to determine the polarity;
• increases the charging time when checking capacitors.

By the moment the LEDs light up when the R1 engine rotates, you can estimate the voltage value or resistance of the ringing circuit (resistor), and by counting the HL1 burning time when checking capacitors, you can estimate their capacitance.

Additionally, the probe can be used for:

• for continuity of circuits with a maximum resistance of 3 - 6 kOhm to 30 - 50 kOhm in different positions of the R1 slider and for estimating the resistance of resistors;
• estimating the capacitance of capacitors by the brightness of the LEDs when connected to XP1 and XS3. Range - from several thousand pF to fractions of a microfarad at different positions of the resistor R1 slider;
• check acoustic emitters (speakers, telephones, etc.) by ear by connecting them to XP1 and XS3;
• check the signal flow in the AF amplifiers (and even the 455/465 kHz IF, since the harmonics of the probe generator square-wave pulses extend to hundreds of kHz). XP1 and XS3 are also used. The signal should be applied through an isolation capacitor 0,1 - 1 μF;
• check the operation of the IR remote controls. To do this, you need to connect a photodiode to XP1 and XS3 (a phototransistor is even better). The remote control should be kept at a distance of a few cm from the photodiode. At the time of pressing the buttons of a working remote control, you can observe the flickering of one of the LEDs of the probe (the other can glow constantly).

There are no critical parts in the probe. Everything depends on the requirements. You can make it in the form of a small probe or even a bracelet using surface mount elements, build it into a frequently used measuring device (tester), etc.

Transistors can be replaced with KT315 / KT361 or KT3102 / KT3107. LEDs - any, if their brightness is sufficient at a current of 0,5 mA (for example, KIPD-05A). The K564LA7 chip can be replaced with the K561LA7. Resistor R1 type SP3-41. In addition to its small size (diameter 8 mm), it also has digitization on the adjusting dial. Sockets XS1 - XS3 - contacts from lamp panels. As a power source, you can use almost any "clock" cells or one 3-volt lithium cell. The current consumed by the probe in standby mode is 6 - 7 μA, in operating mode 0,5 - 1,5 mA, so, for example, elements of a size of 7,9 * 3,6 mm (STs-21) will last several months.

Similar probes, made according to different schemes, have been used by me since 1993. Here is another one, more complex, but providing more LED current:

If there is a slight illumination of the LEDs in standby mode, a capacitor with a capacity of about 1 pF should be connected between the bases and emitters of transistors VT2, VT100.

The figure shows one of the design options for the probe.

Author: Khafizov Razil, elec@udm.net, Sarapul, Udmurtia; Publication: cxem.net

See other articles Section Measuring technology.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Machine for thinning flowers in gardens 02.05.2024

In modern agriculture, technological progress is developing aimed at increasing the efficiency of plant care processes. The innovative Florix flower thinning machine was presented in Italy, designed to optimize the harvesting stage. This tool is equipped with mobile arms, allowing it to be easily adapted to the needs of the garden. The operator can adjust the speed of the thin wires by controlling them from the tractor cab using a joystick. This approach significantly increases the efficiency of the flower thinning process, providing the possibility of individual adjustment to the specific conditions of the garden, as well as the variety and type of fruit grown in it. After testing the Florix machine for two years on various types of fruit, the results were very encouraging. Farmers such as Filiberto Montanari, who has used a Florix machine for several years, have reported a significant reduction in the time and labor required to thin flowers. ... >>

Advanced Infrared Microscope 02.05.2024

Microscopes play an important role in scientific research, allowing scientists to delve into structures and processes invisible to the eye. However, various microscopy methods have their limitations, and among them was the limitation of resolution when using the infrared range. But the latest achievements of Japanese researchers from the University of Tokyo open up new prospects for studying the microworld. Scientists from the University of Tokyo have unveiled a new microscope that will revolutionize the capabilities of infrared microscopy. This advanced instrument allows you to see the internal structures of living bacteria with amazing clarity on the nanometer scale. Typically, mid-infrared microscopes are limited by low resolution, but the latest development from Japanese researchers overcomes these limitations. According to scientists, the developed microscope allows creating images with a resolution of up to 120 nanometers, which is 30 times higher than the resolution of traditional microscopes. ... >>

Air trap for insects 01.05.2024

Agriculture is one of the key sectors of the economy, and pest control is an integral part of this process. A team of scientists from the Indian Council of Agricultural Research-Central Potato Research Institute (ICAR-CPRI), Shimla, has come up with an innovative solution to this problem - a wind-powered insect air trap. This device addresses the shortcomings of traditional pest control methods by providing real-time insect population data. The trap is powered entirely by wind energy, making it an environmentally friendly solution that requires no power. Its unique design allows monitoring of both harmful and beneficial insects, providing a complete overview of the population in any agricultural area. “By assessing target pests at the right time, we can take necessary measures to control both pests and diseases,” says Kapil ... >>

Random news from the Archive Tesla will release an amphibious electric car 10.04.2014 When Tesla set out to build an all-electric sports car that could compete with its gas-powered counterparts in this class, many doubted the venture would be successful. But Tesla claimed "Roadster", with acceleration to 60 miles per hour (96,6 km / h) in 3,7 seconds. The decision to create an electric sedan capable of competing with BMW and Mercedes cars was a success. The Model S is recognized by many as the best mass-produced car in the world. Tesla was able to poach many customers from well-known brands such as BMW, Mercedes, Audi and Toyota. Later, the Tesla Model X appeared - a luxury car with the power of a sports car and the functions of an SUV. Swing doors - the so-called. "wings of a falcon" - are the hallmark of this model. Also expected is a Model E electric vehicle with similar performance to the Model S, but at half the price. But Tesla is not going to stop there. The company plans to create an electric amphibious vehicle Model Y that can transform into a boat. Prior to that, there was only one mass-produced civilian amphibious vehicle - the German Amficar, which was produced from 1961 to 1964. The Tesla Model Y electric car will be useful for those regions in which there is a risk of flooding, increasing as climate change. Photos of Model Y are not yet available, but Elon Musk, CEO and chief product designer, said that the new electric car is similar to Model X. At the same time, Model Y will not have falcon wings, and doors that look like dolphin flippers will open accordingly.

Other interesting news:

▪ 6 handshakes or 19 clicks

▪ All living things shrink

▪ Vizio P Series Ultra HD Smart TVs

▪ Mercedes smart car watch

▪ Electronic jersey for a football player

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ site section Power supply. Article selection

▪ Article Garden paths. Tips for the home master

▪ article How are stars studied? Detailed answer

▪ article With a compass through magnetic fields. Children's Science Lab

▪ article General information on dyeing fabrics. Simple recipes and tips

▪ article Power regulator for electric heaters. Encyclopedia of radio electronics and electrical engineering

Leave your comment on this article:

All languages ​​of this page

Arabic	Hebrew	Polish
Bengali	Hindi	Portuguese
Chinese	Italian	Spanish
English	Japanese	Turkish
French	Korean	Ukrainian
German	Malay	Vietnamese

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

www.diagram.com.ua
2000-2024