Field effect transistor tester - measuring transistor parameters. Transistor test attachment

Before considering how to check the health of transistors, you need to know how to check the health of a p-n junction or how to properly test diodes. This is where we start ...

Semiconductor diode testing

When testing diodes using analogue ampere-volt meters, the lower measurement limits should be used. When checking a working diode, the resistance in the forward direction will be several hundred ohms, in the opposite direction - infinitely high resistance. In the event of a diode malfunction, a dial-up (analog) ammeter will show in both directions a resistance close to 0 (in case of diode breakdown) or infinitely high resistance in case of an open circuit. The resistance of junctions in the forward and reverse directions for germanium and silicon diodes is different.

Diode test with the help of digital multimeters it is carried out in the mode of their testing. In this case, if the diode is good, the display shows the voltage at the pn junction when measuring in the forward direction or a gap when measuring in the opposite direction. The value of the forward voltage at the junction for silicon diodes is 0.5 ... 0.8 V, for germanium - 0.2 ... 0.4 V. When checking a diode using digital multimeters in resistance measurement mode when checking a working diode, usually there is a gap in both the forward and reverse directions due to the fact that the voltage at the terminals of the multimeter is not enough for the junction to open.

For the most common bipolar transistors, testing them is similar to testing diodes., since the structure of the pnp or np-n transistor itself can be represented as two diodes (see the figure above), with the cathode or anode leads connected together, which are the output of the base of the transistor. When testing a transistor, the forward voltage at the junction of a healthy transistor will be 0.45 ... 0.9 V. In simpler words, when checking the base-emitter and base-collector junctions with an ohmmeter, a serviceable transistor in the forward direction has a low resistance and a high junction resistance in the opposite direction ... Additionally, you should check the resistance (voltage drop) between the collector and the emitter, which for a working transistor should be very large, except for the cases described below. However, there are some peculiarities when checking transistors. We will dwell on them in more detail.

One of the features is that some types of powerful transistors have a built-in snubber diode, which is connected between the collector and the emitter, and a resistor of about 50 ohms between the base and the emitter. This is primarily characteristic of horizontal output transistors. These additional elements disrupt the normal testing landscape. When checking such transistors, it is necessary to compare the parameters being checked with the same parameters of a knowingly serviceable transistor of the same type. When a digital multimeter checks transistors with a resistor in the base-emitter circuit, the voltage at the base-emitter junction will be close to or equal to 0 V.

Other "unusual" transistors are Darlington composite transistors. Outwardly, they look like ordinary ones, but in one case there are two transistors connected according to the scheme shown in Fig. 2. They are distinguished from ordinary ones by a high gain - more than 1000.

Testing of such transistors is no different, except that the forward voltage of the base-emitter junction is 1.2 ... 1.4 V. It should be noted that some types of digital multimeters in the testing mode have a voltage of less than 1.2 V at the terminals , which is not enough to open the pn junction, in which case the device shows a gap.

Testing unijunction and programmable unijunction transistors

A unijunction transistor (OPT) is distinguished by the presence of a section with negative resistance on its current-voltage characteristic. The presence of such a section indicates that such a semiconductor device can be used to generate oscillations (OPT, tunnel diodes, etc.).

The unijunction transistor is used in generator and switching circuits. To begin with, let's take a look at how a unijunction transistor differs from a programmable unijunction transistor. This is not difficult:

• common to them is a three-layer structure (like any transistor) with 2 pn junctions;
• a unijunction transistor has terminals called base 1 (B1), base 2 (B2), emitter. It becomes conductive when the voltage at the emitter exceeds the critical switching voltage, and remains in this state until the emitter current drops to a certain value, called the turn-off current. All this is very similar to the work of a thyristor;
• A programmable unijunction transistor has leads called an anode (A), a cathode (K), and a gate electrode (RE). According to the principle of operation, it is closer to a thyristor. Switching it occurs when the voltage at the control electrode exceeds the voltage at the anode (by about 0.6 V - the forward voltage of the pn junction). Thus, by changing the voltage at the anode with the help of the divider, it is possible to change the switching voltage of such a device, i.e. "program" it.

To check the serviceability of a single-junction and programmable single-junction transistor, measure the resistance between terminals B1 and B2 or A and K with an ohmmeter to check for breakdown. But the most accurate results can be obtained by assembling a circuit for testing single-junction and programmable single-junction transistors (see the diagram below - for OPT - fig. On the left, for programmable OPT - fig. On the right).

Checking digital transistors

Rice. 4 Simplified diagram of a digital transistor on the left, on the right is a test circuit. The arrow means "+" of the measuring device

Other unusual transistors are digital (internally bias transistors). Figure 4. above shows a diagram of such a digital transistor. The resistors R1 and R2 are the same and can be either 10 kΩ, 22 kΩ, or 47 kΩ, or mixed.

The digital transistor does not look different from the usual one, but the results of its "ringing" can baffle even an experienced craftsman. For many, they were both "incomprehensible" and remained so. In some articles, you can find the statement - "testing digital transistors is difficult ... The best option is to replace it with a known good transistor." This is undoubtedly the most reliable way to check. Let's try to figure out if this is really so. Let's figure out how to properly test a digital transistor and what conclusions to draw from the measurement results.

First, let's turn to the internal structure of the transistor, shown in Fig. 4, where the base-emitter and base-collector junctions are shown as two oppositely connected diodes for clarity. Resistors R1 and R2 can be either of the same rating, or they can differ and be either 10 kOhm, or 22 kOhm, or 47 kOhm, or have mixed ratings. Let the resistance of the resistor R1 be 10 kOhm, and R2 - 22 kOhm. The resistance of the open silicon junction is assumed to be 100 ohms. In particular, this value is shown by the Ts4315 dial gauge when measuring resistance at the x1 limit.

In the forward direction, the base-collector circuit of the transistor under consideration consists of a series-connected resistor R1 and the resistance of the base-collector junction proper (VD1 in Fig. 1). The junction resistance, since it is significantly less than the resistance of the resistor R1, can be neglected, and this measurement will give a value approximately equal to the value of the resistance of the resistor R1, which in our example is 10 kΩ. In the opposite direction, the junction remains closed, and no current flows through this resistor. The autometer hand should show "infinity".

The base-emitter circuit is a mixed connection of resistors R1, R2 and the resistance of the actual base-emitter junction (VD2 in Fig. 4 on the left). Resistor R2 is connected in parallel with this junction and practically does not change its resistance. Therefore, in the forward direction, when the junction is open, the ammeter will again show a resistance value approximately equal to the resistance value of the base resistor R1. When the polarity of the tester is reversed, the base-emitter junction remains closed and current flows through the series-connected resistors R1 and R2. In this case, the tester will show the sum of these resistances. In our example, it will be approximately 32 kΩ.

As you can see, in the forward direction, the digital transistor is tested in the same way as a conventional bipolar transistor, with the only difference that the arrow of the device shows the value of the resistance of the base resistor. And by the difference between the measured resistances in the forward and reverse directions, you can determine the value of the resistance of the resistor R2.

Now let's look at testing the emitter-collector circuit. This circuit consists of two oppositely connected diodes, and for any polarity of the tester, its arrow should show "infinity". However, this statement is only true for a conventional silicon transistor.

In this case, due to the fact that the base-emitter junction (VD2) is shunted by the resistor R2, it becomes possible to open the base-collector junction with the corresponding polarity of the measuring device. The resistance of the transistors measured in this case has some scatter, but for a preliminary estimate, you can focus on a value about 10 times less than the resistance of the resistor R1. When changing the polarity of the tester, the resistance of the base-collector junction must be infinitely large.

In fig. 4 on the right summarizes the above, which is convenient to use in everyday practice. For a forward transistor, the arrow will represent the “-” of the meter.

As a measuring device, it is necessary to use dial (analog) AVO meters with a head deflection current of about 50 μA (20 kOhm / V).

It should be noted that the above is somewhat idealized, and in practice, there may be situations requiring a logical understanding of the measurement results. Especially in cases where the digital transistor turns out to be defective.

How to check a MOSFET transistor

There are several different ways to test MOSFETs. For example like this:

• Check the resistance between gate-source (3-I) and gate-drain (3-C). It must be infinitely large.
• Connect the gate to the source. In this case, the source-drain (I-S) transition should be called like a diode (an exception for MOS transistors that have built-in breakdown protection - a zener diode with a certain opening voltage).

The most common and typical malfunction of MOSFETs is a short circuit between the gate-source and gate-drain.

Another way is to use two ohmmeters. The first one is switched on to measure between the source and drain, the second - between the source and the gate. The second ohmmeter must have a high input resistance - about 20 MΩ and the voltage at the terminals is at least 5 V. When the second ohmmeter is connected in direct polarity, the transistor will open (the first ohmmeter will show a resistance close to zero), when the polarity changes to the opposite, the transistor will close. The disadvantage of this method is the requirements for the voltage at the terminals - the second ohmmeter. Naturally, digital multimeters are not suitable for these purposes. This limits the use of this verification method.

Another way is similar to the second one. First, the terminals of the gate and the source are briefly connected together in order to remove the charge present on the gate. Next, an ohmmeter is connected to the source-drain terminals. They take a 9 V battery and briefly connect it with a plus to the gate, and a minus to the source. The transistor will open and will remain open for some time after the battery is disconnected due to the conservation of charge. Most MOSFETs turn on at a gate-source voltage of about 2 V.

When testing MOSFETs, be very careful not to damage the transistor by static electricity.

How to determine the structure and location of the terminals of transistors, the type of which is unknown

When determining the structure of a transistor, the type of which is unknown, one should go through six options - determine the base output, and then measure the forward voltage at the junctions. The forward voltage at the base-emitter junction is always several millivolts higher than the forward voltage at the base-collector junction (when using an arrow multimeter, the base-emitter junction resistance in the forward direction is slightly higher than the base-collector junction resistance). This is due to the technology of manufacturing transistors, and the rule applies to ordinary bipolar transistors, with the exception of some types of power transistors that have a built-in damper diode. The polarity of the probe of the multimeter connected during measurements at the transitions in the forward direction to the base of the transistor will indicate the type of transistor: if it is "+" - the transistor of the n-p-n structure, if "-" - the p-n-p structure.

Simple heterodyne resonance indicator.

With a short-circuited L2 coil, the GIR allows you to determine the resonant frequency from 6 MHz

up to 30 MHz. With the L2 coil connected, the frequency measurement range is from 2.5 MHz to 10 MHz.

The resonant frequency is determined by rotating the C1 rotor and observing on the oscilloscope screen

signal change.

High frequency signal generator.

The high frequency signal generator is designed for testing and adjusting various high frequency devices. The range of generated frequencies 2 ..80 MHz is divided into five sub-bands:

I - 2-5 MHz

II - 5-15 MHz

III - 15 - 30 MHz

IV - 30 - 45 MHz

V - 45 - 80 MHz

The maximum amplitude of the output signal at a load of 100 Ohm is about 0.6 V. The generator provides a smooth adjustment of the amplitude of the output signal, as well as the ability to

amplitude and frequency modulation of the output signal from an external source. The generator is powered from an external DC voltage source of 9 ... 10 V.

The schematic diagram of the generator is shown in the figure. It consists of an RF master oscillator made on the V3 transistor and an output amplifier on the V4 transistor. The generator is made according to the inductive three-point scheme. The required sub-range is selected with the switch S1, and the generator is rebuilt with a variable capacitor C7. From the drain of the transistor V3, the RF voltage is supplied to the first gate

field-effect transistor V4. In FM mode, low-frequency voltage is applied to the second gate of this transistor.

Frequency modulation is carried out using a VI varicap, to which the LF voltage is applied in FM mode. At the generator output, the HF voltage is smoothly regulated by the resistor R7.

The generator is assembled in a case made of one-sided foil fiberglass with a thickness of 1.5 mm, dimensions 130X90X48 mm. The front panel of the generator is equipped with

switches S1 and S2 of P2K type, resistor R7 of PTPZ-12 type, variable capacitor C7 of KPE-2V type from the Alpinist-405 radio receiver, in which both sections are used.

Coil L1 is wound on a ferrite magnetic core M1000NM (K10X6X X4, b) and contains (7 + 20) turns of wire PELSHO 0.35. Coils L2 and L3 are wound on bobbins with a diameter of 8 and a length of 25 mm with carbonyl tuned cores of a diameter of 6 and a length of 10 mm. The L2 coil consists of 5 + 15 turns of PELSHO 0.35 wire, L3 - of 3 + 8 turns. L4 and L5 coils frameless

with a diameter of 9 mm are wound with wire PEV-2, 1.0. Coil L4 contains 2 + 4 turns, and L5 has 1 + 3 turns.

The establishment of the generator begins with checking the installation. Then the supply voltage is applied and, using an HF voltmeter, the presence of generation on all sub-bands is checked. Borders

ranges are specified using a frequency meter, and, if necessary, capacitors C1-C4 (C6) are selected, adjusted with the cores of the coils L2, L3 and the distance between the turns of the coils L4 and L5 is changed.

Multimeter-HF millivoltmeter.

Now the most affordable and most common radio amateur's device has become a digital multimeter of the M83x series.

The device is intended for general measurements and therefore does not have specialized functions. Meanwhile, if you are into radio receiving or transmitting equipment, you need to measure

small RF voltages (local oscillator, amplifier stage output, etc.), adjust the circuit. To do this, the multimeter must be supplemented with a simple remote measuring head containing

high-frequency detector based on germanium diodes. The input capacitance of the RF head is less than 3 pF, which allows it to be connected directly to the local oscillator or stage. You can use diodes D9, GD507 or D18, diodes D18 gave the highest sensitivity (12 mV). The RF head is assembled in a shielded case, on which there are terminals for connecting the probe or conductors to the measured circuit. Communication with a multimeter using a shielded TV cable RK-75.

Measuring small capacitances with a multimeter

Many radio amateurs use multimeters in their laboratories; some of them also allow measuring the capacitance of capacitors. But as practice shows, these devices cannot measure the capacitance up to 50 pF, and up to 100 pF - a large error. In order to be able to measure small capacities, this attachment is intended. Having connected the attachment to the multimeter, you need to set the value of 100pf on the indicator, adjusting C2. Now, when a 5 pF capacitor is connected, the device will show 105. It remains only to subtract the figure 100

Hidden wiring finder

A relatively simple finder made on three transistors (Fig. 1) will help to determine the place of hidden electrical wiring in the walls of the room. A multivibrator is assembled on two bipolar transistors (VT1, VT3), and an electronic key on the field (VT2).

The principle of operation of the seeker is based on the fact that an electric field is formed around an electric wire and the seeker catches it. If the SB1 switch button is pressed, but there is no electric field in the area of ​​the WA1 antenna probe, or the finder is far from the mains wires, the VT2 transistor is open, the multivibrator does not work, the HL1 LED is off. It is enough to bring the antenna probe connected to the gate circuit of the field

transistor, to a conductor with a current or just to a network cable, the transistor VT2 will close, the shunting of the base circuit of the transistor VT3 will stop and the multivibrator will take effect. The LED will start flashing. By moving the antenna probe close to the wall, it is easy to trace the network wires through it.

The device also allows you to find the location of the phase wire break. To do this, you need to plug in a load, for example a table lamp, and move the antenna probe of the device along the wiring. In the place where the LED stops flashing, you need to look for a malfunction.

The field-effect transistor can be any other of the series indicated on the diagram, and the bipolar transistor can be any of the KT312, KT315 series. Everything

resistors - MLT-0.125, oxide capacitors - K50-16 or other small-sized ones, LED - any of the AL307 series, power supply battery "Krona" or rechargeable battery with a voltage of 6 ... 9 V, push-button switch SB1 - KM-1 or similar. Some parts of the device are mounted on a board (Fig. 2) made of one-sided foil-clad fiberglass. A plastic case can become the body of the finder (Fig. 3)

for storing school counting sticks. A board is attached in its upper compartment, and a battery is located in the lower compartment. A switch and an LED are attached to the side wall of the upper compartment, and an antenna probe is attached to the upper wall. It is a conical

a plastic cap with a threaded metal rod inside. The rod is attached to the body with nuts, from the inside of the body, a metal tab is put on the rod, which is connected with a flexible conductor to the resistor R1 on the board. The antenna probe can be of a different design, for example, in the form of a loop made from a piece of thick (5 mm) high-voltage wire used in a TV. Length

a segment of 80 ... 100 mm, its ends are passed through the holes in the upper compartment of the case and soldered to the corresponding point of the board. The desired oscillation frequency of the multivibrator, which means that the frequency of the LED flashes can be set by selecting the resistors RЗ, R5 or capacitors C1, C2. To do this, temporarily disconnect the source output from the resistors RЗ and R4.

left transistor and close the switch contacts. If, when searching for a break in the phase wire, the sensitivity of the device turns out to be excessive, it is easy to reduce it by reducing the length of the antenna probe or disconnecting the conductor connecting the probe to the printed circuit board. The finder can be assembled according to a slightly different scheme (Fig. 4) using bipolar transistors of different structures - a generator is made on them. The field-effect transistor (VT2) still controls the operation of the generator when the antenna probe WA1 hits the electric field of the network wire.

Transistor VT1 can be series

KT209 (with indexes A-E) or KT361,

VT2 - any of the KP103 series, VT3 - any of the KT315, KT503, KT3102 series. Resistor R1 can be 150 ... 560 Ohm, R2 - 50 kOhm ... 1.2 MΩ, R3 and R4 with a deviation from the ratings indicated in the diagram by ± 15%, capacitor C1 - with a capacity of 5 ... 20 μF. The printed circuit board for this version of the finder is smaller (Fig. 5), but the design is practically the same as in the previous version.

Any of the described searchers can be used to control the operation of the ignition system of cars. Bringing the antenna probe of the finder to the high-voltage wires, by the blinking of the LED, they determine the circuits that do not receive high voltage, or look for a faulty spark plug.

Radio magazine, 1991, №8, p.76

Not quite the usual GIR scheme is shown in the figure. The difference is in the external communication loop. Loop L1 is made of copper wire with a diameter of 1.8 mm, the loop diameter is about 18 mm, the length of its leads is 50 mm. The hinge is inserted into the slots located at the end of the case. L2 is wound on a standard ribbed case and contains 37 turns of 0.6 mm wire with taps from 15, 23, 29 and 32 turns Range - 5.5 to 60 MHz

Simple capacitance meter

The capacitance meter allows you to measure the capacitance of capacitors from 0.5 to 10000pF.

A multivibrator is assembled on TTL D1.1 D1.2 logic gates, the frequency of which depends on the resistance of the resistor connected between the D1.1 input and the D1.2 output. For each measurement limit, a certain frequency is set using S1, one section of which switches the resistors R1-R4, and the other capacitors C1-C4.

The pulses from the output of the multivibrator are fed to the power amplifier D1.3 D1.4 and then through the reactance of the measured capacitor Cx to a simple AC voltmeter on the P1 microammeter.

The readings of the device depend on the ratio of the active resistance of the device frame and R6, and the reactance Cx. In this case, Cx depends on the capacitance (the more, the less the resistance).

The device is calibrated at each limit using trimming resistors R1-R4 by measuring capacitors with known capacitances. The sensitivity of the indicator of the device can be set by selecting the resistance of the resistor R6.

Literature RK2000-05

Simple Function Generator

In an amateur radio laboratory, a functional generator must be a mandatory attribute. We present to your attention a function generator capable of generating sinusoidal, rectangular, triangular signals with high stability and accuracy. If desired, the output signal can be modulated.

The frequency range is divided into four sub-bands:

1.1Hz-100Hz,

2.100Hz-20kHz,

3.20 kHz-1 MHz,

4.150KHz-2 MHz.

The exact frequency can be set using potentiometers P2 (coarse) and P3 (fine)

function generator regulators and switches:

P2 - coarse frequency setting

P3 - Fine Tuning Frequency

P1 - Signal amplitude (0 - 3V with 9V supply)

SW1 - range switch

SW2 - Sine / triangle signal

SW3 - Sinusoidal (triangular) / square wave

To monitor the generator frequency, the signal can be taken directly from pin 11.

Options:

Sinusoidal signal:

Distortion: less than 1% (1 kHz)

Flatness: +0.05 dB 1 Hz - 100 kHz

Square wave:

Amplitude: 8V (no load) with 9V supply

Rise Time: Less than 50 ns (at 1 kHz)

Fall time: less than 30ns (at 1kHz)

Unbalance: less than 5% (1 kHz)

Triangle signal:

Amplitude: 0 - 3V with 9V supply

Linearity: less than 1% (up to 100 kHz)

Overvoltage protection

The ratio of capacitances C1 and composite C2 and C3 affects the output voltage. Rectifier power is enough for parallel switching of 2-3x relays of RP21 type (24v)

174x11 generator

The figure shows a generator on a K174XA11 microcircuit, the frequency of which is controlled by voltage. When the capacitance C1 changes from 560 to 4700pF, a wide frequency range can be obtained, while the frequency is adjusted by changing the resistance R4. For example, the author found out that, with C1 = 560pF, the frequency of the generator can be changed with R4 from 600Hz to 200kHz, and with C1 4700pF from 200Hz to 60kHz.

The output signal is taken from pin 3 of the microcircuit with an output voltage of 12V, the author recommends that the signal from the microcircuit output be fed through a current-limiting resistor with a resistance of 300 Ohm.

Inductance meter

The proposed device allows you to measure the inductance of the coils on three measurement ranges - 30, 300 and 3000 μH with an accuracy of at least 2% of the scale value. The readings are not affected by the coil's own capacitance and its ohmic resistance.

On the elements 2I-NOT of the DDI microcircuit, a generator of rectangular pulses is assembled, the repetition rate of which is determined by the capacitance of the capacitor C1, C2 or C3, depending on the included measurement limit by the switch SA1. These pulses are fed through one of the capacitors C4, C5 or C6 and the diode VD2 to the measured coil Lx, which is connected to terminals XS1 and XS2.

After the termination of the next pulse during a pause due to the accumulated energy of the magnetic field, the current through the coil continues to flow in the same direction through the VD3 diode, its measurement is carried out by a separate current amplifier collected on transistors T1, T2 and a pointer device PA1. Capacitor C7 smoothes the ripple current. The VD1 diode is used to reference the level of the pulses arriving at the coil.

When setting up the device, it is necessary to use three reference coils with inductances of 30, 300 and 3000 μH, which are alternately connected instead of L1, and the arrow of the device is set to the maximum scale division with the corresponding variable resistor R1, R2 or R3. During the operation of the meter, it is enough to calibrate the variable resistor R4 at the measurement limit of 300 μH, using the L1 coil and turning on the SB1 switch. The microcircuit is powered from any source with a voltage of 4.5 - 5 V.

The current consumption of each battery is 6 mA. The current amplifier for the milliammeter can not be assembled, but parallel to the capacitor C7, connect a microammeter with a scale of 50 μA and an internal resistance of 2000 Ohm. Inductance L1 can be composite, but then the individual coils should be placed mutually perpendicular or as far apart as possible. For ease of installation, all connecting wires are equipped with plugs, and the corresponding sockets are installed on the boards.

Simple indicator of radioactivity

Heterodyne Resonance Indicator

  G. Gvozditsky

The schematic diagram of the proposed GIR is shown in Fig. 1. Its local oscillator is made on a field-effect transistor VT1, connected in a common-source circuit. Resistor R5 limits the drain current of the FET. Choke L2 is an element of decoupling the local oscillator from the power supply at high frequency.

Diode VD1, connected to the gate and source pins of the transistor, improves the generated voltage shape, bringing it closer to sinusoidal. Without a diode, the positive half-wave of the drain current will become distorted due to an increase in the gain of the transistor with an increase in the gate voltage, which inevitably leads to the appearance of even harmonics in the spectrum of the local oscillator signal

Through the capacitor C5, the radio frequency voltage is fed to the input of a high-frequency voltmeter-indicator, consisting of a detector, the diodes VD2 and VD4 of which are connected according to a voltage doubling circuit, which increases the sensitivity of the detector and the stability of the DC amplifier on a transistor VT2 with a RA1 microammeter in a collector target. The VD3 diode stabilizes the exemplary voltage across the VD2, VD4 diodes. Using a variable resistor R3 combined with a power switch SA1, set the arrow of the PA1 microammeter to its original position at the extreme right scale mark

If in some parts of the range it is necessary to increase the accuracy of the scale, then connect a mica capacitor of constant capacity in parallel with the coil.

A variant of the coils made on frames from laboratory blood collection tubes are shown in the photo (Fig. 2) and are selected by a radio amateur for the desired range

The inductance of the loop coil and the capacitance of the loop, taking into account the additional capacitor, can be calculated using the formula

LC = 25330 / f²

where C is in picofarads, L is in microhenry, f is in megahertz.

Determining the resonant frequency of the circuit under study, the GIR coil is brought to it as close as possible and slowly rotating the handle of the KPI unit, the indicator readings are monitored. As soon as its arrow swings to the left, mark the corresponding position of the KPE handle. With further rotation of the tuning knob, the arrow of the device returns to its original position. The mark on the scale where the maximum * dip * of the arrow is observed will exactly correspond to the resonant frequency of the circuit under study

In the described GIR there is no additional stabilizer of the supply voltage, therefore, when working with it, it is recommended to use a source with the same DC voltage value - optimally, a network power supply with a stabilized output voltage.

It is impractical to make one common scale for all ranges due to the complexity of such work. Moreover, the accuracy of the obtained scale at different density of the adjustment of the applied contours will complicate the use of the device.

L1 coils are impregnated with epoxy glue or HH88. It is advisable to wind them on the HF ranges with a copper silver-plated wire with a diameter of 1.0 mm.

Structurally, each contour coil is located on the basis of the common SG-3 connector. It is glued into the coil frame.

Simplified version of the GIR

It differs from G. Gvozditskiy's GIR in what was already written about in the article - the presence of an average output of the replaceable coil L1, a Tesla variable capacitor with a solid dielectric is used, there is no diode that forms a sinusoidal signal. There is no rectifier-doubler of HF voltage and DCT, which reduces the sensitivity of the device.

On the positive side, it should be noted the presence of "stretching" disconnectable capacitors C1, C2 and the simplest vernier, combined with two switching scales that can be graduated with a pencil, the power is turned on by the button only at the time of measurements, which saves the battery.

To power the Geiger counter B1, a voltage of 400V is required, this voltage is generated by a source on a blocking generator on a transistor VT1. Pulses from the step-up winding T1 are rectified by a rectifier at VD3C2. The voltage at C2 goes to B1, the load of which is the resistor R3. When an ionizing particle passes through B1, a short current pulse arises in it. This pulse is amplified by a pulse shaping amplifier at VT2VT3. As a result, a longer and stronger current pulse flows through F1-VD1 - the LED flashes, and a click is heard in the F1 capsule.

The Geiger counter can be replaced with any similar one, F1 any electromagnetic or dynamic resistance of 50 Ohm.

T1 is wound on a ferrite ring with an outer diameter of 20 mm, the primary winding contains 6 + 6 turns of wire PEV 0.2, the secondary one is 2500 turns of wire PEV 0.06. An insulating material made of varnished cloth must be laid between the windings. The secondary winding is wound first, the surface on it, evenly, is secondary.

Capacitance meter

The device has six subranges, the upper limits for which are 10pf, 100pf, 1000pf, 0.01mkf, 0.1mkf and 1mkf, respectively. The capacity is read on a linear microammeter scale.

The principle of operation of the device is based on measuring the alternating current flowing through the investigated capacitor. On the operational amplifier DA1, a rectangular pulse generator is assembled. The repetition rate of these pulses depends on the capacity of one of the capacitors C1-C6 and the position of the trimmer slider R5. Depending on the sub-band, it varies from 100Hz to 200kHz. With a trimmer R1, we set a symmetrical waveform (meander) at the output of the generator.

Diodes D3-D6, trimming resistors R7-R11 and microammeter PA1 form an AC meter. In order for the measurement error to not exceed 10% in the first sub-range (capacity up to 10pF), the internal resistance of the microammeter should be no more than 3 kOhm. On the other sub-ranges, trimming resistors R7-R11 are connected in parallel to PA1.

The required measurement sub-range is set with the SA1 switch. With one group of contacts, it switches the frequency-setting capacitors C1-C6 in the generator, with the other - the trimming resistors in the indicator. To power the device, a stabilized bipolar source for a voltage of 8 to 15V is required. The ratings of the frequency-setting capacitors C1-C6 may differ by 20%, but the capacitors themselves must have a sufficiently high temperature and time stability.

The device is adjusted in the following sequence. First, on the first sub-band, symmetrical oscillations are achieved with the resistor R1. In this case, the motor of the resistor R5 should be in the middle position. Then, connecting a 10pf reference capacitor to the "Cx" terminals, set the microammeter arrow to the division corresponding to the capacity of the reference capacitor with a trimming resistor R5 (when using a 100μA device, by the final scale division).

Prefix diagram

Attachment to a frequency meter for determining the frequency of the loop tuning and its presetting. The attachment is operational in the range of 400 kHz-30 MHz.T1 and T2 can be KP307, BF 245

LY2BOK

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Transistor test attachment

V. Kalendo. An attachment for testing transistors. The idea of ​​using diode bridges in measuring technology, known from publications in the journal, allowed the author of the article to develop a simple attachment - a kind of switching unit for controlling the parameters of bipolar and field-effect transistors of almost all types. The attachment allows you to measure the static current transfer coefficient of bipolar transistors at fixed values ​​of the base current (10, 30, 100, 300 μA; 1, 3, 10, 30 mA), the initial drain current of field-effect transistors with p-n junction or built-in channel; drain current of field-effect transistors with an induced channel at a gate voltage equal to half the drain-source voltage; the slope of the characteristics of field-effect transistors with two gates for each of them; the slope of the characteristics of field-effect transistors when using the output of the substrate (body-substrate) as the second gate. The device is made on a KP302BM transistor and 10 diodes (4 x KD522A and 6 x KD212A).

But, among the radio components, there are those that are difficult to check with an ordinary multimeter, and sometimes impossible. These include field-effect transistors (like MOSFET and J-FET). Also, an ordinary multimeter does not always have the function of measuring the capacity of capacitors, including electrolytic ones. And even if there is such a function, then the device, as a rule, does not measure another very important parameter of electrolytic capacitors - equivalent series resistance (EPS or ESR).

Recently, universal meters R, C, L and ESR have become affordable. Many of them have the ability to check almost all common radio components.

Let's find out what capabilities such a tester has. In the photo, the universal tester R, C, L and ESR - MTester V2.07(QS2015-T4). Aka LCR T4 Tester. I got it on Aliexpress. Do not be surprised that the device is without a case, it costs much more with it. option without a body, but with a body.

The tester of radio components is assembled on the Atmega328p microcontroller. Also on the PCB there are SMD transistors marked J6(bipolar S9014), M6(S9015), integrated stabilizer 78L05, TL431 - precision voltage regulator (adjustable zener diode), SMD diodes 1N4148, quartz at 8.042 MHz. and "loose" - planar capacitors and resistors.

The device is powered by a 9V battery (size 6F22). However, if one is not at hand, the device can be powered from stabilized power supply.

A ZIF-panel is installed on the printed circuit board of the tester. The numbers 1,2,3,1,1,1,1 are indicated next to it. The additional terminals on the top row of the ZIF panel (those 1,1,1,1) duplicate terminal number 1. This is to make it easier to install exploded parts. By the way, it is worth noting that the bottom row of terminals duplicates terminals 2 and 3. For 2 there are 3 additional terminals, and for 3 already 4. This can be seen by examining the layout of the printed conductors on the other side of the printed circuit board.

So what are the capabilities of this tester?

Measurement of capacity and parameters of an electrolytic capacitor.

I also advise you to look at the page that tells about the types of field-effect transistors and their designation in the diagram... This will help you understand what the device is showing you.

Checking bipolar transistors.

Let's take our KT817G as a guinea pig. As you can see, the gain is measured for bipolar transistors hFE(he is h21e) and bias voltage BE (opening the transistor) Uf... For silicon bipolar transistors, the bias voltage is between 0.6 ~ 0.7 volts. For our KT817G, it was 0.615 volts (615mV).

Composite Bipolar Transistors recognizes too. Here are just the parameters on the display, I would not believe. Well, really. A composite transistor cannot have a gain hFE = 37. For KT973A, the minimum hFE must be at least 750.

As it turned out, the structure for KT973A (PNP) and KT972A (NPN) determines correctly. But everything else measures incorrectly.

It is worth considering that if at least one of the transitions of the transistor is broken, then the tester can define it as a diode.

Checking diodes with a universal tester.

The test piece is a 1N4007 diode.

For diodes, the voltage drop at the p-n junction in the open state is indicated Uf... In the technical documentation for diodes, it is indicated as V F- Forward Voltage (sometimes V FM). Note that with different forward currents through the diode, the value of this parameter also changes.

For a given diode 1N4007: V F= 677mV (0.677V). This is the normal value for a low frequency rectifier diode. But at Schottky diodes this value is lower, therefore they are recommended for use in devices with low-voltage autonomous power supply.

In addition, the tester also measures the capacity of the p-n junction. (C= 8pF).

The result of checking the KD106A diode. As you can see, the capacitance of the junction is many times greater than that of the 1N4007 diode. As many as 184 picofarads!

If, instead of a diode, you install an LED and turn on the test, then during testing it will blink cheerfully.

For LEDs, the tester shows the capacitance of the junction and the minimum voltage at which the LED opens and begins to emit. Specifically for this red LED, it was Uf = 1.84V.

As it turned out, the universal tester also copes with checking dual diodes, which can be found in computer power supplies, voltage converters of car amplifiers, and all kinds of power supplies.

Dual diode test MBR20100CT.

The tester shows the voltage drop across each of the diodes Uf = 299mV (in datasheets it is indicated as V F), as well as a pinout. Do not forget that dual diodes are available with both a common anode and a common cathode.

Checking resistors.

This tester does an excellent job of measuring the resistance of resistors, including variables and trimmers. This is how the device detects a 1 kΩ type 3296 trimmer. On the display, the variable or trimmer resistor is shown as two resistors, which is not surprising.

You can also check fixed resistors with resistances down to a fraction of an ohm. Here's an example. 0.1 Ohm resistor (R10).

Measurement of inductance of coils and chokes.

In practice, the function of measuring the inductance at coils and chokes... And if large-sized products are labeled with parameters, then there is no such marking on small-sized and SMD inductors. The device will help in this case too.

The display shows the result of the measurement of the parameters of the throttle at 330 μH (0.33 milliHenry).

In addition to the inductance of the choke (0.3 mH), the tester determined its DC resistance - 1 ohm (1.0Ω).

This tester checks low-power triacs without problems. For example, I checked them MCR22-8.

And here is a more powerful thyristor BT151-800R in the TO-220 case, the device could not be tested and displayed an inscription "? No, unknown or damaged part" , which loosely means "Missing, unknown or damaged part".

Among other things, the universal tester can measure the voltage of batteries and accumulators.

I was also delighted that this device can be used to check optocouplers. True, such "component" parts can be checked only in several stages, since they consist of at least two parts isolated from each other.

Let me show you with an example. Here is the internals of the TLP627 optocoupler.

The emitting diode is connected to pins 1 and 2. Let's connect them to the terminals of the device and see what it shows us.

As you can see, the tester determined that a diode was connected to its terminals and displayed the voltage at which it begins to emit Uf = 1.15V. Next, we connect the optocoupler leads to the tester 3 and 4.

This time, the tester determined that a regular diode was connected to it. There is nothing surprising. Take a look at the internal structure of the TLP627 optocoupler and you will see that a diode is connected to the emitter and collector pins of the phototransistor. He shunts the terminals of the transistor and the tester "sees" only him.

So we checked the operability of the TLP627 optocoupler. In a similar way, I was able to check the low-power solid state relay type К293КП17Р.

Now I’ll tell you what details this tester does NOT check.

Powerful thyristors. When checking the BT151-800R thyristor, the device showed on the display a bipolar transistor with zero hFE and Uf values. Another instance of the thyristor was identified as faulty. Perhaps this is indeed the case;

Zener Diodes... Defines as a diode. You will not get the basic parameters of the zener diode, but you can make sure that the P-N junction is intact. The manufacturer declared the correct recognition of zener diodes with a stabilization voltage of less than 4.5V.
When repairing, I still recommend not to rely on the readings of the device, but to replace the zener diode with a new one, since it happens that the zener diodes are in good order, but the stabilization voltage is "walking";

Any microcircuits such as integrated stabilizers 78L05, 79L05 and the like. I think the explanations are superfluous;

Dinistors... Actually, this is understandable, since the dinistor opens only at a voltage of several tens of volts, for example, 32V, as in the common DB3;

Supercapacitors the device does not recognize either. Apparently due to the long charge time;

Varistors defines as capacitors;

Unidirectional suppressors defines as diodes.

A universal tester will not be left idle for any radio amateur, and radio mechanics will save a lot of time and money.

It should be understood that when checking faulty semiconductor elements, the device may determine the type of element incorrectly. So, a bipolar transistor with one punctured pn junction, it can be defined as a diode. And a swollen electrolytic capacitor with a huge leak is recognized as two counter-connected diodes. This has happened. I think there is no need to explain that this indicates the inadequacy of the radio component.

But, it is worth considering the fact that there is also an incorrect determination of values ​​due to poor contact of the pins of the part in the ZIF-panel. Therefore, in some cases, the part must be reinstalled in the panel and checked.