The reason for the creation of this device was a considerable number of accumulated quartz resonators, both purchased and soldered from different boards, and many lacked any markings. Traveling through the vast expanses of the Internet and trying to assemble and launch various ones, it was decided to come up with something of our own. After many experiments with different generators, both on different digital logics and on transistors, I chose the 74HC4060, although it was also not possible to eliminate self-oscillations, but as it turned out, this does not create interference during the operation of the device.

Quartz meter circuit

The device is based on two CD74HC4060 generators (74HC4060 was not in the store, but judging by the datasheet they are even “cooler”), one operates at a low frequency, the second at a high one. The lowest-frequency ones I had were hour quartz, and the highest frequency was non-harmonic quartz at 30 MHz. Due to their tendency to self-excite, it was decided to switch the generators simply by switching the supply voltage, which is indicated by the corresponding LEDs. After the generators, I installed a logic repeater. It might be better to install capacitors instead of resistors R6 and R7 (I haven’t checked it myself).

As it turned out, the device runs not only quartz, but also all sorts of filters with two or more legs, which were successfully connected to the appropriate connectors. One “biped” similar to a ceramic capacitor was launched at 4 MHz, which was later successfully used instead of a quartz resonator.

The photographs show that two types of connectors are used to test radio components. The first is made from parts of panels - for lead-out parts, and the second is a fragment of the board glued and soldered to the tracks through the corresponding holes - for SMD quartz resonators. To display information, a simplified frequency meter is used on the PIC16F628 or PIC16F628A microcontroller, which automatically switches the measurement limit, that is, the frequency on the indicator will be either kHz or in MHz.

About device details

Part of the board is assembled on lead parts, and part on SMD. The board is designed for the Winstar single-line LCD indicator WH1601A (this is the one with the contacts at the top left), contacts 15 and 16, which serve for illumination, are not routed, but anyone who needs can add tracks and details for themselves. I didn’t turn on the backlight because I used a non-backlit indicator from some phone on the same controller, but at first there was a Winstar one. In addition to WH1601A, you can use WH1602B - two-line, but the second line will not be used. Instead of a transistor in the circuit, you can use any of the same conductivity, preferably with a larger h21. The board has two power inputs, one from a mini USB, the other through a bridge and 7805. There is also space for a stabilizer in another case.

Device setup

When tuning with the S1 button, turn on the low-frequency mode (the VD1 LED will light up) and by inserting a quartz resonator at 32768 Hz into the corresponding connector (preferably from the computer motherboard), use the tuning capacitor C11 to set the frequency on the indicator to 32768 Hz. Resistor R8 sets the maximum sensitivity. All files - boards, firmware, datasheets for the radio elements used and more, download in the archive. Author of the project - nefedot.

Discuss the article DEVICE FOR CHECKING QUARTZ FREQUENCY

A quartz resonator is an electronic device based on the piezoelectric effect, as well as mechanical resonance. It is used by radio stations, where it sets the carrier frequency in clocks and timers, fixing an interval of 1 second in them.

What is it and why is it needed

The device is a source that provides high-precision harmonic oscillations. Compared with analogues, it has greater operating efficiency and stable parameters.

First samples modern devices appeared on radio stations in 1920-1930. as elements that have stable operation and are capable of setting the carrier frequency. They:

• replaced crystal resonators operating on Rochelle salt, which appeared in 1917 as a result of the invention of Alexander M. Nicholson and were characterized by instability;
• replaced the previously used circuit with a coil and a capacitor, which did not have a high quality factor (up to 300) and depended on temperature changes.

A little later, quartz resonators became an integral part of timers and clocks. Electronic components with a natural resonant frequency of 32768 Hz, which in a binary 15-bit counter sets a time period equal to 1 second.

The devices are used today in:

• quartz watch, ensuring their accuracy of operation regardless of the ambient temperature;
• measuring instruments, guaranteeing them high accuracy of indicators;
• marine echo sounders, which are used in research and creation of bottom maps, recording reefs, shoals, and searching for objects in the water;
• circuits corresponding to reference oscillators that synthesize frequencies;
• circuits used in wave indication of SSB or telegraph signal;
• radio stations with DSB signal with intermediate frequency;
• bandpass filters of superheterodyne receivers, which are more stable and high quality than LC filters.

The devices are manufactured with different housings. They are divided into output ones, used in volumetric mounting, and SMD, used in surface mounting.

Their operation depends on the reliability of the switching circuit, which affects:

• frequency deviation from the required value, parameter stability;
• rate of aging of the device;
• load capacity.

Properties of a quartz resonator

Superior to previously existing analogues, which makes the device indispensable in many electronic circuits and explains the scope of use of the device. This is confirmed by the fact that in the first decade since its invention, more than 100 thousand devices were produced in the USA (not counting other countries).

Among the positive properties of quartz resonators that explain the popularity and demand for devices:

• good quality factor, the values ​​of which – 104-106 – exceed the parameters of previously used analogues (they have a quality factor of 300);
• small dimensions, which can be measured in fractions of a millimeter;
• resistance to temperature and its fluctuations;
• long service life;
• ease of manufacture;
• the ability to build high-quality cascade filters without using manual settings.

Quartz resonators also have disadvantages:

• external elements allow you to adjust the frequency in a narrow range;
• have a fragile design;
• cannot tolerate excessive heat.

Operating principle of a quartz resonator

The device operates on the basis of the piezoelectric effect, which manifests itself on a low-temperature quartz plate. The element is cut out from a solid quartz crystal, observing the specified angle. The latter determines the electrochemical parameters of the resonator.

The plates are coated on both sides with a layer of silver (platinum, nickel, gold are suitable). They are then firmly fixed in the housing, which is sealed. The device is an oscillatory system that has its own resonant frequency.

When the electrodes are subjected to alternating voltage, the quartz plate, which has piezoelectric properties, bends, contracts, and shifts (depending on the type of crystal processing). At the same time, a back-EMF appears in it, as happens in an inductor located in an oscillatory circuit.

When a voltage is applied with a frequency that matches the natural vibrations of the plate, resonance is observed in the device. Simultaneously:

• the quartz element increases the amplitude of vibrations;
• The resonator resistance is greatly reduced.

The energy required to maintain oscillations is low in the case of equal frequencies.

Designation of a quartz resonator on an electrical diagram

The device is designated similarly to a capacitor. Difference: a rectangle is placed between the vertical segments - a symbol of a plate made of a quartz crystal. A gap separates the sides of the rectangle and the capacitor plate. Nearby on the diagram there may be a letter designation of the device - QX.

How to check a quartz resonator

Problems with small appliances arise if they receive a strong shock. This happens when devices containing resonators fall. The latter fail and require replacement according to the same parameters.

Checking the resonator for functionality requires a tester. It is assembled according to a circuit based on the KT3102 transistor, 5 capacitors and 2 resistors (the device is similar to a quartz oscillator assembled on a transistor).

The device must be connected to the base of the transistor and the negative pole, protected by installing a protective capacitor. The power supply for the switching circuit is constant – 9V. Plus, a frequency meter is connected to the input of the transistor, and to its output through a capacitor, which records the frequency parameters of the resonator.

The diagram is used when setting up the oscillation circuit. When the resonator is working properly, when connected, it produces oscillations that lead to the appearance of an alternating voltage at the emitter of the transistor. Moreover, the voltage frequency coincides with a similar characteristic of the resonator.

The device is faulty if the frequency meter does not detect the occurrence of a frequency or detects the presence of a frequency, but it is either much different from the nominal value, or when the case is heated with a soldering iron, it changes greatly.

How to check a quartz resonator? Checking quartz resonators

Oscillations play one of the most important roles in the modern world. So, there is even the so-called string theory, which claims that everything around us is just waves. But there are other options for using this knowledge, and one of them is a quartz resonator. It happens that no matter what equipment sometimes breaks down, and they are no exception. How can you make sure that it is still working properly after a negative incident?

Let's say a word about the quartz resonator

A quartz resonator is an analogue of an oscillatory circuit based on inductance and capacitance. But there is a difference between them in favor of the first. As is clear, the concept of quality factor is used for the properties of an oscillatory circuit. In a quartz-based resonator, it achieves very large values ​​- in the range of 10 5 -10 7. In addition, it is more efficient for the entire circuit when temperature changes, which translates into longer service life for parts such as capacitors. The designation of quartz resonators in the diagram is in the form of a vertically placed rectangle, which is “sandwiched” on both sides by plates. From the outside, in the drawings, they resemble a hybrid of a capacitor and a resistor.

How does a quartz resonator work?

A plate, ring or bar is cut from a quartz crystal. At least two electrodes are applied to it, which are conductive strips. The plate is fixed and has its own resonant frequency mechanical vibrations. When voltage is applied to the electrodes, compression, shear, or bending occurs due to the piezoelectric effect (depending on how the quartz was cut). The oscillating crystal in such cases does work like an inductor. If the frequency of the voltage that is supplied is equal to or very close to its values, then the least amount of energy is required, with significant differences, to maintain operation. Now we can move on to the light of the main problem, which is why, in fact, this article about the quartz resonator is being written. How check its performance? 3 methods were selected, which will be discussed.

Method No. 1

Read also

Here the KT368 transistor plays the role of a generator. Its frequency is determined by a quartz resonator. When power is supplied, the generator starts working. It creates impulses that are equal to the frequency of its main resonance. Their sequence passes through a capacitor, which is designated as C3 (100r). It filters the DC component, and then transmits the pulse itself to an analog frequency meter, which is built on 2 D9B diodes and the following passive elements: capacitor C4 (1n), resistor R3 (100k) and a microammeter. All other elements serve to ensure the stability of the circuit and so that nothing burns out. Depending on the set frequency, the voltage on capacitor C4 may change. This is a fairly indicative method and its advantage is ease. And, accordingly, the higher the voltage, the higher the frequency of the resonator. But there are certain limitations: you should try it on this circuit only in cases where it is within the approximate range of 3 to 10 MHz. Examination quartz resonators, what goes beyond these values ​​usually does not fall under amateur radio electronics, but further consideration will be given to a drawing whose spectrum is 1-10 MHz.

How to check a quartz resonator

The usual scheme for checks quartz resonators, and if you add to the circuit multimeter with the ability to measure...

Checking quartz resonators

The usual scheme for checks performance of quartz resonators, as well as the possibility checks frequencies...

Method number 2

To increase accuracy, you can connect a frequency meter or oscilloscope to the output of the generator. Then it will be possible to calculate the desired indicator using Lissajous figures. But keep in mind that in such cases the quartz is excited, both at harmonics and at the fundamental frequency, which, in turn, can give a significant deviation. Look at the diagrams below (this one and the previous one). You see, there is various methods find the frequency, and here you have to experiment. The main thing is to follow safety precautions.

Checking two at once quartz resonators

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This circuit will allow you to determine whether two quartz resistors that operate in the range from 1 to 10 MHz are operational. Also, thanks to it, you can find out the shock signals that occur between frequencies. Therefore, you can not only find performance, but also select quartz resistors that are more suitable for each other in terms of their performance. The circuit is implemented with 2 master oscillators. The first of them works with a ZQ1 quartz resonator and is implemented on a KT315B transistor. So that check operation, the output voltage should be greater than 1.2 V, and press the SB1 button. The indicated indicator corresponds to the highest level signal and a logical unit. Depending on the quartz resonator, the required value for testing can be increased (the voltage can be increased each test by 0.1A-0.2V to that recommended in the official instructions for using the mechanism). In this case, output DD1.2 will be 1, and DD1.3 will be 0. Also, indicating the operation of the quartz oscillator, the HL1 LED will glow. The 2nd mechanism works similarly, and will be reported by HL2. If you start them right away, the HL4 LED will still glow.

When the frequencies of two generators are compared, their output signals from DD1.2 and DD1.5 are sent to DD2.1 DD2.2. At the outputs of the second inverters, the circuit receives a pulse-width modulated signal in order to compare the characteristics later. You can see this visually using the flickering LED HL4. To improve accuracy, add a frequency meter or oscilloscope. If the actual characteristics differ by kilohertz, then to determine a higher frequency quartz, press the SB2 button. Then the 1st resonator will reduce its values, and the tone of the light signal beats will be less. Then we can confidently say that ZQ1 has a higher frequency than ZQ2.

When checking always:

1. Read the annotation that the quartz resonator has;
2. Follow safety precautions.

Possible causes of failure

There are quite a lot of methods to display your own quartz resonator out of order. It’s worth getting acquainted with some of the most popular ones in order to avoid any problems in the future:

1. Falls from heights. The most popular reason. Remember: you should always contain workplace in perfect order and watch your actions.
2. The presence of constant tension. In general, quartz resonators are not afraid of it. But there were precedents. To check its functionality, turn on the 1000 mF capacitor one at a time - this step will return it to operation or avoid negative consequences.
3. Very large signal amplitude. This problem can be solved using various methods:

• Move the generation frequency slightly to the side so that it differs from the main indicator of the mechanical resonance of quartz. This is a more difficult option.
• Reduce the number of volts that power the generator itself. This is an easier option.
• Check if it's out quartz resonator really out of order. So, the reason for the decrease in activity may be flux or foreign particles (in this case, it must be thoroughly cleaned). It may also be that the insulation was used very intensively and it lost its characteristics. For a control check on this point, you can solder a “three-point” on the KT315 and check it with an axle (you can immediately compare the activity).

Modern digital equipment requires high precision, so digital devices often contain a quartz resonator, which is a stable and reliable generator of harmonic oscillations. Digital operate based on this constant frequency, and use it to operate the digital device. Quartz resonators are a reliable replacement for an oscillation circuit assembled on a capacitor and inductor.

The quality factor of the oscillation circuit based on the coil and capacitor does not exceed 300. It is a characteristic of the oscillation circuit that determines the value of the resonance band. The quality factor shows how many times the energy of the oscillatory system exceeds the energy loss during one oscillation period. The higher the quality factor, the less energy is lost in one period, and the slower the oscillations decay. The capacitance of a capacitor in a conventional circuit fluctuates depending on the temperature of the environment. The magnitude of the inductance of the coil also depends on many factors. There are even corresponding coefficients that determine the dependence of the parameters of these elements on temperature.

Quartz resonators, in contrast to the oscillation circuits described above, have a very high quality factor, reaching several million. At the same time, temperatures within -40 +70 degrees do not affect this parameter in any way. The high stability of quartz resonators at any temperature has led to their widespread use in digital electronics and radio engineering.

Varieties

By body type:

• For volumetric installation (cylindrical and standard).
• For surface mounting.

Based on body material:

• Metal.
• Glass.
• Plastic.

According to the body shape:

• Round.
• Rectangular.
• Cylindrical.
• Flat.

By the number of resonant systems:

• Single.
• Double.

For case protection:

• Sealed.
• Unsealed.
• Vacuum.

By purpose:

• Filter.
• Generating.

An important property of quartz resonators for successful operation is their activity. But it is not determined only by its own properties. The entire electrical circuit affects its activity.

The resonators used in filters use the same types of oscillations as in generator resonators. The filters use 2 and 4 electrode vacuum resonators. For multi-section filters, 4-electrode filters are most often used, as they are more economical.

Operating principle and device

Quartz resonators operate based on the piezoelectric effect formed on a quartz plate. Quartz is a natural crystal. It is a modification of a silicon-oxygen compound, and has the chemical formula Si O 2. The mass fraction of quartz in the earth's crust is about 60%, in free form 12%. Other minerals may also contain quartz.

Low-temperature quartz is used to produce quartz resonators. It has a pronounced piezoelectric effect. The chemical stability of quartz is very high; only hydrofluoric acid can dissolve quartz. In terms of hardness, quartz ranks second after diamond. A quartz plate for a resonator is made by cutting a piece of quartz at a given specific angle. Depending on this cutting angle, the quartz plate differs in different electromechanical parameters.

As a result, an oscillatory circuit is formed that has its own resonance frequency, which determines the operation of the entire resonator. If an alternating voltage with a resonance frequency is applied to the electrodes of the plate, a resonance effect will occur, and the amplitude of the plate’s vibrations will increase significantly. In this case, the resonator will reduce its resistance by a significant amount. This process is similar to the process that occurs in a series oscillation circuit (based on a coil and a capacitor). Energy losses when exciting a quartz resonator at the resonance frequency are very small, since the quality factor of the quartz oscillation circuit is very high.

This equivalent circuit consists of:

• R- Resistance.
• C1– Capacity.
• L– Inductance.
• C2– Static electric capacitance of the plates together with the holders.

These elements determine the electromechanical parameters of the quartz plate. If you remove the mounting elements, you get a consistent circuit LC. When installed on a circuit board, the quartz resonator does not tolerate excessive heat, since its design is very fragile. High heat can deform the holder and electrodes, which affects the functioning of the finished quartz resonator. Quartz completely loses its piezoelectric properties when heated to a temperature of 5370 degrees. However, the soldering iron is not capable of heating up that much.

On electrical diagrams, a quartz resonator is designated by analogy with a capacitor, but between the plates there is a rectangle symbolizing a quartz plate. In the diagram the resonator is marked “ QX».

Typically, the cause of a malfunction of a quartz resonator is a strong blow or fall of the device in which it is located. In this case, the resonator must be replaced with a new one with the same parameters. Such malfunctions occur in small devices that are easier to drop or damage. But such damage to resonators is not common, and usually the malfunction of the device lies in something completely different.

How to test quartz resonators

To check the resonator for its functionality, a special simple tester is assembled, which helps to check, in addition to the operation of the resonator, also its resonance frequency. The circuit of such a device is similar to a quartz oscillator assembled on a transistor.

By connecting the resonator between the negative pole and the base of the transistor through a protective capacitor, the resonance frequency is measured using a frequency meter. This circuit is suitable for tuning oscillation circuits. When the circuit is turned on, a working resonator creates oscillations. As a result, an alternating voltage appears at the emitter of the transistor with the resonance frequency of the resonator being tested.

If you connect a frequency meter to the output of the tester, you can measure the resonance frequency. With a stable frequency and slight heating of the resonator body, the frequency should not change significantly. If the frequency meter does not detect the occurrence of a frequency, or it changes greatly or differs greatly from the nominal value, then the resonator is unusable and requires replacement.

When using such a tester to configure circuits, capacitance C1 is required. But when checking the serviceability of resonators, its presence in the circuit is not required. In this case, the oscillating circuit is simply connected in place of the quartz resonator and the tester begins to create oscillations in the same way.

The tester, made according to the considered scheme, has proven itself well at a frequency of 15-20 megahertz. For other intervals, you can find other circuits assembled on microcircuits and other components.

Scope of application

Due to the stability of the parameters of quartz resonators, they have found wide use in various fields.

• Many measuring devices operate on the basis of such resonators, and the measurement accuracy is very high.
• The piezoquartz plate is used as a resonator in marine echo sounder to identify objects located in the water, study the seabed, determine the location of shoals and reefs. This makes it possible to study life in the ocean in deep-sea areas, as well as create accurate maps of the seabed.
• TO quartz resonators have found wide popularity in quartz watch , since the oscillation frequency of a quartz plate is practically independent of temperature and has a small relative change in frequency.

Quartz resonators are expanding their scope of use, the need for them is constantly increasing, as they have increased metrological parameters and operating efficiency.

Modern digital technology requires high precision, so it is not at all surprising that almost any digital device that catches the eye of the average person today contains a quartz resonator inside.

Quartz resonators at various frequencies are needed as reliable and stable sources of harmonic oscillations to digital microcontroller could rely on the reference frequency and operate with it in the future, in the process of work digital device. Thus, a quartz resonator is a reliable replacement for an oscillating LC circuit.

If we consider a simple oscillatory circuit consisting of and , it will quickly become clear that the quality factor of such a circuit in the circuit will not exceed 300, moreover, the capacitance of the capacitor will float depending on the ambient temperature, and the same will happen with the inductance.

It’s not for nothing that capacitors and coils have such parameters as TKE - temperature coefficient capacitance and TCI - temperature coefficient of inductance, showing how much the main parameters of these components change with a change in their temperature.

Unlike oscillatory circuits, quartz-based resonators have a quality factor unattainable for oscillatory circuits, which is measured in values ​​from 10,000 to 10,000,000, and there is no question of temperature stability of quartz resonators, because the frequency remains constant at any temperature value, usually from the range from - 40°C to +70°C.

Thus, due to their high temperature stability and quality factor, quartz resonators are used throughout radio engineering and digital electronics.

For the task clock frequency, he always needs a clock frequency generator on which he could reliably rely, and this generator always needs a high-frequency and, moreover, high-precision one. This is where a quartz resonator comes to the rescue. Of course, in some applications you can get by with piezoceramic resonators with a quality factor of 1000, and such resonators are sufficient for electronic toys and household radios, but for more precise devices quartz is needed.

The operation of a quartz resonator is based on the energy that appears on a quartz plate. Quartz is a polymorph of silicon dioxide, SiO2, and is found in nature in the form of crystals and pebbles. There is about 12% quartz in the earth's crust in its free form, in addition, quartz is also contained in the form of mixtures in other minerals, and in general there is more than 60% quartz in the earth's crust (mass fraction).

Low-temperature quartz, which has pronounced piezoelectric properties, is suitable for creating resonators. Chemically, quartz is very stable, and it can only be dissolved in hydrofluoric acid. Quartz is harder than opal, but not as hard as diamond.

When making a quartz plate, a piece is cut out of a quartz crystal at a strictly specified angle. Depending on the cut angle, the resulting quartz plate will differ in its electromechanical properties.

This results in an oscillatory system that has its own resonant frequency, and the quartz resonator obtained in this way has its own resonant frequency, determined by electromechanical parameters.

Now, if you apply an alternating voltage of a given resonant frequency to the metal electrodes of the plastic, the phenomenon of resonance will appear, and the amplitude of the harmonic oscillations of the plate will increase very significantly. In this case, the resistance of the resonator will greatly decrease, that is, the process is similar to what occurs in a series oscillatory circuit. Due to the high quality factor of such an “oscillatory circuit,” the energy losses during its excitation at the resonant frequency are negligible.

On the equivalent circuit: C2 - static electrical capacity of the plates with holders, L - inductance, C1 - capacitance, R - resistance, reflecting the electromechanical properties of the installed quartz plate. If you remove the mounting elements, you will be left with a series LC circuit.

During installation on printed circuit board, the quartz resonator cannot be overheated, because its design is quite fragile, and overheating can lead to deformation of the electrodes and holder, which will certainly affect the operation of the resonator in the finished device. If you heat quartz to 5730°C, it will completely lose its piezoelectric properties, but, fortunately, it is impossible to heat the element with a soldering iron to such a temperature.

The designation of a quartz resonator in the diagram is similar to the designation of a capacitor with a rectangle between the plates (quartz plate), and with the inscription “ZQ” or “Z”.

Often the cause of damage to a quartz resonator is a fall or strong impact of the device in which it is installed, and then it is necessary to replace the resonator with a new one with the same resonant frequency. Such damage is typical for small-sized devices that are easy to drop. However, according to statistics, such damage to quartz resonators is extremely rare, and more often the malfunction of the device is caused by another reason.

To check the quartz resonator for serviceability, you can assemble a small probe that will help not only make sure the resonator is working, but also see its resonant frequency. The probe circuit is a typical single-transistor crystal oscillator circuit.

Having turned on the resonator between the base and minus (you can use it through a protective capacitor in case of a short circuit in the resonator), all that remains is to measure the resonant frequency with a frequency meter. This scheme is also suitable for preset oscillatory circuits.

When the circuit is turned on, a working resonator will contribute to the generation of oscillations, and an alternating voltage can be observed at the emitter of the transistor, the frequency of which will correspond to the main resonant frequency of the quartz resonator being tested.

By connecting a frequency meter to the probe output, the user can observe this resonant frequency. If the frequency is stable, if slight heating of the resonator with a soldering iron does not lead to a strong frequency drift, then the resonator is working. If there is no generation, or the frequency floats or turns out to be completely different than it should be for the component under test, then the resonator is faulty and should be replaced.

This probe is also convenient for pre-tuning oscillatory circuits; in this case, capacitor C1 is required, although when checking resonators it can be excluded from the circuit. The circuit is simply connected in place of the resonator, and the circuit begins to generate oscillations in the same way.

A probe assembled according to the above circuit works remarkably well at frequencies from 15 to 20 MHz. For other ranges, you can always look for circuit diagrams on the Internet, fortunately there are many of them, both on discrete components and on a microcircuit.