How to measure the frequency of quartz. Quartz resonator - structure, principle of operation, how to check. Checking two quartz resonators at once

Quartz resonators, like most other radio components, it is desirable to check for performance before using them in amateur radio practice. One of the simplest schemes for such a probe was published in a Czech amateur radio magazine. The probe circuit is extremely simple to repeat, therefore it is of interest to a wide range of radio amateurs.

Scheme of a quartz resonator

Quartz resonators are among the simplest radio components, but radio amateurs have practically no instruments to test them before use. This sometimes leads to misunderstandings. Outwardly, the quartz resonator may not have any damage, but it does not work in the circuit. There can be many reasons for this. In particular, one of them is the fall of the resonator due to careless handling. It will help to make an initial check of quartz resonators even before they are used. simple design described in .

The tested quartz resonator is connected to contacts K2 (Fig. 1). A wide-range generator is made on transistor T1. It is designed to test quartz, the operating frequency of which is in the range of 1 ... 50 MHz. Having slightly changed the parameters of some radio components of the circuit, in particular. C2 and SZ. you can check other quartzes.

In the event that the quartz resonator is operational. on the emitter of the transistor T1 there is a high-frequency alternating voltage. It is rectified by diodes D1, D2, smoothed out by capacitor C5 and fed to the base of the key transistor T2, unlocking it. At the same time, the LED LD1 lights up.

What is a generator? A generator is essentially a device that converts one type of energy into another. In electronics, you can often hear the phrase “electrical energy generator, frequency generator,” and so on.

A quartz oscillator is a frequency generator and incorporates. There are basically two types of crystal oscillators:

those that can output a sinusoidal signal

and those that produce a square wave

The most commonly used square wave signal in electronics

Pierce scheme

In order to excite quartz at the resonance frequency, we need to assemble a circuit. The most simple circuit to excite quartz - this is a classic Pierce generator, which consists of only one field effect transistor and a small strapping of four radio elements:

A few words about how the scheme works. The diagram has a positive Feedback and self-oscillations begin to appear in it. But what is positive feedback?

At school, all of you were vaccinated for the Mantoux reaction to determine if you had a tube or not. After a while, nurses came and measured your skin reaction to this vaccine with a ruler.

When this vaccine was given, it was impossible to scratch the injection site. But I, then still a greenhorn, was on the drum. As soon as I started to quietly scratch the injection site, I wanted to scratch even more)) And now the speed of the hand that scratched the vaccine froze at some peak, because I was able to oscillate with my hand at a maximum frequency of 15 Hertz. Vaccination I swelled on the floor of my arm)) And even once they took me to donate blood on suspicion of tuberculosis, but as it turned out, they didn’t find me. It's not surprising ;-).

So what am I telling you here jokes from life? The fact is that this scabies vaccination is the most positive feedback. That is, while I did not touch it, I did not want to scratch it. But as soon as I scratched softly, it began to itch more and I began to scratch more, and itching became even more, and so on. If there were no physical restrictions on my hand, then for sure, the vaccination site would have already been worn down to the meat. But I could only wave my hand at a certain maximum frequency. So, the quartz oscillator has the same principle ;-). I gave a little impulse, and it starts to accelerate and already stops only at the parallel resonance frequency ;-). Let's just say "physical limitation".

First of all, we need to choose an inductor. I took a toroidal core and wound several turns from the MGTF wire

The whole process was controlled using an LC meter, achieving a nominal value, as in the diagram - 2.5 mH. If it didn’t get enough, he added turns, if he overdid the face value, then he reduced it. As a result, I achieved the following inductance:

Its correct name is .

Pinout from left to right: Drain - Source - Gate

A small lyrical digression.

So, we assembled a quartz oscillator, applied voltage, it remains only to remove the signal from the output of our self-made generator. Digital oscilloscope takes over

First of all, I took the quartz to the highest frequency that I have: 32,768 megahertz. Do not confuse it with watch quartz (about him will be discussed below).

In the lower left corner, the oscilloscope shows us the frequency:

As you can see 32.77 megahertz. The main thing is that our quartz is alive and the circuit works!

Let's take quartz with a frequency of 27 megahertz:

My readings fluctuated. Screenshot what I did:

The frequency is also more or less shown correctly.

Well, similarly, we check all the other quartz that I have.

Here is an oscillogram of quartz at 16 megahertz:

The oscilloscope showed a frequency of exactly 16 megahertz.

Here I set quartz to 6 megahertz:

Exactly 6 megahertz

At 4 megahertz:

All OK.

Well, let's take another Soviet one at 1 megahertz. This is how it looks like:

Above it says 1000 Kilohertz = 1MegaHertz ;-)

Let's look at the waveform:

Worker!

With a strong desire, you can even measure the frequency with a Chinese frequency generator:

400 Hertz error for an old Soviet quartz is not very much. But it's better, of course, to use a normal professional frequency meter ;-)

watch quartz

With clock quartz, the crystal oscillator according to the Pierce scheme refused to work.

“What is watch quartz?” - you ask. Watch quartz is a quartz with a frequency of 32,768 Hertz. Why does it have such a strange frequency? The point is that 32 768 is 2 15 . Such quartz works in tandem with a 15-bit counter chip. This is our K176IE5 chip.

The principle of operation of this microcircuit is as follows:After it has counted 32,768 pulses, it gives out a pulse on one of its legs. This impulse on a leg with a quartz resonator at 32,768 Hertz appears exactly once per second. And as you remember, an oscillation once per second is 1 Hertz. That is, on this leg, the pulse will be issued at a frequency of 1 Hertz. And if this is the case, then why not use it in hours? Hence the name -.

Currently, in wristwatches and other mobile gadgets, this counter and quartz resonator are built into one microcircuit and provide not only counting seconds, but also a number of other functions, such as an alarm clock, calendar, etc. Such microcircuits are called RTC (R eaal T ime C lock) or translated from the bourgeois Real Time Clock.

Pierce's circuit for a square wave

So, back to Pierce's scheme. Pierce's previous circuit generates a sinusoidal signal

But there is also a modified Pierce circuit for a square wave

And here she is:

The denominations of some radioelements can be changed in a fairly wide range. For example, capacitors C1 and C2 can range from 10pF to 100pF. Here the rule is this: the lower the frequency of the quartz, the lower the capacitance of the capacitor should be. For watch quartz, capacitors can be supplied with a nominal value of 15-18 pF. If quartz with a frequency of 1 to 10 megahertz, then you can put 22-56 pF. If you don't want to bother, then just put 22 pF capacitors. You won't guess right.

Also a small note to note: by changing the value of the capacitor C1, you can adjust the resonance frequency in very thin limits.

Resistor R1 can be changed from 1 to 20 MΩ, and R2 from zero to 100 kΩ. There is also a rule here: the lower the frequency of the quartz, the greater the value of these resistors and vice versa.

The maximum crystal frequency that can be inserted into the circuit depends on the speed of the CMOS inverter. I took the 74HC04 chip. She's not very fast. It consists of six inverters, but we will use only one inverter:

Here is her pinout:

By connecting clock quartz to this circuit, the oscilloscope produced the following waveform:

By the way, does this part of the scheme remind you of anything?

Isn't this part of the circuit used to clock AVR microcontrollers?

She is the best! It's just that the missing elements of the circuit are already in the MK itself ;-)

Advantages of crystal oscillators

The advantages of quartz frequency generators are high frequency stability. Basically, it is 10 -5 - 10 -6 of the nominal or, as they often say, ppm (from the English. parts per million)- parts per million, that is, one millionth or a number of 10 -6. The frequency deviation in one direction or another in a quartz oscillator is mainly due to changes in ambient temperature, as well as to the aging of quartz. With the aging of quartz, the frequency of the quartz oscillator becomes a little less every year by about 1.8x10 -7 of the nominal value. If, say, I took a quartz with a frequency of 10 Megahertz (10,000,000 Hertz) and put it in the circuit, then in a year its frequency will go down by about 2 Hertz ;-) I think it's quite tolerable.

Currently, quartz oscillators are produced in the form of finished modules. Some firms producing such generators achieve frequency stability up to 10 -11 of the nominal value! Look ready-made modules like that:

or so

Such crystal oscillator modules generally have 4 outputs. Here is the pinout of the square crystal oscillator:

Let's check one of them. It says 1 MHz

Here is his back view:

Here is his pinout:

By applying a constant voltage from 3.3 to 5 Volts plus by 8, and minus by 4, from output 5 I got a clean, even, beautiful meander with a frequency written on a quartz oscillator, that is, 1 Megahertz, with very small emissions.

Well, look at it!

Yes, and the Chinese generator-frequency meter showed the exact frequency:

From this we conclude: it is better to buy a ready-made quartz oscillator than to kill a lot of time and nerves yourself to set up Pierce's circuit. Pierce's circuit will be suitable for testing resonators and for your various DIY projects.

A resonator is a system capable of oscillatory movements with a maximum amplitude under certain conditions. Quartz resonator - a plate of quartz, usually in the form of a parallelepiped, acts like this when an alternating current is applied (the frequency is different for different plates). The working frequency of this part is determined by its thickness. The dependence is inverse here. The thinnest plates have the highest frequency (not exceeding 50 MHz).

In rare cases, you can achieve a frequency of 200 MHz. This is only valid when operating at an overtone (a non-fundamental frequency that is higher than the fundamental). Special filters are able to suppress the fundamental frequency of the quartz plate and highlight the overtone multiple of it.

Only odd harmonics (another name for overtones) are suitable for work. In addition, when using them, the frequency readings increase at lower amplitudes. Usually, a ninefold decrease in wave height becomes the maximum. Further, it becomes difficult to detect changes.

Quartz is a dielectric. In combination with a pair of metal electrodes, it turns into a capacitor, but its capacity is small and there is no point in measuring it. In the diagram, this part is displayed as a crystalline rectangle between the capacitor plates. A quartz plate, like other elastic bodies, is characterized by the presence of its own resonant frequency, which depends on its size. Plates of small thickness have a higher resonant frequency. As a result: it is only necessary to choose a plate with parameters such that the frequency mechanical vibrations would coincide with the frequency of the alternating voltage applied to the plate. Quartz plate, only suitable when using alternating current, because D.C. can provoke only a single compression or decompression.

As a result, it is obvious that quartz is a very simple resonant system (with all the properties inherent in oscillatory circuits), but this does not at all reduce the quality of its work.

The quartz resonator is even more efficient. His quality factor is 10 5 - 10 7 . Quartz resonators increase the overall life of the capacitor due to their thermal stability, durability and manufacturability. Ease of use is added by the small size of the parts. But the most important advantage is the ability to provide a stable frequency.

Among the minuses are only the narrowness of the range of attunement of the available frequency with the frequency of external elements.

In any case, quartz resonators are very popular and are used in watches, numerous radio electronics and other devices. In some countries, quartz plates are installed directly on the sidewalks, and people produce energy just by walking back and forth.

Principle of operation

The functions of the quartz resonator are provided by the piezoelectric effect. This phenomenon gives rise to electric charge in the event that mechanical deformation of some types of crystals occurs (natural ones include quartz and tourmaline). The force of the charge in this case is directly dependent on the force of deformation. This is called the direct piezoelectric effect. The essence of the inverse piezoelectric effect is that if an electric field is applied to the crystal, it will deform.

Health check

There are several simple methods for checking the condition of quartz in a movement. Here are a couple of them:

1. To accurately determine the state of the resonator, you will need to connect an oscilloscope or frequency meter to the generator output. The required data can be calculated using Lissajous figures. However, under such circumstances, it is possible to inadvertently excite the oscillatory motions of quartz both at overtonic and at fundamental frequencies. This can create measurement inaccuracies. This method can be used in the range from 1 to 10 MHz.
2. The frequency of the generator depends on the quartz resonator. When energy is applied, the generator produces pulses that coincide with the frequency of the main resonance. A series of these pulses is passed through a capacitor, which filters out the constant component, leaving only overtones, and the pulses themselves are transmitted to an analog frequency meter. It can be easily constructed from two diodes, a capacitor, a resistor and a microammeter. Depending on the frequency readings, the voltage across the capacitor will also change. This method also does not differ in accuracy and can only be used in the range from 3 to 10 MHz.

In general, a reliable check of quartz resonators can only be carried out when they are replaced. Yes, and to suspect a breakdown of the resonator in the mechanism is only in the most extreme case. Although portable electronics subject to frequent drops, this does not apply.

Fluctuations are given one of the most important roles in 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 just so happens that any technique periodically fails, and they are no exception. How to make sure that after a negative incident it still works as it should?

Let's say a word about the quartz resonator

A quartz resonator is an analog of an oscillatory circuit based on inductance and capacitance. But there is a difference between them in favor of the first. As you know, to characterize the oscillatory circuit, the concept of quality factor is used. In a resonator based on quartz, it reaches very high values ​​- in the range of 10 5 -10 7 . In addition, it is more efficient for the entire circuit when the temperature changes, which affects the longer life of parts such as capacitors. The designation of quartz resonators in the diagram is carried out in the form of a vertically located rectangle, which is “clamped” by plates on both sides. Outwardly, 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 out of 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 of mechanical vibrations. When voltage is applied to the electrodes, due to the piezoelectric effect, compression, shearing or bending occurs (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 own values, then less energy is required with significant differences to maintain operation. Now we can move on to highlighting the main problem, which, in fact, is why this article is being written about a quartz resonator. How to check its performance? 3 methods were selected, which will be discussed.

Method number 1

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 to work. It creates impulses that are equal to the frequency of its main resonance. Their sequence passes through the capacitor, which is designated as C3 (100r). It filters the DC component, and then the pulse itself is transmitted to an analog frequency meter, which is built on two D9B diodes and such passive elements: capacitor C4 (1n), resistor R3 (100k) and a microammeter. All other elements serve for the stability of the circuit and so that nothing burns out. Depending on the set frequency, the voltage that is on the capacitor C4 can change. This is a fairly approximate 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 if it is in the approximate range of three to ten MHz. Checking quartz resonators that goes beyond these values ​​\u200b\u200busually does not fall under amateur radio electronics, but a drawing will be considered below, which has a range of 1-10 MHz.

Method number 2

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

Checking two quartz resonators at once

This circuit will allow you to determine whether two quartz resistors that operate within one to ten MHz are operational. Also, thanks to it, you can recognize the shock signals that go between frequencies. Therefore, you can not only determine the performance, but also select quartz resistors that are most suitable for each other in terms of their performance. The circuit is implemented with two master oscillators. The first of them works with a ZQ1 quartz resonator and is implemented on a KT315B transistor. To check the performance, the output voltage must be greater than 1.2 V, and you should press the SB1 button. The specified indicator corresponds to a high level signal and a logical unit. Depending on the quartz resonator, the required value for testing can be increased (it is possible to increase the voltage for each test by 0.1A-0.2V to the recommended value in official instructions on the use of the mechanism). In this case, the output DD1.2 will have 1, and DD1.3 - 0. Also, reporting on the operation of the crystal oscillator, the HL1 LED will light up. The second mechanism works similarly and will be reported by HL2. If they are started at the same time, the HL4 LED will still be on.

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 then compare the performance. You can see this visually by blinking the HL4 LED. To improve accuracy, add a frequency counter or oscilloscope. If the real indicators differ by kilohertz, then to determine a higher-frequency quartz, press the SB2 button. Then the first resonator will decrease its values, and the tone of the beats of the light signals will be less. Then we can confidently say that ZQ1 is more high-frequency than ZQ2.

Features of checks

When checking always:

1. Read the instructions that the quartz resonator has;
2. Stick to safety precautions.

Possible causes of failure

There are quite a few ways to disable your quartz resonator. Some of the most popular are worth checking out in order to avoid any problems in the future:

1. Falls from a height. The most popular reason. Remember: it is always necessary to keep the workplace in perfect order and monitor your actions.
2. The presence of a constant voltage. In general, quartz resonators are not afraid of it. But there were precedents. To check the performance, turn on a 1000 mF capacitor in series - this step will return it to operation or avoid negative consequences.
3. Signal amplitude too high. You can solve this problem in different ways:

• Take the generation frequency a little to the side so that it differs from the main indicator of the mechanical resonance of quartz. This is a more difficult option.
• Lower the number of volts that feed the generator itself. This is an easier option.
• Check if the quartz resonator is really out of order. So, the reason for the drop in activity may be flux or foreign particles (in this case, it is necessary to clean it thoroughly). It may also be that the insulation has been used too actively, and it has lost its properties. For a control check on this item, you can solder a “three-point” on KT315 and check with an axle (at the same time, activity can be compared).

Conclusion

The article discussed how to check the performance of such elements. electrical circuits, as the frequency of a quartz resonator, as well as their property. Ways of establishing the necessary information were discussed, as well as possible reasons why they fail during operation. But to avoid negative consequences, always work with a clear head - and then the work of the quartz resonator will be less disturbing.

Quartz resonator how to check? Checking quartz resonators

Fluctuations are given 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 technique fails from time to time, and they are no exception here. How to make sure that after a negative incident it still works as it should?

Let's say a word about the quartz resonator

A quartz resonator is an analog of an oscillatory circuit based on inductance and capacitance. But between them there is a difference in favor of the first. As is clear, for the property of the oscillatory circuit, the concept of quality factor is used. In a resonator based on quartz, it achieves very large values ​​- in the range of 10 5 -10 7 . In addition, it is more efficient for the entire circuit when the temperature changes, which affects the longer life of parts such as capacitors. The designation of quartz resonators in the diagram is carried out in the form of a vertically placed rectangle, which is “clamped” by plates on both sides. Outwardly, 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 out of 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 of mechanical vibrations. When voltage is applied to the electrodes, due to the piezoelectric effect, compression, shear, or bending occurs (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 you can run across to the light of the main obstacle, because of which, in fact, this article is being written about the quartz resonator. How check its performance? 3 methods were selected, which will be discussed.

Method number 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 to work. It creates impulses that are equal to the frequency of its main resonance. Their sequence passes through the capacitor, which is designated as C3 (100r). It filters the DC component, and then the pulse itself is transmitted to an analog frequency meter, which is built on 2 D9B diodes and such passive elements: capacitor C4 (1n), resistor R3 (100k) and a microammeter. All other elements serve for the stability of the circuit and so that nothing burns out. Depending on the set frequency, the voltage that is on the capacitor C4 can 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 if it is in the approximate range from 3 to 10 MHz. Examination quartz resonators, which goes beyond these values, usually does not fall under amateur radio electronics, but a drawing with a spectrum of 1-10 MHz will be further considered.

How to test a quartz resonator

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

Checking quartz resonators

The usual pattern for checks performance of quartz resonators, as well as the possibility checks frequency...

Method number 2

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

Checking two at once quartz resonators

Read also

This circuit will allow you to find if 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 go between frequencies. Therefore, you can not only find operability, 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 performance, the output voltage must be greater than 1.2 V, and you should press the SB1 button. The indicated indicator corresponds to the signal of the highest level and a logical unit. Depending on the quartz resonator, the required value for checking can be increased (you can increase the voltage for each check by 0.1A-0.2V to that recommended in the official annotation on using the mechanism). With all this, the output DD1.2 will have 1, and DD1.3 - 0. Also, reporting on the operation of the quartz oscillator, the HL1 LED will light up. The 2nd mechanism works similarly and will be reported to HL2. If you start them immediately, then the HL4 LED will still be lit.

When the frequencies of 2 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 visually see this with the help of the flickering of the HL4 LED. To improve accuracy, add a frequency meter or an oscilloscope. If the actual characteristics differ by kilohertz, then to determine a more frequency quartz, press the SB2 button. Then the 1st resonator will decrease its values, and the tone of the beats of the light signals will be less. Then we can confidently say that ZQ1 is more frequent than ZQ2.

When checking always:

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

Possible causes of failure

There are many ways to get your own quartz resonator out of service. It is worth familiarizing yourself with some of the most popular ones in order to avoid any troubles in the future:

1. Falls from a height. The most popular reason. Remember: you always need to keep the workplace in perfect order and watch your actions.
2. The presence of constant voltage. In general, quartz resonators are not afraid of it. But there were precedents. To check the performance, turn on the 1000 mF capacitor in turn - this step will return it to operation or avoid negative consequences.
3. Very high signal amplitude. This problem can be solved in various ways:

• Take the generation frequency a little 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 feed the generator itself. This is an easier option.
• Check if it's out quartz resonator really out of order. So, a prerequisite for a drop in activity may be a flux or foreign particles (in this case, it must be perfectly cleaned). It may also be that the insulation has been used very intensively, and it has lost its characteristics. For a control check on this point, you can solder a “three-point” on KT315 and check with an axle (you can immediately compare activity).