The structure and properties of quartz crystal elements
One, quartz resonator.
Quartz crystal,also known as quartz resonator,is a kind of electric resonance element made by special cutting method based on the "piezoelectricity" characteristic of quartz. The quartz crystal element has the advantages of stable performance,high quality factor and small volume.
The structure and properties of quartz crystal elements.
The quartz crystal element is composed of a quartz wafer,a wafer bracket and a case.The role of the quartz crystal element in the circuit is equivalent to a high Q value LC resonant element.Because of the different azimuth in cutting quartz crystal,the quartz chips cut out are also different.The common cut types are AT, BT, DT, X, Y, etc.The performance of quartz chips with different cutting shapes is different,especially for the temperature characteristics of frequency.The wafer bracket is used to fix the wafer and the extraction electrode,and the wafer bracket has two kinds:the welding line type and the clamping type.The package of quartz crystal elements is glass vacuum seal,metal shell package,ceramic shell package and plastic case package.Quartz crystal elements generally have two electrodes,but there are also multi electrode packages.
Types and main parameters of quartz crystal components
Quartz crystal element type quartz crystal element with metal shell according to package shape, glass shell,Bakelite shell and plastic seal,etc;according to the frequency stability of quartz crystal components,there are ordinary type and high precision type,and are widely used in color TV,mobile phone,watch,radio,dVD player,etc.Although the classification of quartz crystal components is more,but the performance difference between each other is not big,as long as the volume and performance parameters are basically the same,many quartz crystal elements can be used interchangeably.
The main parameters of quartz crystal element are:nominal frequency, operating temperature,and frequency offset, temperature coefficient,load capacitance, excitation level,etc.
nominal frequency. There is a nominal frequency on the finished quartz crystal,which has the highest frequency stability when the circuit operates at this nominal frequency.This nominal frequency is usually measured on a quartz crystal with a certain load capacitance before the finished product is manufactured.
Load capacitance.
The so-called load capacitance of the quartz crystal refers to the equivalent capacitance of the past from the direction of the oscillating circuit from both ends of the crystal, that is,the sum of all the effective capacitors in and outside the integrated circuit, which is associated with the two ends of the crystal oscillator.
The name of the quartz crystal element
The naming of domestic quartz crystal elements is made up of 3 parts.The first part describes the material and shape of the shell with letters,such as the metal shell with J,s as the plastic shell,and B as the glass case. In the second part,the letters are used to indicate the cutting method of crystal chips,such as A,which indicates that the crystal cut is AT,and B indicates that the crystal is cut into BT type.Part 3 shows the main parameters of the quartz crystal element,such as the nominal operating frequency of the quartz crystal element,with a figure of 4.43361875.
Detection of quartz crystal elements
Quartz crystal is usually used to detect quartz crystal. In practice,it is more often used to replace quartz crystal to judge the quality of quartz crystal.
Resistance method.
Place the multimeter in the "RX10k" gear and measure the resistance between the two pins of the quartz crystal.It should be infinite.If the measured resistance value is not infinite,even if the resistance is zero,it is indicated that there are leakage or short circuit faults in the crystal.
In the way of road pressure measurement.
Taking the discrimination of the crystal of the color TV remote controller as an example, this paper introduces the concrete operation of this method.
The back cover of the remote control is opened,the position of the crystal and the negative end of the power supply are found.(both the 1.5V dry batteries are connected in series);the multimeter is placed in the DC 10V voltage shift,and the black pen is fixed in the negative end of the power supply.
First,in the case of not pressing the remote control key,the voltage value of the two pins of the crystal is measured with a red pen,and under normal circumstances,a foot is 0V,the other foot is about 3V ( supply voltage );then press any function key on the remote control,and then use the red pen to measure the voltage of the two pins of the crystal,under normal circumstances,both feet voltage is 1.5V ( half of the supply voltage ).If the difference between the calculated value and the normal value is large, the crystal work is not normal.
The electric pencil test method uses a test pencil to insert the cutter head into the fire wire hole of alternating current,and pinches any pin of the crystal by hand, touching the metal part of the top of the test pencil on the other pin,if the test pencil neon glows,it shows that the crystal is good,otherwise,the crystal is damaged.Ceramic components,SAW filters,and Hall element ceramic elements,like quartz crystal elements,are also fabricated using the " piezoelectric " effect,it is widely used in the radio receiving equipment,for example,different types of ceramic elements are used in the intermediate frequency amplifying circuit of color TV.