The challenging disk circuit component is mainly composed of a variety of data processing chips, driver chips, electronic elements and printed boards, as shown in Figure 1-8.



1.1.three.1 Different information processing chips and driver chips

1. Data processing chip and driver chip function

1) Motor drive chip

As shown in Figure 1-9, the drive chip applied to drive the spindle motor and voice coil motor of your tough disk. Since the speed of the existing tough disk is as well high, it is going to bring about the chip to create a big amount of heat, so the failure rate with the motor drive chip is higher.



two) Front signal processor

As shown in Figure 1-10, the pre-signal processor is utilized to course of action the signals in the magnetic head.



three) Interface chip CPU and digital signal processor

As shown in Figure 1-11, the interface chip CPU and digital signal processor are frequently integrated into 1 chip. As a result of the higher integration level, the damage rate is also high.



four) Cache circuit

As shown in Figure 1-12, the shape with the cache circuit is similar to the memory particles on the memory module, which is applied to speed up the information transmission speed on the hard disk. For the size on the cache capacity, unique brands and various models of goods are diverse. The early challenging disk caches have been basically really little, only a couple of hundred kilobytes, and could no longer meet the requirements of customers. Today's mainstream hard drives mainly use 2MB and 8MB cache, and you will discover merchandise with bigger cache capacity in servers or specific applications, even reaching 16MB, 64MB, etc.



five) BIOS

As shown in Figure 1-13, the BIOS chip is applied to save hard disk facts and is accountable for the difficult disk perform method.



2. Detection procedures of numerous information processing chips and driving chips

When repairing integrated circuit electronic products, judging the integrated circuit is definitely an essential content material, otherwise it is going to do much more with significantly less. Initially of all, we will have to master the purpose, internal structure principle, major electrical characteristics of your integrated circuit, and if important, analyze the internal circuit schematic diagram. Along with these, if you'll find DC voltages, waveforms, and forward and reverse DC resistance values ​​of each pin to ground, it truly is easier to judge, then figure out the fault place as outlined by the phenomenon, and after that come across the faulty element by location. At times numerous judgment approaches are required to prove whether or not the device is damaged. Frequently, you can find two solutions for checking and judging integrated circuits: a single is off-line judgment, that is definitely, the judgment that the integrated circuit will not be soldered in to the printed circuit board. Inside the absence of unique gear, it truly is crucial to determine the top quality of the integrated circuit. Difficult, generally, the DC resistance technique can be made use of to measure the forward and reverse resistance values ​​of every single pin corresponding towards the ground pin, and compared using the intact integrated circuit. You can also make use of the replacement method to insert the suspicious integrated circuit into the typical circuit. The position on the variety of integrated circuit is determined to figure out its excellent; the second is the on the internet inspection judgment, that may be, the judgment technique of your integrated circuit connected towards the printed circuit board. On the internet judgment may be the most practical and helpful method for repairing integrated circuit televisions. Several solutions are briefly described beneath.

1) Voltage measurement system

Use a multimeter to measure the DC working voltage worth of each pin to ground, then examine it together with the nominal value to judge the excellent with the integrated circuit in line with this, but to distinguish the non-faulty voltage error. When measuring the DC operating voltage of every pin from the integrated circuit, if the voltage with the individual pin meets the schematic diagram or the voltage worth marked inside the upkeep technical info doesn't match, don't rush to conclude that the integrated circuit is broken, the following components must be excluded initial Then make certain.

(1) Irrespective of whether the nominal voltage around the schematic diagram is wrong. Frequently you can find some manuals, schematic diagrams as well as other information marked having a huge difference among the actual voltage worth, and from time to time even wrong. At this time, it is best to find much more relevant facts for comparison, and if important, analyze the internal diagram and peripheral circuits, and calculate or estimate the marked voltage to verify whether the marked voltage is correct.

The nature with the nominal voltage should really be distinguished, that is certainly, regardless of whether the voltage is often a static functioning voltage or possibly a dynamic functioning voltage. Because the person pins of the integrated block differ significantly with the presence or absence in the injected signal, the channel switch could be set to an empty channel or perhaps a signal channel at this time to observe whether the voltage returns to typical. When the latter is normal, it indicates that the nominal voltage is usually a dynamic operating voltage, and this dynamic voltage refers to a certain condition. When testing, the dynamic voltage varies using the received field strength or the volume. .

(two) Variable components of peripheral circuits may result in alterations in pin voltage. When the measured voltage does not match the nominal voltage, it may be that person pins or peripheral circuits related for the pin are connected to a potentiometer with variable resistance (for example volume potentiometer, color saturation potentiometer, contrast possible And so on.). The position of these potentiometers is different, and the voltage of the pins is going to be substantially diverse. Hence, when the voltage of a specific pin does not match, the position in the pin or the potentiometer connected using the pin ought to be viewed as. See in the event the pin voltage is close to the nominal value.

(three) Different models have various values. Because the internal resistance from the multimeter head is different, or distinctive DC voltage blocks will trigger errors, the DC voltage marked on the basic schematic diagram is tested with the internal resistance in the test instrument greater than 20kΩ / V. When the internal resistance is much less than 20kΩ / V When the multimeter is tested, it will make the tested cashmere reduced than the originally marked voltage. In summary, when the integrated block isn't faulty, the measured outcome is various from the nominal value for some cause, so when testing the DC voltage or DC resistance in the integrated block, a test condition has to be specified. Especially when undertaking empirical information recording, we should really pay far more interest to this point. Normally turn each potentiometer to the mechanical middle position, the signal source adopts the normal color bar beneath a specific field strength, not surprisingly, if you can record the voltage worth of every potentiometer at the minimum and maximum at the identical time, it really is extra representative . If, just after excluding the above aspects, the measured individual pin voltage nevertheless will not match the nominal value, additional analysis from the cause is essential, but you can find only two possibilities: one is caused by the failure on the integrated circuit itself; the other will be the peripheral circuit on the integrated block Triggered. Ways to distinguish involving these two sources of failure may be the essential to repairing integrated circuits.

2) On-line direct present resistance measurement technique

In the event you find that the pin voltage is abnormal, you could initially test the high-quality with the peripheral components of your integrated circuit to identify no matter if the integrated circuit is broken. It truly is safer to measure the resistance value within the case of energy failure, and also you can verify the peripheral circuits from the integrated circuit on line without having information and data and with out understanding its operating principle. Within the relevant peripheral circuits, a speedy method is utilized to measure the peripheral elements to decide whether you'll find additional obvious faults. The technique is to measure the forward and reverse resistance values ​​of the diode along with the triode using a multimeter R × 10 block. At this time, since the electrical barrier is set incredibly low, the influence on the external circuit around the measurement data is smaller. It may be clearly noticed that the forward and reverse resistance values ​​of the diode and also the transistor, especially the forward resistance from the PN junction increases or the quick circuit is simple to find. Moreover, a general test could be made to determine irrespective of whether the inductor is open. Normally, the on-line DC resistance at both ends from the inductor is only a number of ohms to a few tens of ohms. The certain resistance is determined by the structure in the inductor. When the measured resistance at each ends is big, it can be concluded that the inductance is paralleled. Then, in line with the various parameters of your peripheral circuit components, unique electrical barriers are used to measure the capacitance and resistance, and verify regardless of whether there are actually clear quick circuits and open faults. Very first exclude the voltage modifications of person pins resulting from peripheral circuits, after which ascertain whether or not the integrated circuit is damaged.

3) Current flow tracking voltage measurement method

This process is according to the circuit composed from the internal and external components of the integrated circuit, along with the potential of every point is calculated or estimated with reference towards the provide voltage (the identified voltage with the main test point), then the integrated block is judged in accordance with regardless of whether the measured voltage meets the typical worth This method must have a comprehensive internal circuit diagram in the integrated block and a schematic diagram with the peripheral circuit.

four) On-line DC resistance measurement comparison approach

It uses a multimeter to measure the optimistic and damaging DC resistance of each pin with the integrated circuit to be checked against the ground and examine it with all the regular value to judge regardless of whether it is actually superior or terrible. This system could be the typical and reliable data of an integrated circuit on the very same model and model, so as to evaluate with all the information to be checked. When accumulating these standard data yourself, the following ought to be noted:

(1) The test situations need to be specified. Ahead of the test record, the model quantity, model and integrated circuit model of your tested machine must be recorded, along with the variable potentiometer in the circuit connected for the integrated circuit really should be set at the center of your machine. The data following the test should indicate the DC existing blocking position of your multimeter, which can be usually set at R × 1k or R × 10, along with the red test lead is grounded or the black test lead is grounded to measure two data.

(2) Interest need to be paid to errors triggered by measurement. The multimeter employed in the test ought to choose the internal resistance greater than or equal to 20kΩ / V, and confirm that the error value of the multimeter is inside the specified range, and attempt to examine the information together with the same multimeter as a great deal as possible.

(3) The circuit utilised for the original information should be the exact same because the circuit beneath test. Diverse grade models, however the exact same integrated circuit model, can still refer to. Diverse models and distinct circuits require to become distinguished, because the same integrated circuit can have unique connection strategies, and the resulting DC resistance values ​​are also distinct.

5) Non-online information and on the net information comparison approach

When the integrated circuit is not connected towards the peripheral circuit, the measured optimistic and unfavorable resistance values ​​of every pin corresponding to the ground pin are called off-line information. How to recover accidentally deleted Video files from SD Card -online information is hugely versatile and may be compared for different models, various circuits, and circuits with all the identical integrated circuit model. The certain measurement and comparison approaches are as follows: Very first, the ground pin from the integrated circuit to be checked must be detached in the printed circuit board with a hollow needle plus a soldering iron, and then the measurement and comparison ought to be performed corresponding to a suspected pin. If it is actually suspected that the pin has a little resistance connected in between ground and also the energy provide, in order not to impact the measured information, the pin also can be open to the printed board. As an example, for CA3065E, as long as the five pins ②, ⑤, ⑥, ⑨, and 12 are separated in the printed circuit board, each pin ought to be exactly the same as the original information with the non-in-circuit, otherwise, the integrated circuit is faulty.

6) Substitution system

Working with substitution technique to judge the quality of integrated circuits is actually a shortcut, which can lower all types of troubles caused by numerous inspection and analysis.

1.1.3.two Electronic components

1. Resistor

The resistor is actually a standard electronic component. The circuit symbol with the resistor is 'R', and its symbol and shape are shown in Figure 1-14.



1) Parameters of the resistor

(1) Nominal resistance: known as resistance, the fundamental unit is ohm (Ω). Generally utilised units are kilo-ohms (kΩ) and megohms (MΩ), that are in thousands. Nominal worth representation approaches contain direct regular method, colour typical technique, quick memory process, text symbol method, digital representation technique.

①Straight scale approach: On some substantial volume resistors, the nominal resistance value is directly marked with numbers, and some also straight mark the allowable deviation. As a consequence of the big size of your resistor, it's simple to mark, and it truly is also handy to work with. You are able to know the resistance worth at a glance.

②Color standard method: The colour common system uses the color circle or colour point (mainly the colour circle) to represent the nominal resistance and error on the resistor. You can find two kinds of color rings: four-color ring and five-color ring. When reading the colour ring, read in the finish of your resistor pin closest for the colour ring, which is the initial, second, and so on ... At present, the four colors are popular Ring resistor. Inside the four-channel colour circle resistor, the very first and second colour circles represent the helpful worth in the nominal resistance; the third colour circle represents the multiplication; the fourth color circle represents the allowable deviation. The which means of every color circle is shown in Table 1-1.



As an example, when the colour sequence in the colour circle is red, black, orange, and silver, the nominal resistance on the resistor is 20 × 103 ± 10%, that may be, 20kΩ ± 10%; the colour sequence of your color circle is green, blue, red, and silver. Then the nominal resistance from the resistor is 56 × 102 ± 10%, which is five.6kΩ ± 1%.

Within the five-channel colour wheel resistor, the initial 3 channels represent the productive value, the fourth channel would be the multiplier, as well as the fifth channel could be the allowable deviation. This is a representation of precision resistors. The successful number is three.

③Quick memory system: For the four-channel colour ring resistance, the third channel is mainly utilized. By way of example, if the third ring is silver, the resistance worth is 0.1Ω ～ 0.99Ω; gold is 1Ω ～ 9.9Ω; black is 10Ω ～ 99Ω; brown is 100Ω ～ 990Ω; red is 1kΩ ～ 99kΩ; orange is 10kΩ ～ 99kΩ; yellow It is 100kΩ990kΩ Green is 1MΩ ～ 9.9MΩ. For the five-ring resistance, the fourth ring could be the main, the same because the four-color ring resistance. It should really be noted that since the five-ring resistance can be a precision resistance, the volume is also small to identify which end may be the 1st ring, so the identification in the resistance worth of your colour ring resistance has to be measured with a multimeter.

④Character symbol strategy: mark the nominal resistance and allowable error on the resistor around the resistor with numbers and text symbols as outlined by a specific rule. The meaning with the unit initial letter symbol is shown in Table 1-2.



⑤Digital notation: three-digit number is made use of to represent the resistance worth (generally located in potentiometers, trimmer potentiometers and chip resistors), from left to ideal during identification, the initial and second digits are valid digits, the third digit is valid The multiplier of your value or the number of 0, the unit is really a couple of.

The quick memory system of digital representation of the same colour ring resistance, that's, the third digit is 1 is numerous hundred tens of ohms; 2 is a number of points and many thousand ohms; three is numerous dozens of ohms; four is Hundreds and tens of a huge number of ohms; 5 is actually a couple of megaohms ...

(2) Rated energy: Rated power refers towards the maximum power allowed within a precise ambient temperature variety. Within this energy limit, the resistor can function ordinarily with no altering its efficiency or getting broken. The approach for marking the rated energy of the resistor is shown in Figure 1-15.



(three) Resistance temperature coefficient: When the operating temperature changes, the resistance from the resistor may also transform accordingly, that is undesirable for general resistors. The temperature coefficient of resistance is employed to characterize the relative adjust in the resistance value when the operating temperature of the resistor alterations by 1 ° C. Certainly, the smaller sized the coefficient, the superior. The temperature coefficient of resistance is determined by the material utilised to create the resistor. There are two kinds of good and unfavorable coefficients. The former increases in resistance with rising temperature, as well as the latter decreases in resistance with increasing temperature. Thermistor is often a form of resistor created by using the house that its resistance adjustments with temperature.

two) Top quality inspection and measurement of resistors

Turn the function selection switch in the multimeter towards the electric block on the proper range, short-circuit the two test leads, adjust the 0Ω potentiometer to make the pointer from the meter point to 0, then execute the measurement. Note: Every single time the range is changed during the measurement, for instance, immediately after altering from R × 1 gear to R × ten gear or other gears, the measurement have to be performed immediately after re-zeroing.

Connect the two test leads (regardless of optimistic or damaging) to the two ends of the resistor to measure the actual resistance. So that you can improve the measurement accuracy, the variety need to be selected based on the nominal worth from the measured resistance. On account of the non-linear partnership in the ohm block scale, its middle section is relatively fine. Hence, the pointer indication worth ought to fall as far as you possibly can to the middle section of your scale, that is, within the array of 20% to 80% radian at the beginning in the complete scale to create the measurement much more correct. As outlined by the unique levels of resistance error, an error of ± 5%, ± 10% or ± 20% is permitted amongst the reading and the nominal resistance. If they do not match, and exceed the error variety, it signifies that the resistance has changed. When the measured result is 0, it suggests that the resistance has been short-circuited. If it really is infinity, it means that the resistance is broken and can no longer be utilized.

Matters needing interest throughout measurement: massive resistance resistor hands shouldn't touch the conductive parts on the test leads and resistors, because the human body includes a specific resistance, it's going to possess a certain impact around the test, even when the reading is also smaller. The detected resistance have to be soldered in the circuit, and no less than one head have to be soldered to avoid other elements within the circuit affecting the test and growing the measurement error, as shown in Figure 1-16.



2. Capacitor

1) Structure of the capacitor

The fixed capacitor is generally denoted by C. The circuit symbol and shape are shown in Figure 1-17. The fixed capacitor is composed of metal electrodes, dielectric layers and electrode leads. The dielectric supplies represented by numerous letters are shown in Table 1-3. Because an insulating dielectric layer is sandwiched involving the two metal electrodes, the two electrodes are insulated from each and every other. This structural feature determines the fundamental overall performance of fixed capacitors with 'DC blocking AC'. The polarity and voltage on the direct existing are fixed, so they can't pass by means of the capacitor, even though the polarity and voltage in the alternating present are frequently changing, which can continuously charge and discharge the capacitor to form a charge and discharge present. So, in this sense, alternating present can pass via capacitors.







2) Principal efficiency parameters

You'll find quite a few functionality parameters of capacitors. Right here are some normally applied parameters.

(1) Capacitance: Different capacitors have unique storage capacity. Usually the amount of charge stored when the capacitor is applied using a DC voltage of 1V is called the capacity with the capacitor, plus the simple unit would be the farad (F). In fact, Farad is definitely an uncommon unit, since the capacity of capacitors is often a great deal smaller sized than 1F, frequently utilised microfarad (μF), nanofarad (nF), picofarad (pF), etc., their connection is: 1F = 106μF , 1μF = 1000nF = 106pF.

You will find 3 main strategies for marking the capacitance of capacitors.

①Straight labeling system: The direct labeling technique utilizes numbers and letters to mark the specifications and models directly around the casing. This method is primarily used for bigger capacitors. The contents of capacity, withstand voltage, error, temperature variety, and so on. are often marked with numbers; the letters are employed to indicate the contents of dielectric supplies, packaging forms, and so forth. The letters are often divided into four components, the first component of the letter is generally fixed to C, indicating capacitance; the second letter indicates the dielectric material, the dielectric material represented by numerous letters is shown in Table 1-3; the third digit indicates the capacity; the fourth The position is indicated by letters, see Table 1-4.



Within the direct labeling process, 0 in integer units is generally omitted, by way of example, .22μF indicates 0.22μF; some use R to indicate the decimal point, for example, R33μF signifies 0.33μF.

② Text symbol method: The text symbol technique uses letters or numbers, and the labeling process makes use of a combination from the two to label the key parameters of your capacitor. There are two methods to indicate the capacity: a single should be to omit F, and use a mixture of numbers and letters. For instance, 10p represents 10pF, three.3μ represents 3.3μF, 3p3 represents 3.3pF, and 8n2 represents 8200pF. The second is represented by three digits, exactly where the very first and second digits are considerable digits, indicating the effective quantity of your capacity value; the third digit is the double price, indicating the number of zeros soon after the substantial digit, plus the unit of your capacitance is pFo. , 203 implies the capacity is 20 × 103pF = 0.02μF; 222 indicates the capacity is 22 × 102pF = 2200pF; 334 suggests the capacity is 33 × 104pF = 0.33μF and so on, this process is related towards the three-digit digital labeling system of resistance, no much more Narrate.

The text symbol approach commonly will not use a decimal point, but utilizes a unit integer to separate the decimal aspect. As an example, 2p2 = two.2pF; M33 = 0.33μF; 6n8 = 6800pF. Moreover, in the event the third digit is 9, it indicates 10-1 instead of 109. For example, 479 is expressed as 47 × 10-1pF = four.7pF.

③Color mark method: The color mark of your capacitor is similar for the resistance, as well as the unit is normally pF. For capacitors such as wafers or rectangular chips, the first ring could be the very first color ring, followed by the second colour ring, and the third colour ring ... The color ring capacitors are also divided into 4 rings or five rings, which can be far away The fifth ring or the sixth ring, these two rings often represent capacitance characteristics or operating voltage. The first and second (three, five-color rings) rings are substantial digits, the third (4, five-color rings) rings would be the quantity of 0s added later, along with the fourth (5, five-color rings) rings are errors. The worth of will be the exact same because the resistance with the color ring, the unit is pF. In addition, when the width of a particular colour circle is two or 3 instances wider than the common width, it indicates that this is 2 or 3 color circles from the similar color.

④Quick memory technique: the initial two significant digits, the third ring could be the added zero, then black is 10pF ～ 99pF; brown is 100pF ～ 990pF; red is 1000pF ～ 9900pF, orange is 0.01μF ～ 0.09μF; yellow is 0.1 μF ～ 0.9μF; green is 1μF ～ 9.9μF

Identification of the capacitance with the chip capacitor: Because the size from the chip capacitor is very small, the approach of labeling its capacity is somewhat diverse from that in the ordinary capacitor. The capacity code from the chip capacitor is usually composed of 3 digits, the unit is pF, the initial two digits are valid numbers, the third digit may be the number of 0 added, if there is a decimal point, it's represented by R. The identification of typically utilised chip capacitor capacity is shown in Table 1-5.



(two) Withstand voltage: The withstand voltage refers to the maximum DC voltage that the capacitor circuit can perform successfully for any extended time with no becoming broken down. For devices with the identical structure, medium and capacity, the larger the withstand voltage, the larger the volume.

In AC circuits, the withstand voltage of your capacitor really should be greater than the peak value of the circuit voltage, otherwise it might be broken down, along with the size of the withstand voltage depends on the dielectric material. When the voltage across the capacitor exceeds its rated voltage, the capacitor is going to be damaged by breakdown. The breakdown voltage of general electrolytic capacitors is 6.3V, 10V, 16V, 25V, 50V, 160V, 250V, and so on.

(3) Error: The maximum allowable deviation range among the actual capacitance and also the nominal capacitance could be the error. The error is normally divided into three levels: Class I ± 5%, Class II ± 10%, Class III ± 20%. In some cases, there is a level 0 with an error of ± 2%. The allowable error of precision capacitors is tiny, and also the error of electrolytic capacitors is significant. They use diverse error levels.

(4) Insulation resistance: Insulation resistance is applied to indicate the magnitude of leakage current. Usually, a small-capacity capacitor includes a big insulation resistance, that is a number of hundred megaohms or numerous gigaohms. The insulation resistance of electrolytic capacitors is generally little. In contrast, the higher the insulation resistance, the greater the leakage.

(5) Temperature coefficient: The temperature coefficient could be the relative alter value with the capacitance each time the temperature changes by 1 ° C inside a specific temperature range. The smaller the temperature coefficient, the much better. The basic working temperature variety is －55 ℃ ～ ＋ 125T

(six) Tolerance: refers to the potential of the capacitor to obstruct the alternating current, the unit is Europe, expressed by Xc, that is certainly



Xc could be the capacitive expansion to frequency, in hertz (Hz); c will be the capacity, in farads (F). In the above equation, the higher the frequency, the greater the capacity, the smaller sized the capacitive reactance.

three) Measurement of capacitor

(1) Detection of little capacitance below 100pF: Because the capacity on the fixed capacitor beneath 100pF is too little, use a multimeter to measure it, and only qualitatively verify whether it has leakage, internal short circuit or breakdown. Throughout the measurement, the multimeter Rxl0k block is usually selected, plus the two pins on the capacitor is often arbitrarily connected with two test leads, and the resistance worth should really be infinite. When the measured resistance worth (the pointer swings to the ideal) or the resistance worth is zero, it indicates that the capacitor leakage damage or internal breakdown.

(2) Detection of fixed capacitors above 0.01μF: For fixed capacitors above 0.01VF, the multimeter's R × 10k block is usually employed to straight test no matter if the capacitor is charging and whether there is certainly internal brief circuit or leakage, and may swing to the right according to the pointer The size estimates the capacity of the capacitor. Through the test operation, very first touch the two pins from the capacitor with two test leads, then modify the test leads and touch again. If the capacitance is superior, the pointer of your multimeter will swing towards the correct after which return towards the infinity position swiftly to the left. The greater the capacitance, the higher the amplitude of the pointer swing. If you repeatedly transform the meter pen to touch the two pins on the capacitor, the pointer of your multimeter will by no means swing towards the ideal, indicating that the capacitance in the capacitor is significantly less than 0.01μF or has disappeared. Within the measurement, if the pointer cannot swing back for the infinity position soon after swinging to the proper, it indicates that the capacitor is leaking or has broken down.

During the test, it should be noted that to be able to observe the scenario that the finger stick swings to the ideal, the test pen really should be repeatedly touched to measure the two pins of the capacitor until the capacitor is charged or not, as shown in Figure 1-18.



When working with the above approach for testing, you must spend interest to appropriate operation, and usually do not touch the two pins on the measured capacitor at the exact same time with your fingers. Otherwise, the resistance of the human body will influence the accuracy from the test and effortlessly lead to misjudgment. In particular when measuring using a higher resistance (R × 10k) of a multimeter, when the finger touches the two pins on the capacitor or the metal parts in the two test leads at the same time, the pointer is not going to return for the infinity position, causing the illusion from the tester and misunderstanding The leakage on the tested capacitor.

When measuring with a digital multimeter and electric bridge, the capacitor is usually directly inserted into the capacitor socket, and also the capacity could be study by putting the instrument within the corresponding gear.

(three) Detection process of electrolytic capacitor

The capacity of electrolytic capacitors is considerably larger than that of basic fixed capacitors. As a result, when measuring, the acceptable range should be chosen for distinct capacities. Generally, the capacitance among 1μF ～ 100μF can be measured with R × 100 ～ R × 1k block, and also the capacitance greater than 100F might be measured with R × one hundred ～ R × 1 block.

(1) Polarity discrimination: When discriminating in accordance with the pins, the lengthy feet are constructive plus the brief feet are damaging. For electrolytic capacitors with unclear optimistic and negative indicators, the above strategy of measuring leakage resistance could be utilized to judge. That is definitely, arbitrarily measure the leakage resistance, and then exchange the test results in measure once more. The black test lead using the largest resistance within the two measurements is connected for the positive electrode, and also the red test lead is connected to the adverse electrode.

(2) Leakage resistance: Connect the multimeter red bring about the damaging pole and also the black bring about the optimistic pole. At the moment of make contact with, the pointer in the multimeter deflects towards the right by a larger quantity (for the identical electrical block, the bigger the capacity, the larger the swing), and Turn left progressively till it stops at a particular position. The resistance at this time is the forward leakage resistance on the electrolytic capacitor. The larger the worth, the smaller sized the leakage present as well as the greater the capacitor functionality. Swap the red and black test leads, the multimeter pointer will repeat the above swing phenomenon. The measured resistance worth at this time is the reverse leakage resistance in the electrolytic capacitor. This value is much less than the forward leakage resistance, that is, the reverse leakage present is higher than the forward leakage present. In actual use, the leakage resistance on the electrolytic capacitor will have to not be as well huge, otherwise it's going to not function correctly. Within the test, if there is no charging phenomenon in both the direction plus the reverse direction, that may be, the watch needle doesn't move, it suggests that the capacity disappears or the internal circuit is open. The measured resistance worth is extremely smaller or zero, indicating that the capacitor has significant leakage or breakdown harm, and can no longer Use, as shown in Figure 1-19.



three. Inductor

1) Characteristics of inductor

When an alternating current passes by way of the coil, an alternating magnetic field is generated around the coil, causing the coil to produce an induced electromotive force. This induction phenomenon is named the self-induction phenomenon, and also the electromotive force it generates is called the self-induction electromotive force, and its magnitude is proportional for the rate of transform in the existing. The self-induced electromotive force usually attempts to stop the present inside the circuit from altering. The inductor has the characteristics of low frequency resistance, high frequency resistance, and direct present resistance and AC resistance. It may be combined with capacitors to kind tuners and filters, which play the function of frequency choice and frequency division. Just after energization, a magnetic field is generated around the inductive coil, which is usually employed to type an electromagnet, a relay, and so on. The alternating present coil and also the permanent magnet may be combined to form a speaker; let the coil move within the magnetic field with the permanent magnet (cutting the magnetic field line), along with the alternating present might be generated in the coil. Making use of this function, it might also be made into a microphone; The variable current will create an alternating magnetic field about the coil. In the alternating magnetic field, an induced electromotive force might be continuously generated at each ends from the coil. Making use of this function, the coil could be wound outdoors the iron core to create a transformer.

2) Inductor symbol

The inductance coil might be divided into fixed inductance and variable inductance and transformer. As outlined by the composition structure, it can be divided into 3 sorts: air core inductance, iron core inductance and magnetic core inductance coil. The letter symbol of your inductor coil is indicated by L. The circuit symbols and shapes of common inductors are shown in Figure 1-20.



three) Principal parameters and marking strategies of inductors

(1) Inductance: Inductance is definitely an crucial parameter in the inductor, its unit is Henry (H), known as Henry. Usually used units are millihenry (mH) and microhenry (PH), along with the partnership involving them is 1H = 103mH = 106μH.

The size of the inductance is connected for the number of turns (number of turns) of your inductor coil, the cross-sectional location of ​​the coil (the size from the coil), and no matter if there's an iron core or a magnetic core within the coil. For exactly the same type of coil, the more turns, the higher the inductance; the coils together with the identical number of turns have a higher inductance than the non-magnetic core (iron core).

There are actually two sorts of inductance labeling strategies: straight labeling process and colour circle marking approach.

①Straight typical strategy: The direct standard technique is always to directly mark the key parameters with the inductor, for instance inductance, error worth, and maximum DC operating present, on the shell with the inductor with text.

One example is, the inductor shell is marked with 3.9mH.A.II along with other words, indicating that its inductance is 3.9mH, the difference is class II (± 10%), and also the maximum functioning current is a block (50mA)

②Color mark technique: The colour mark strategy refers to printing different color rings around the outer shell from the inductor to mark its key parameters. The corresponding connection between colors and numbers is definitely the similar because the color circle resistance marking process, and their corresponding relationships are shown in Table 1-6.



Amongst them, the very first colour circle closest to a specific end represents the first important digit of inductance; the second colour circle represents the second substantial digit; the third color circle represents the energy of 10 or soon after the powerful digit Many 0s; the fourth 1 indicates the error, as well as the unit of inductance value is microhenry (μH). By way of example, the color circle mark of an inductor is brown, red, red, and silver, which means that its inductance is 12 × 102 = 1200μH, and also the allowable error is ± 10%.

(2) Rated existing: The rated existing refers for the maximum working current permitted when the inductor is working normally. When the operating existing is greater than the rated current, the inductor will alter parameters because of heat, and in severe cases it is going to be burned.

(3) Distributed capacitance: The distributed capacitance from the coil may be the capacitance in between the turns on the coil, involving the coil and ground, amongst the coil plus the shield, etc. Even though these capacitances are small, when the coil works in a high frequency band, The influence of distributed capacitance can not be ignored, they're going to have an effect on the stability and Q value with the coil. As a result, the smaller the distributed capacitance in the coil, the much better.

(four) Inductive reactance: refers towards the specific obstruction capacity on the inductive coil towards the alternating existing, expressed by XL, namely



XL is inductive reactance, unit is ohm (Ω); f is frequency, unit is hertz (Hz); L is inductance, unit is advantage (H). The larger L is plus the higher .f is, the bigger XL is.

(5) Allowable error: The allowable error of inductance is expressed by I, II and III, that are ± 5%, ± 10% and ± 20% respectively.

4. Inductor high-quality inspection and measurement

Inside the design of electronic circuits, it's normally necessary to measure the high quality and inductance of several coils. Inductance is normally measured with an oral meter or bridge tester, but these meters are difficult for individuals to personal. You will discover a lot of approaches to measure inductance having a multimeter.

When checking the high quality on the inductor, initially of all, you'll be able to verify whether or not there's any apparent abnormality by observing the look with the inductor. By way of example, regardless of whether the coil lead is broken or unsoldered, and irrespective of whether the magnet core is damaged or broken. Then the electrical resistance of your multimeter is usually used for detection, mainly to detect the winding on the inductive device, insulation as well as other situations.

(1) On-road detection. Set the multimeter to R × 1 or R × ten. The red and black test leads touch both ends in the coil. The hands should indicate conduction, otherwise the coil will break.

(two) Non-in-road detection. As shown in Figure 1-21, turn the multimeter to R × 1Ω block and accurately adjust the zero. Measure the resistance at each ends in the coil. When the coil is thinner or has more turns, the pointer need to possess a more clear swing, usually Amongst a few ohms to a dozen ohms; in the event the resistance is substantially smaller sized, the coil turns short-circuited. When the diameter from the coil is thick and the resistance worth is significantly less than 1Ω, it's not simple to study using the R × 1 block on the pointer multimeter, plus the ohm block with the digital multimeter can be applied rather. The resistance around 1Ω may be measured much more accurately. Note: The little value of your DC resistance on the tested inductor is related towards the diameter in the enameled wire applied to wind the inductor coil and the number of windings. So long as the resistance value is usually measured, the tested inductor is usually thought of regular.



five. diode

Crystal diodes are also named semiconductor diodes, or diodes for brief, and are semiconducting devices having a PN junction. There are a lot of types of diodes with various shapes and sizes. Normally employed are glass-shell diodes, plastic-encapsulated diodes, metal-shell diodes, high-power bolt-shaped metal diodes, miniature diodes, and chip diodes. In accordance with the function, it may be divided into detection diode, rectifier diode, voltage stabilizing diode, bidirectional diode, magnetic sensitive diode, photodiode, and switching diode.

1) Simple structure and symbol of ordinary diode

The circuit symbol with the diode is VD, and the circuit symbol and structure from the ordinary diode are shown in Figure 1-22.



A junction is formed in between the P region as well as the N area, which can be called a junction. https://en.wikipedia.org/wiki/Sd_card of the P and N regions are two electrodes. The two pins from the diode have constructive and unfavorable poles. Within the circuit symbol, the bottom on the triangle is optimistic, along with the end in the brief bar is adverse. In reality, some printed circuit symbols on the diode to mark the polarity; some printed a color circle on the negative finish on the diode as a damaging mark; some diodes have distinct shapes at both ends, a flat head can be a good pole, along with a round head is often a unfavorable pole. Consideration should be paid to identification.