Detection methods of electronic components in electronic circuits

In electronic circuits, in addition to the electronic components (such as resistors, capacitors, inductors, diodes, triodes, integrated circuits, etc.), there are other commonly used electronic components, such as electroacoustic devices, connectors and switches.

1 electroacoustic device

Electroacoustic device refers to the device that can convert electroacoustic into audio electrical signal or audio electrical signal into sound energy. The common electroacoustic devices include loudspeakers, microphones, earphones, etc.

1.1 loudspeaker

General detection of high, medium and low-frequency speaker visual judgment: because the test of the effective frequency range of the speaker is more troublesome, so more according to its aperture size and the softness of the paper basin to make intuitive judgment, in order to roughly determine its frequency response. Generally speaking, the larger the diameter of the speaker, the softer the edge of the paper basin, and the better the low-frequency characteristics. On the contrary, the smaller the diameter of the speaker, the harder and lighter the paper basin, and the better the high-frequency characteristics.

Check the sound quality: use the R × 1 Ω gear of the multimeter to measure the impedance of the loudspeaker. As soon as the pen touches the pin, you can hear the click sound. The louder the click sound is, the higher the efficiency of electricity sound conversion is. The clearer and cleaner the click sound is, the better the sound quality is. If the pointer of the multimeter does not swing when touching, it indicates that the voice coil or voice coil lead of the loudspeaker is open circuit; if only the pointer swings, but there is no click, it indicates that the voice coil lead of the loudspeaker is short circuit.

1.2 microphone

General detection: the moving coil microphone can be simply judged with a multimeter (capacitive microphone should not be measured with a multimeter). When measuring, put the multimeter in the R × 10 Ω or R × 100 Ω position, and connect the two pins with the two ends of the microphone plug. At this time, the multimeter should have a certain DC resistance indication. The high impedance microphone is about 1 ~ 2 K Ω, and the low impedance microphone is about tens of Ω. If the resistance is zero or infinite, it means that there may be a short circuit or an open circuit inside the microphone.

1.3 headphones

General test: commonly used headphones are divided into high impedance and low impedance. High impedance earphone is generally 800 ~ 2000 Ω, low impedance earphone is generally about 8 Ω. If it is found that the earphone is silent but the sound source is good, it can be measured with the help of a multimeter.

When checking the low impedance earphone, the R × 1 Ω gear of the multimeter can be used. The method can refer to the method of using the multimeter to judge whether the loudspeaker is good or bad.

When the high impedance headphone multimeter is used to measure, set the multimeter to R × 100 Ω. Generally, the pointer of the meter head points to about 800 Ω. If the pointer points to r = 0 or the pointer does not deflect, it indicates that there is a fault. At this time, the terminal in the headphone may be short-circuit or open circuit. After unscrewing the earphone plug, if the wiring on the terminal is correct, it means that the earphone coil is faulty.

Stereo headphones are generally three core plugs, one of which is R channel and the other is L channel. In short, it's equal to two earphones, so it's OK to check them separately.

2 general detection and selection of connectors and switches

The general key points of connector and switch detection are reliable contact and accurate conversion. Generally, the requirements can be achieved by visual inspection and multimeter measurement.

(1) visual inspection

The appearance of unsealed switches and connectors can be inspected first. The main work in the inspection is to check whether the whole is complete, whether there is damage, whether there is damage, deformation, looseness, oxidation or loss of elasticity in the contact part, and whether the positioning of the band switch is accurate, whether there is dislocation, short circuit, etc.

(2) measure with a multimeter

Put the multimeter at R × 1 Ω and measure the DC resistance between the two contacts. The resistance should be zero, otherwise it means that the contact is not in good contact. Put the multimeter at R × 1 K Ω or R × 10 K Ω, measure the resistance between contacts and between contacts and "ground" after the contact is disconnected, and the value should tend to infinity, otherwise it indicates that the insulation performance of switch and connector is not good.