Plug the need to wear anti-static clothing, anti-static shoes, wear PU nylon coated gloves

According to the work frequency is different, can be divided into high-frequency connectors and low-frequency connectors. Low-frequency connector is usually referred to as the frequency of 100MHz below the connector; high-frequency connector refers to the frequency of 100MHz or more connectors, such connectors will consider the structure of high-frequency anti-static shoes, PU nylon coated gloves, Anti-static clothing electric field leakage, reflection and other issues.

According to the different structure, can be divided into circular connectors, rectangular connectors, printed circuit board connectors, ribbon flat cable connector, and so on.

Several commonly used connectors

Round connector: also known as aviation plug, socket, it has a standard screw locking mechanism, the number of contacts from two to hundreds of range.

Rectangular connector: Rectangular connector rectangular arrangement can take full advantage of space, and the current capacity is also large, so it is widely used in the machine amps level current signal interconnection.

Printed board connector: In order to facilitate the replacement of printed circuit board, maintenance, printed circuit board or printed circuit board and other parts of the interconnection between the commonly used printed circuit board connector, according to its structure is divided into spring Chip and pinhole type.

Ribbon flat cable connector: ribbon flat cable connector is made of dozens of wires with PVC as the insulation layer side by side bonding together. It takes a small space, light and flexible, easy wiring, not easy to confuse.

Detection of switch parts and connectors

Switch parts and connectors of the detection points are reliable contact, accurate conversion, generally measured with a multimeter and multimeter to meet the requirements. The first is the appearance of inspection, non-sealed switch parts, connectors can be the first appearance inspection, mainly to check whether the integrity of the whole, with or without damage, contact with some damage, deformation, loosening, oxidation or loss of flexibility, But also check the positioning is accurate, with or without dislocation, short circuit and so on. Followed by contact resistance, insulation resistance, the multimeter placed in the month × 1Q block, measured connected between the two contacts DC resistance, the resistance should be close to zero, otherwise the contact contact is bad. The multimeter placed in the R × 1k or foot × 10k block, measuring contact contact after the contact asked, the contact on the "ground" asked the resistance,

This value should tend to infinity, otherwise the switch, connector insulation performance is not good. The third test load capacity, that is, the connector under the specified conditions, can be given at a given voltage under the rated current value. The fourth detection of mechanical properties, the crimping of the terminal installed in the shell of anti-static shoes, anti-static clothing, and remove the external lock and the socket along the axial insertion and removal of the required force and pull out force, The insertion force. The minimum tension required to fasten the connector in the housing and pull the wire body at a constant speed in the direction of the connector to remove the connector from the housing is the terminal retention force. Fix the needle seat and apply the thrust from the top to the pin so that the thrust required to displace the pin and the housing is the pin retention force.

Electro-acoustic devices are devices that can be converted between electrical and acoustic signals. Commonly used electro-acoustic devices are microphones, speakers and headphones.

1. microphone

1) the type of microphone and circuit symbols

Microphones are also called microphones, microphones, etc., in the circuit, commonly used symbols B or BM said. The microphone in the circuit of many types of microphones, according to the drive can be divided into electric microphone, condenser microphone, piezoelectric microphone, electromagnetic microphone, anti-static shoes, anti-static clothing carbon microphone and semiconductor microphone. According to the signal transmission can be divided into two kinds of wired and wireless microphones. According to the direction can be divided into heart type, Rui heart type, supercardioid, two-way (8-shaped) and no point (omnidirectional) and so on. According to the use can be divided into measuring microphone, vocal microphone, musical instrument microphone and recording microphone.

2, said the main parameters of the microphone performance

Sensitivity. This means that the microphone can produce the size of the audio signal voltage under the action of a certain external sound pressure. The unit usually uses mV / Pa (mV / Pa) or dB (0dB = 1000mV / Pa). General electret microphone sensitivity of more than 0.5 ~ 10mV / Pa or a 66 ~ a 40dB range. The higher the sensitivity of the microphone, the greater the amplitude of the audio signal output under the same size of sound.

Frequency response. This means that the sensitivity of the microphone changes with the sound frequency characteristics, commonly used curve to represent. Generally speaking, when the sound frequency exceeds the manufacturers given the upper and lower frequency, the sensitivity of the microphone will be significantly reduced. Electret microphone frequency response is generally flat, the general product frequency response is better (that is, the sensitivity is more balanced) in the range of 1001 {z ~ 10kHz, better quality microphone for the 40Hz ~ 15kHz, high-quality microphone up to 20Hz ~ 20kHz

Output impedance. This refers to the microphone at a certain frequency (1kHz) at the output of the AC impedance, the electret microphone through the internal field effect transistor impedance conversion, the output impedance is generally less than 3k. Q.

Inherent noise. This is the noise signal voltage output by the microphone when there is no external sound. The greater the inherent noise of the microphone, the greater the noise that is mixed in the output signal. General electret microphone inherent noise is very small, ∥ level voltage.

Directivity. It is also called the directionality, refers to the sensitivity of the microphone with the direction of the changes in the characteristics of changes. The directivity of the microphone is one of the unidirectional, bidirectional and omnidirectional. The sensitivity of the front side of the unidirectional microphone is obviously higher than that of the other direction. According to the shape of the characteristic curve, it can be subdivided into heart Type and ultra-directional type 3. The sensitivity of the bi-directional microphone in the front and rear directions is higher than the other directions. Omni-directional microphone for all the sound from all sides of the sound has the same sensitivity with the machine-mounted electret microphone is the most omnidirectional microphone.