What is AFT in weak electricity What does AFt mean in concrete

What is AFC (AFT) Circuit AFC (or AFT) is an abbreviation for "Automatic Frequency Control (or "Automatic Frequency Adjustment"). AFC circuits are widely used in electronic devices as important frequency stabilization or phase-locked circuits. This circuit has two functions:

The first is the tracking and locking of the received signal frequency; The second is phase tracking and locking. The local oscillator circuit of the medium and high frequency tuner of the color TV makes use of the frequency tracking characteristics of AFC, and the circuit structure is shown in Figure 1. The external high-frequency TV signal and the oscillation signal sent by the high-frequency head local oscillator circuit are mixed in the mixer to obtain a 38MHz image intermediate frequency signal, and then sent to the middle amplifier circuit.

If the frequency of the IF signal output by the mixer deviates from 38MHz, the discriminator will be able to detect the change and convert it to the corresponding DC voltage UAFC to fine-tune the local oscillator frequency. This DC voltage is the AFC voltage, which is used to ensure that the IF signal frequency output by the mixer is always 38MHz. It is worth mentioning that:

Now the high-frequency head of the new color TV has canceled the ABE terminal, and the ABL2 control voltage output by the discriminator will be sent to the AFC input terminal of the CPU. Then control the VT tuning voltage of the CPU output so that the frequency of the IF signal output by the high-frequency head is locked at 38MHz. In the circuit of the color TV line, the frequency and phase tracking characteristics of ABLE, are also used.

The structure of the AFC circuit is shown in Figure 2. If the line frequency output by the line oscillator is 1 5625 Hz, the line counterpath pulse fed back by the line output transformer and the line synchronization signal are compared in the phase detector, and the output phase control voltage will be zero. If the line frequency or phase output of the traveling oscillator is deviated, the counterpath pulse of the feedback phase detector is compared with the line synchronization signal of the input phase detector, and there will be an error voltage output.

This voltage, called the line contact voltage, is used to correct the frequency and phase of the line oscillator output. It should be added that,Now the line AFC function of color TV is generally completed inside the **IC (such asTDA8362),And there are two partsAFCL and ABL2。 The function of the internal loop of the **IC is to compare the frequency and phase of the line synchronization signal with the line oscillation signal, and can output an error current proportional to the phase difference to control the frequency and phase of the line oscillator.

The synchronized travel frequency signal is then added to the AFC2 loop, and the phase comparison is carried out with the reverse pulse signal of the person to ensure the center position of the image on the screen. [

Automatic Frequency Control, abbreviated as AFT

It refers to the calcium sulfoaluminate hydrate produced by the combination of cement hydration product C-A-H (calcium aluminate hydrate) and sulfate ions in concrete.

AFT is automatic frequency adjustment, some use AFC, is frequency automatic tracking, the meaning is similar, AFT is mostly used in high and medium amplification, and AFC is mostly used in line scan circuits. Sometimes it's also mixed.

Automatically scans the tracking circuit to adjust the TV picture to the best.

AGC, which is an automatic gain control, is used to balance the gain of the circuit signal. After the fault, the circuit will be self-excited or the signal will be weak.

AFT, which is an automatic frequency trimming, is used to adjust the IF signal. After a malfunction, the midrange will deviate and the picture will be unstable.

ANC, which is automatic noise cancellation, is used to eliminate noise in composite signals, and the noise figure of the image and accompanying sound will increase after a failure.

AFC is automatic frequency tracking, which is used to track the IF signal to make the IF more stable, and the IF will drift after the failure, and the picture will come and go.

ACC is automatic color control, the function is to stabilize the color signal, after the fault of the color will be thick and faint, or no color.

APC is automatic phase control, the function is to keep the signal in the correct phase, after the fault will be out of phase, the signal can not be effectively amplified.

Automatic Control Circuits in the Principles of Television Below are all the control circuits, Automatic Gain Control (AGC) circuits.

Automatic Level Control (ALC) circuitry.

Automatic Frequency Control (AFC) circuitry.

Automatic Noise Cancellation (ANC) circuitry.

Automatic Brightness Limiting (ABL) circuitry.

Automatic color saturation control (ACC) circuitry.

Automatic achromatic (ACK) circuitry.

Automatic Clarity Control (ARC) circuitry.

Automatic Power Control (APC) circuit for the laser head.

AFT is an automatic frequency control circuit. When the received TV signal has a frequency drift for some reason, the DC component of the ** signal detected inside the TV will change, and the DC component will be fed back to the oscillation circuit of the high-frequency receiving part through the internal feedback circuit to fine-tune the local oscillator frequency to compensate for the frequency drift of the external TV signal to achieve the best receiving effect.

Color TV sets have high requirements for the quality of the received signal, and a small frequency drift is likely to make the color decoding circuit unable to decode the color signal correctly, resulting in distortion or loss of color display. So the AFT circuit is set up to compensate for the frequency drift.

VCC DC power supply.

Feedback drain of the drain MOS tube.

The positive pole of the B+ battery.

keyi input key.

sync signal.

clamp position.

VCPAFC automatic frequency control.

ACL automatic frequency locking.

focusvs-out

hs-out

ACLDATA cable.

The CLK clock is stalled.

5V-V 5V power supply.

DDC DC power supply.

s rasd-data cable.

D-CLK digital clock signal.

vs-in input power ground.

hs-in

ABL-Auto Brightness Control Color Sync ACC-Auto Chromaticity Control.

ADJ-Regulator CRT, Picture Ture CRT AFC-Automatic Frequency Control.

AFT - Auto Frequency Trimmer DEF Yoke - Deflection Coil AGC - Auto Gain Control.

AM-AM-AM-Amplification-Amplification ARC-Auto Clarity Control.

audio-audio-bright-brightness-colour-chromaticity.

DL - Delay Drive, Stimulate Focus.

r resistance.

i Current ammeter.

u voltmeter voltage.