The commonly used amplification and adjustment circuit can generally be divided into three or four main parts: a zero-adjustment circuit, a signal amplification and gain circuit, a filtering circuit, and a V/I conversion circuit.

Zeroing Circuit: The purpose of the zeroing circuit is to adjust the zero bias of the sensor signal or to modify the zero-point offset as required by the subsequent stages. 48 Friction Material Testing Machine and Testing Technology: If a certain sensor or transmitter outputs a signal in the range of 1–5 V, while the A/D card in the computer control system has an input range of 0–5 V, theoretically...
The 1–5V signal can be used directly, but its accuracy will be reduced by 20%. If you use zeroing followed by a 1.25x amplification to convert the signal into a 0–5V range, you can avoid any loss in accuracy.

Amplification Circuit: The purpose of an amplification circuit is to amplify weak signals into signals that are compatible with the subsequent stage, or to adjust the signal strength so that it matches the requirements of the downstream circuit. For example, consider the signal from a strain-type tension-compression sensor. Typically, the maximum strain output of a tension-compression sensor is...
Millivolt-level voltage—or, through high-magnification amplification, it can be converted into volt-level voltage required by the subsequent stage, and so on.

Filtering and V/I Conversion Circuit: Typically, hardware filtering uses capacitors in conjunction with other components to eliminate extraneous signals and external interference, thereby ensuring that the desired signal has excellent quality. The V/I conversion circuit—also known as the voltage-to-current conversion circuit—is primarily designed for long-distance signal transmission, reducing signal loss and enhancing anti-interference capability. For example, suppose a 0–5V signal is transmitted over a one-kilometer-long wire; by the time it reaches the destination, the signal may have been severely attenuated. However, if the same signal is converted into a 0–20mA current signal and transmitted using a constant-current source, the signal will not suffer any loss, and the introduced transmission interference will also be minimal.

Amplifier Circuit Adjustment and System Calibration: The basic principles underlying the two amplifier circuit adjustment and calibration methods are identical, as illustrated in several configurations shown in Figure 4G26.

Generally, servo amplifier circuits typically employ either a proportional controller (P) or a proportional-integral controller (I). The role of the proportional controller is to accelerate the response speed, while the integral action serves to reduce steady-state error. Proportional control is a "with-error" regulation, whereas the proportional-integral controller achieves "zero-error" regulation. In essence, proportional control is simply an amplification process: it amplifies the difference between the reference signal and the feedback signal to drive the actuator. On the other hand, the integral action integrates the difference between the reference and feedback signals; as long as there is any deviation, the integral will keep accumulating, continuously driving the actuator until the error is eliminated. The adjustment of the servo circuit directly determines the quality of the control performance. If the proportional gain is too small, the response will be too slow; if it’s too large, oscillations are likely to occur. Similarly, improper coordination between the integral and proportional actions can also lead to oscillations or excessive steady-state error. The specific adjustment methods will be discussed in subsequent chapters.