The force detection components currently used on testing machines are basically load sensors or pressure sensors, and analog signal output extensometers. These two types of sensors and extensometers are analog small signal output types, and signal amplification must be performed during use.
As we all know, there are various electromagnetic interference signals in our environment. This interference signal will be coupled into the measurement signal through many different channels and amplified together. As a result, the useful signal will be drowned by the interference signal.
In order to extract useful signals from interference signals, a low-pass filter is generally installed in the amplifier according to the characteristics of the material testing machine. Properly setting the cutoff frequency of the low-pass filter and limiting the frequency band of the amplifier to an appropriate range can greatly improve the measurement and control performance of the testing machine.
However, in reality, people often regard the stable display of data as very important, but ignore the authenticity of the data, and set the cutoff frequency of the filter very low. Of course, the benefit is that the speed is accelerated and it is very stable. In this way, while fully filtering out interference signals, useful signals are often filtered out as well. In daily life, the data of our common electronic scales is very stable. One of the reasons is that its frequency band is very narrow and interference signals can basically not pass through. The reason for this design is that the electronic scale weighs a steady-state signal and is not concerned with the transition process of weighing, while the material testing machine measures a dynamic signal, and its spectrum is very wide. If the frequency band is too narrow, the high Frequency signals will be attenuated or filtered,
Of course, I agree with this view. From an economic and practical point of view, I personally think that dial-type testing machines are actually very good.
The following is the concept of bandwidth, for reference only!
Bandwidth is a critical concept in many applications. For example, in radio communications, bandwidth is the range of frequencies occupied by a modulated carrier, whereas in optics bandwidth is the width of a single spectral line or the entire spectrum.
There are different precise definitions for different application areas. For example, one definition of bandwidth is the frequency range beyond which the frequency function is zero. This corresponds to the mathematical concept of a function, such as the “length” of all values for which the function is not zero.
Other definitions may be less strict and discard signal frequencies for which the frequency function is “very small”. Small may mean that its value is below 3 dB of the maximum value, which is less than half of the maximum value; it may also mean that it is less than a certain absolute value. Since there are various definitions of the width of a function, there are also various definitions of bandwidth, which are used in different systems.
According to the Shannon-Hartley theorem (en:Shannon-Hartley theorem), the data rate of reliable communication is directly proportional to the frequency range of the signal used for communication. In this article, the term bandwidth is sometimes used to refer to the data rate, sometimes to the frequency range of the communication system, and sometimes to both concepts at the same time.
[edit] Simulation systems
For analog signals that can be viewed mathematically as a function of time, the bandwidth is the frequency range in Hertz over which the Fourier transform of the signal is not zero. This definition can also be loosely defined as the frequency range in which the Fourier transform power of the signal is above a certain threshold, for example, within 3 dB of the maximum value. Signal bandwidth is a measure of how quickly a signal fluctuates over time, such that the larger the bandwidth, the faster the signal changes. The above is a description of signal bandwidth, bandwidth can also be used for systems. When expressing system bandwidth, system bandwidth is the abbreviation of system transfer function bandwidth.
For example, the 3dB bandwidth of a function is represented on the graph as f2 − f1, but other bandwidth definitions will give different results. A commonly used quantity is fractional bandwidth, which is the bandwidth divided by the center frequency of the device. For example, a device with a bandwidth of 2MHz and a center frequency of 10MHz would have a fractional bandwidth of 2/10 or expressed as 20%.
The fact that real baseband systems have both negative and positive frequencies can make bandwidth confusing, because sometimes bandwidth is used to represent just the positive half, for example we occasionally see the representation B = 2W, where B is The total bandwidth, W, is the positive bandwidth. If you need to design a low-pass filter for this signal, then the cutoff frequency must at least ensure that W is not affected.
Electronic filter bandwidth is the portion of the frequency where the response is within 3dB of the peak center frequency response.
In signal processing and control theory, bandwidth is the frequency at which the gain of a closed-loop system decreases to −3 dB.
In basic circuit theory, the bandwidth of a bandpass and bandstop filter represents the distance in the frequency domain between two frequencies where the signal strength is maximum.
In photonics, bandwidth has different meanings:
- The bandwidth of the output of some light sources, such as ASE sources or lasers; the bandwidth of ultrashort light pulses can be very wide
- The width of the frequency range that some components, such as fiber optics, can transmit
- Gain bandwidth of optical amplifier
- Range of other phenomena (e.g. reflection, phase matching of nonlinear processes, or resonance)
- Maximum modulation frequency or modulation frequency range of the optical modulator
- The frequency range in which some measuring instruments (e.g. power meters) can operate
- The data rate that the optical communication system can achieve (e.g. Gbit/s)
