3.1 on the hardware circuit part of the anti-interference measures
3.1.1 on the AC voltage interference suppression
(1) the use of switching power supply for the performance of the test system power supply because of the switching power supply and the general DC power compared to the anti-interference ability to occupy the absolute advantage. But in the use of the switching power supply to pay attention to the use of good performance for the microcomputer control test machine system power supply, otherwise not only can not suppress interference will also produce interference.
(2) the use of isolation transformer
Because of the ordinary transformer on the interference without any inhibition, and isolation transformer installation of the secondary layer of shielding between the isolation layer can reduce the distribution capacitance, thus improving the test machine system **** mode interference ability.
(3) Configuration decoupling capacitance
In the power input across the 10 ~ 100μF electrolytic capacitors, in principle, each IC chip power line and ground line indirectly a 0.01μF ceramic capacitor as decoupling capacitance.
(4) in the AC power supply secondary transient voltage suppressor connected to a high energy shock, it can be 10-12 seconds at the speed of the order of magnitude, between the poles of the high impedance into a low impedance, absorbing thousands of kilowatts of surge power, so that the voltage between the poles clamped to a predetermined value, thus effectively protecting the components of the electronic circuits from all kinds of surge impulse damage. In the AC power supply secondary and connect a TVS tube, can play a role in protecting the power supply secondary circuit from the impact of pulse interference.
3.1.2 Signal channel interference suppression
(1) material testing machine input channel using photocoupling isolation measures photocoupler input impedance is very small, while the interference source of the internal resistance is very large, so can be sub-pressurized to the photocoupler input interference is greatly weakened. But the general photocoupler linearity is very poor, can only be used to isolate the digital input and output channels.
(2) material testing machine input channel and connect TVS tube to protect the input line behind the precision components from a variety of surge pulse damage.
(3) material testing machine input channel using isolation amplifier with isolation amplifier to isolate the analog input and output channels, not only can suppress the interference, but also with a very good linearity.
(4) material testing machine on the suppression of reverse electromotive force there are two ways to inhibit: one is in the AC coil with coil devices (such as relays, motors) at both ends of the parallel RC circuit; the second is in the DC coil at both ends of the parallel connection of a resistor, diode series circuit, but also at the same time in the RC or RD circuit ends of the parallel connection of a varistor or TVS tube.
3.1.3 test machine system grounding anti-interference measures
(1) test machine input signal circuit virtual ground technology
Front being a large circuit performance is directly determined by the analog front-end and to the entire system performance, and the front part of the introduction of interference signals is very difficult to completely eliminate. In order to minimize similar interference, the signal loop virtual ground technology is used, i.e., the signal reference terminal and the ground loop of the analog circuit is connected to the zero-current connection between the signal loop and the analog circuit to ensure that the signal loop and the analog loop to achieve quasi-isolation (shown in Figure 1).
(2) microcomputer control test system using multi-level floating technology
Multi-level floating technology is mainly used to solve the problem of grounding circuit current on the normal operation of the system to bring the impact. In the microcomputer control system, due to a variety of different working ground may introduce the corresponding interference signal, and the interference signal superimposed back to the signal loop, which affects the final collection of data. In order to ensure the effectiveness of the test data and the stability of the system, the use of multi-level floating anti-jamming technology to maximize the ground current to cut off a variety of coupling paths, in order to fully realize all the interfering signals shielding, isolation in the signal loop outside the anti-jamming goal. For example, the microcomputer chassis ground and AC ground through the DC-DC converter for isolation; analog ground and digital ground through the photocoupler for isolation, analog ground and signal ground through the signal loop virtual ground technology for isolation and so on. Through such a level of isolation measures to make the signal circuit multi-level floating in the system ground (chassis ground) above, so as to achieve the protection of the signal circuit, protection and purification of the input signal purpose.
(3) The metal shielding of the main machine and external equipment is directly connected to the earth.
(4) The use of grounded choke coil can prevent current and high-frequency current interference.
3.1.4 Space radiation interference suppression
Space radiation interference is mainly space electromagnetic wave interference. According to Xianjie net editorial understanding of the material testing machine more digital instrumentation, digital instrumentation due to high precision, compared with pointer type instrumentation by the impact of interference is greater. Inhibit the interference of space electromagnetic radiation is electric shielding and magnetic shielding. The use of electric shielding approach can be placed in the microcomputer-controlled testing machine cabinet in a closed metal enclosure, the enclosure directly to the earth. Magnetic shielding approach is to use two or three layers of magnetic shielding; with initial permeability but not saturated silicon steel sheet to do the outer shielding, the use of high initial permeability but easily saturated Po Mo alloy to do the inner shielding, you can give full play to the performance of the material and get a better shielding effect.
3.2 Software anti-interference measures
3.2.1 Digital Filtering
Input channel of the hardware does not completely eliminate the interference in the signal data is used before the use of digital filtering technology can achieve better results.
3.2.2 Select the appropriate sampling time
For the integrated analog-to-digital conversion circuit, the sampling time should be taken as an integer multiple of the frequency period, which will help to suppress the frequency interference.
This will help to suppress industrial frequency interference.