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How to eliminate the incremental encoder signal interference?

by:HENGXIANG     2020-11-26
How to eliminate the incremental encoder signal interference? Article source: release time: 2019/04/10 hits: have you ever met a interference problem? Automation control, interference often talk about the problem, eliminate interference of stories also has a variety of, have said use twisted-pair shielded cable, has said how well grounded, I heard the most exaggerated story is in the ground to sprinkle the salt of the pile, I often online publicity absolute encoder, because have a net friend meet incremental encoder signal interference problems can find me. In the end I just asked him, what with encoder ( Model and signal) After, gave him an advice: throw out! Change the selection of again. Interfere with the first is the problem in the selection of the encoder, don't just superstition is imported, and selection of the encoder is the first step in the right, while the iron is hot to their own hard. How to eliminate the incremental encoder signal interference? First, turn the motor to use oscilloscope to check the high and low level of encoder pulse waveform and the waveform, both to look at the amplitude of high level, also want to despise level amplitude, should be 'day' and 'ground'. Not 'day' and 'land', will see if encoder signal interface impedance matching. In addition, I want to watch pulse encoder signal along, pulse along the steep, otherwise is also a problem. Second, use the trace record to see inside the encoder signal, if there is something wrong with the waveform. If the noise, Waveform of the burr) Seriously, that is the signal interference. Check these, we need to set the inverter control mode to form a encoder feedback of V/F control and vector control. That is the function block encoder feedback. Third, shielding technology, select all metal without screws closed shell shielding encoder 1. Electrostatic shielding: electrostatic shielding is to use copper or aluminum for good performance of conductive metal materials into a closed metal shell, and connected to the ground, put to mask encoder circuit in which the electric field makes the external interference of electric field does not affect the internal circuit. Encoder, in turn, the internal circuit of power line cannot escape to affect the external circuit. Electrostatic shielding can not only prevent electrostatic interference, also can prevent the interference of alternating electric field, so many instruments of shell made of conductive material and grounded. As a metal shield shell, should be the whole package shield, and try to do not have sharp corners and different metal screws, metal conductor Angle by 'cutting edge effect' to become a electric field distortion interfere with the absorption of the antenna. Similarly, the screw because the metal characteristics of different material is different, as there will be the tip of the boundary effect and introduce the interference. Encoder housing edges smooth without screws packaging technology and application, guaranteeing the best effect of metal shielding layer. 2. Low-frequency magnetic shielding, low frequency magnetic shield is used to isolate low-frequency magnetic field and a fixed magnetic field coupling interference of effective measures. All around by current conductor or coil magnetic field, magnetic field exists objectively, they may cause magnetic field coupling to the testing instrument signal lines or equipment. In order to prevent interference magnetic field coupling, high permeability material must be used as a shield, so that the low frequency interference magnetic field lines from the magnetic resistance is very small magnetic shielding layer, make the low-frequency magnetic shielding layer of internal circuit from the effects of low frequency magnetic field coupling interference. Instrument of iron shell, for example, have the effect of low-frequency magnetic shielding. If further ground to the electrostatic shielding effect at the same time. Metal iron shell, or larger encoder metal aluminum shell, external magnetic interference sources may be far away from the internal power supply, sensor and MCU, the change of the external magnetic field energy absorption, all metal shielding layer can absorb low-frequency magnetic oscillation due to the energy. The interference of magnetic field weakening magnetic sources. 3. Electromagnetic shielding, electromagnetic shielding is also the good conductive metal materials different shapes, such as shield, shielding box in which will be surrounded by a protection circuit. Its interference shielding object is not the electric field, but the high frequency ( More than 40 KHZ) A magnetic field. Interference sources produced by high frequency magnetic field in electromagnetic shielding layer of conductive good, on the outside surface of the same frequency eddy current sensor, which consumes energy of high frequency interference, so that the electromagnetic shielding layer inside the circuit from the effects of high frequency interference magnetic field. 4, reduce the number of signal transmission terminal Angle thrum, a cable directly to the receiver as far as possible. Receive cable threads in the middle of the signal transmission is a exposure to interfere with the absorption unit 'antenna', especially the thread and the metal Angle seems to be stretched out to the antenna, the connecting cables should be no exposed outside the thrum of the skip, do rounding processing, should try to avoid in the signal transmission thread with sharp corners. Incremental encoder signal choice, should choose to have the output signal of the same word, should choose A + A - B + B - Z+Z- 6 channel signal output type of incremental encoder, among them, the push-pull HTL - including the believe number 6 channels G6( A/A- ,B/B- ,Z/Z- ) , on the one hand, its 9 - 30 v power advantages and wide polarity, short circuit protection is not easy to damage, on the other hand, due to the interference sources for encoder is letter good interference effect, interference can be offset in the encoder receiving equipment, this kind of incremental encoder signals transmission can achieve without interference, transfer is farther ( Special cable 200 m, according to the cable with the situation) , this kind of signal is given priority to with European transducer interface, should first consider used in metallurgy, port machinery.
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