Sensor, change send implement design of interference rejection ability
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source:AYOR CNC Machining
One, introductive sensor changes send implement application is very wide, it is no matter build in industry, agriculture, national defence, still consider to wait for a domain in enterprise of daily life, education and science, see the figure of imitate sensor everywhere. But in design and be being used in imitate sensor, how one makes its measure precision to obtain top issue. And disturb what affecting sensor all the time numerously to measure precision, be like: Spot big bad news can equipment is much, especially high-power sensibility is opened ladenly stop to often can make electrified wire netting produces hundreds of hot season even the pointed pulse interference of thousands of bend over; Industrial electrified wire netting is owed press or press too (voltage of power supply of ironworks of experience county steel fluctuates in 160V ～ 310V) , often achieve the 35 ％ left and right sides of rated voltage, this kind of abominable power supply is as long as a few minutes sometimes, a few hours, even a few days; All sorts of line colligation are together or take same root multicore cable, signal can be disturbed, disturb in the conduit that line and communication power line go to grow together especially blame very; Multichannel switch or maintain implement performance is bad, also can cause the harass of passageway signal; Space the change of geomagnetic even field also can disturb condition of all sorts of electromagnetism, weather, thunder the regular job of sensor; In addition, the change of spot temperature, humidity may cause circuit parameter to produce change, the action of salt of caustic gas, soda acid, field sand blown by wind, drench, even the dependability that rat bites the metropolis such as bug eat by moth to affect sensor. What imitate sensor outputs is general it is small signal, put in small signal enlarge, processing, plastics and interference rejection problem, the uniform standard signal that magnifies the faint signal of sensor accurately place needs namely (be like 1VDC ～ 5VDC or 4mADC ～ 20mADC) , reach the technical target of a need. The certain problem that this asks to design fabricant to must notice to did not express on graph of imitate sensor circuit, namely interference rejection problem. Make clear way of the interference source of Hunan imitate sensor and interference effect only, the design gives the circuit that removes interference or the measure that prevent interference, ability achieves the groove that uses imitate sensor. 2, the interference that sort of interference source, interference and interference phenomenon sensor and instrument appearance run place to get in the spot is varied, particular case is particular analysis, taking different step to different interference is the principle of interference rejection. Comfortable sex of the strategy of this kind of flexible for emergency use and general is contradictory undoubtedly, settlement way is to use modular method, besides main component part, be aimed at different moving situation, the instrument can assemble different options with effectively interference rejection, raise dependability. Before the option that discussing circuit element further, circuit and systematic application, be necessary to analyse the interference source that affects imitate sensor precision and interference sort. 1, basically disturb source (1) because there is parasitism capacitance between a circuit or two component,electrostatic induction static electric induction is, make the charge on a spur track conveys to go up to another spur track through parasitism capacitance, because this calls capacitance sex coupling again. (2) when electromagnetism induction should have mutual inductance to exist between two circuit, the change of the electric current in a circuit can arrive through magnetic field coupling another circuit, this one phenomenon calls electromagnetism reaction. For example lead of parallel of the leakage magnetism of transformer and coil, electrify. (3) leakage current induction because column of the component bracket of electronic circuitry interior, wiring, printed circuit board, the insulation such as capacitance interior medium or crust is undesirable, especially the applied environment humidity of sensor is bigger, the insulation resistance of dielectric drops, bring about residual current to increase to be able to cause interference. Flow into the input that measures circuit when leakage current especially when class, its effect is particularly serious. (4) radio frequency disturbs basically be large power plant to start, the interference of layoff and interference of Gao Cixie wave. The interference that is like system of commutate of silicon controlled rectifier. (5) supervisory system of safe production of other interference spot besides sufferring above easily to disturb, because systematic work environment is poorer, be reached chemical interference to wait easily still by mechanical interference, hot interference. 2, the phyletic of interference (1) constant model disturbs constant model is to point to those who disturb signal to invade be in going there and back is consistent on 2 lines. Origin of constant model interference is commonly all round stronger hand in change magnetic field, make the instrument suffers all round hand in change to magnetic field is affected and produce communication electromotive force to form interference, this kind of interference gets rid of harder. (2) in all the model is disturbed in all modular interference is to point to interference signal to had shed one part each on 2 lines, it is communal loop with the ground, and signal electric current is in only go back and forth between 2 circuitry midstream to pass. In all the source that the model violates is equipment commonly itself of voltage of right leakage of electricity, ground, circuitry has right interference to wait. As a result of the lopsided condition of circuit, in all modular interference can change Cheng Changmo to disturb, got rid of harder. (3) the interference when the interference when growing is long is to point to long-standing interference, the characteristic of this kind of interference is interference voltage is long-standing and change is not big, use measuring instrument to be measured very easily, if power supply cord or vicinity move the electromagnetism of line of force,interference is successive communication interference of 50Hz labour frequency. (4) when accident instantaneous disturbs accident instantaneous interference to basically be operated in electric equipment, happen, if add up to brake or cent brake to wait, also be in sometimes accompany thunder happening or generation of instant of radio equipment work. Interference can divide roughly for 3 respects: (A) local generation (the thermocouple that does not need namely) ; (B) the coupling of subsystem interior (namely the method problem) of ground wire; (C) exterior generation (the interference of frequency of Bp power source) . 3, interference phenomenon is in application, regular meeting encounters phenomenon of the following kinds of main interference: (1) when bristle with anger makes, electric machinery does not have regular roll; (2) signal is equal to zero hour, the number shows watch numerical value frisks; (3) when sensor works, the signal that its output value and correspondence of actual parameter place is worth not be identical, and error value is random, mobbish; (4) below the situation that stabilizes when the parameter that be measured, the poor value of the numerical value that sensor outputs and the signal numerical value with corresponding place of the parameter that be measured is one stability or the value that show periodic change; (5) the equipment of common and as same as communication servo power source (wait like monitor) the job is abnormal. Interference enters the channel that decides position control system to basically have two kinds: Signal transmits interference between channels, interference inputs passageway, output passageway to enter through the signal that connects with the system; Interference of power supply system. Signal transmission passageway is to control system or driver to receive feedback signal and the channel that issue control signal, because pulse is in,delay time, distortion, attenuation and interference between channels can appear on transmission line, it is so in transmission process, long term interference is main factor. Any power source and transmission network are put in internal resistance, be the noise interference that these internal resistance just caused power supply, if do not have internal resistance, no matter why be planted,noise can be absorbed by power source short circuit, any interference voltage also won't be built in circuit; In addition, communicating servo driver itself also is stronger interference source, it can undertake disturbing to other equipment through power source. 3, the measure of interference rejection 1, the interference rejection design of power supply system is normal to appearance of sensor, instrument working harm is the most serious is interference of pulse of aiguille of electrified wire netting, produce the equipment using phone of aiguille interference to have: Electric welder, big electric machinery, can control contactor of report of machine, afterwards, area of ballast aerate floodlight, even electric iron. Aiguille disturbs the idea that usable hardware, software combines to restrain. (1) affect commonly used method to basically have 3 kinds with what hardware circuitry restrains aiguille to disturb: ① inputs end to string together the interference controller that by spectrum balanced principle designs in instrument alternating current source, the energy that concentrates aiguille voltage allocates different frequency paragraph on, thereby abate its are ruinous; ② inputs end to add super segregation transformer in instrument alternating current source, use ferromagnetic resonance principle to restrain aiguille pulse; ③ carries paralell connection to press in the input of instrument alternating current source quick resistor, the resistance when using aiguille pulse to come reduces the tension that shares from power source with reducing an instrument, weaken the influence of interference thereby. (2) use software method to restrain aiguille to disturb to periodic interference, can use process designing to have time filter wave, guide with programme controll silicon controlled rectifier namely an instant not sampling, remove interference effectively thereby. (3) the watchdog that uses band of hard, software (Watchdog) the influence software that the technology controls aiguille pulse: Before timer times, CPU visits timer, make timer new begin to time, normal procedure moves, this timer won't arise spill over pulse, watchdog also won't act well. Once aiguille interference appeared " flying program " , criterion CPU won't visit timer before timing, consequently time signal can appear, cause systematic restoration to interrupt thereby, make sure intelligent apparatus returns normal procedure to come up. (4) execute power source in group power supply, for example: The drive power source that will carry out electric machinery and control power source are apart, in order to prevent the interference between equipment. (5) use noise filter to restrain the interference of communication servo driver to other equipment effectively. This measure disturbs a phenomenon a few kinds to be restrained effectively to above. (6) using segregation transformer to consider high frequency noise passes transformer basically is not to lean first, the mutual inductance coupling of secondary coil, lean however first, of coupling of sub parasitism capacitance, keep apart transformer accordingly first, sub between all keep apart with screen layer, reduce its to distributing capacitance, in order to increase resistance in all the model disturbs ability. (7) the power source that uses property of tall interference rejection, if use spectrum,the Gao Kang of balanced law design violates power source. Resistance of this kind of power source is disturbed randomly very effective, it can Gao Jianfeng disturb voltage pulse is changed into low voltage peak value (voltage peak value is less than TTL n) voltage, but the energy that disturbs pulse is changeless, can increase the interference rejection capacity of appearance of sensor, instrument thereby. CNC Milling