Sensors and instrumentation anti-interference methods are there?

For sensors and instrumentation anti-interference methods to sum up the following three points, you can reference! Sensor instrumentation anti-interference one: the anti-jamming design of the power supply system of sensor instruments work normally is the most serious harm grid peak pulse interference, the interference peak electricity equipment are: electric welding machine, large motor, controlled machine, relay contactor, with inflatable lighting ballasts, even soldering iron, etc. Peak interference available hardware, software, combining with the method to suppress. ( 1) Hardware circuit to suppress interference of peak common means there are three main types: (1) in series with the ac power input instrument according to the spectrum interference controller designed by the principle of balanced, the peak voltage of power distribution on different frequency bands, and decreases its destructive; (2) in the ac power input and super instrument isolation transformer, using the principle of ferromagnetic resonance inhibit spikes; (3) in parallel with the instrument of the ac power input pressure sensitive resistance, using the spike pulse arrives from resistance decrease in order to reduce the instrument power supply voltage, so as to weaken the influence of interference. ( 2) Peak interference suppression with software method for periodic interference, programming may be used for filtering, time also is to use the program control thyristor conduction instantaneous sampling, effectively eliminate the interference. ( 3) Combined with hardware and software watchdog technology inhibit the effects of peak pulse software: before the timer timing to CPU accesses a timer, timer to start timing, program is running normally, the timer will not produce overflow pulse, watchdog won't work. Once peak interference appeared 'fly program, the CPU is not in time to visit before the timer, thus timing signal will appear, so as to cause the system reset interrupt, ensure intelligent instrument back to the normal process. ( 4) Implements the power groups, such as: separate actuating motor drive power and control power, to prevent interference between devices. ( 5) The noise filter can effectively inhibit ac servo drive interference with other equipment. The measures of the above several kinds of interference phenomenon can be effectively suppressed. ( 6) Main transformer in considering the high frequency isolation transformer noise through the primary and secondary coil is not by the mutual inductance coupling, the primary and secondary parasitic capacitance coupling, but by so the primary and secondary between the isolation transformer shield isolation, reduce the distributed capacitance, in order to improve the common-mode interference resistance ability. ( 7) With high anti-interference performance of power, such as spectrum equilibrium method is used to design the high anti-interference power supply. The power supply resistance to random disturbance was so effective that it can bring a high peak voltage disturbance pulse into peak (low voltage The peak voltage is less than the TTL level) Voltage, but the interference pulse energy is constant, which can improve the anti-interference ability of sensors, instruments and meters. Sensor instrumentation anti-interference and signal transmission channel anti-interference design ( 1) Photoelectric coupling isolation measures in the process of long distance transmission, adopting photoelectric coupler, can control systems with input channel, output channel and servo drives the connection between the input and output channels to cut off the circuit. If you don't adopt photoelectric isolation in the circuit, external rush disturbance signal will enter the system or directly into the servo drive device, the first kind of interference phenomenon. Photoelectric coupling's main advantage is can effectively inhibit the spikes and various noise interference, the signal transmission process of signal-to-noise ratio was improved greatly. Interference noise, although there is a large voltage range, but the energy is very small, can only form a weak current, and the photoelectric coupler input part of light emitting diode is work under current condition, general guide electric current of 10 ma ~ 15 ma, so even if there is a big range of interference, the interference will be unable to provide enough current and suppressed. ( 2) Long twisted-pair shielded wire transmission signal in the process of transmission will be affected by electric field, magnetic field and ground impedance interference factors, such as using ground shielded wire can reduce the interference of electric field. Twisted-pair compared with coaxial cable, although the low frequency band, but wave impedance is high, the common mode noise resistance is strong, can make the electromagnetic interference of each little link cancel each other out. In addition, in the process of long distance transmission, generally USES the differential signal transmission, can improve the anti-jamming ability. Using twisted-pair long shielded wire transmission can effectively suppress interference phenomena mentioned above (in the 2) 、( 3) 、( 4) The generation of interference. Sensor instrumentation anti-interference three, elimination of local produce error in low level measurements, used in the signal path, Or form) Materials strict attention must be given, the solder in the simple circuit, wire and terminal can have real thermoelectric potential. Because they often come in pairs, so try to keep these pairs of thermocouple are effective measures in the same temperature, therefore generally with heat shield, radiator arranged along the isotherm. 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