signal isolator
A signal isolator is used to isolate the inputsingle laneOr dual current or voltage signals, transmitting and outputting isolated single or dual linear current or voltage signals, and improving the electrical isolation performance between input, output, and power supply. Signals may encounter various interferences during transmission, and it is particularly important to use signal isolators to ensure signal stability.
working principle
Firstly, the signals received by the PLC are modulated and transformed through semiconductor devices, and thenlight sensingOr the magnetic sensing device is isolated and converted, and then demodulated and transformed back to the original signal before isolation or different signals, while the isolated signal is subjected topower supplyPerform isolation processing to ensure independence between the transformed signal, power supply, and ground.
Anti disturbance measures
Anti interference design of power supply system
The serious hazard to the normal operation of sensors and instruments is the peak pulse interference of the power grid. The electrical equipment that generates peak interference includes welding machines, large motors, controllable machines, relay contactors, inflatable lighting fixtures with ballasts, and so on. Peak interference can be suppressed using hardware, software, and/or a combination of hardware and software.
There are three common methods to suppress the impact of peak interference using hardware circuits:
Connect an interference controller designed according to the principle of spectrum equalization in series with the input end of the instrument's AC power supply, and distribute the concentrated energy of the peak voltage to different frequency bands, thereby reducing its destructive power;
Add a super isolation transformer to the input end of the instrument's AC power supply and use the principle of ferromagnetic resonance to suppress spike pulses;
Connect a varistor in parallel at the input of the instrument's AC power supply, and use the decrease in resistance value when the peak pulse arrives to reduce the voltage that the instrument receives from the power supply, thereby weakening the impact of interference.
Using software methods to suppress peak interference
For periodic interference, programming can be used for time filtering, which means controlling the thyristor to conduct without sampling at the moment of conduction, effectively eliminating interference.
Using a combination of hardware and software watchdog technology to suppress the impact of spike pulses
Software: Before the timer expires, the CPU accesses the timer once to restart the timer. The program runs normally, and the timer will not generate overflow pulses, so the watchdog will not work. Once a "flying program" occurs due to peak interference, the CPU will not access the timer before the scheduled time, resulting in a timing signal that triggers a system reset interrupt to ensure that the smart instrument returns to its normal program.
Implement power supply grouping, for example: separate the driving power supply of the motor from the control power supply to prevent interference between devices.
The use of noise filters can also effectively suppress the interference of AC servo drives on other devices.This measure can effectively suppress the above-mentioned interference phenomena.
Technical Features
The signal isolator adopts advanced digital technology and has excellent performance in suppressing high and low frequency interference signals. Even in high-power variable frequency control systems, it can still be reliably applied. Internally, it adopts many advanced technologies such as digital calibration, zero free and full-scale potentiometers, automatic dynamic zero calibration, and temperature drift automatic compensation. The application of this series of technologies ensures the stability and reliability of the product scientifically. The above technologies are at the international advanced level.
Signal isolators can be used in conjunction with unit combination instruments, DCS, PLC and other systems, and are widely used in major projects in industries such as oil fields, petrochemicals, manufacturing, power, metallurgy, etc.
Related models: LDG8041 LDG8043 LDG8044 LDG8045 LDG8042
