Optocoupler is what powerful

The reason why the optocoupler transmit signals at the same time can effectively suppress spikes and a variety of noise interference on the channel signal to noise ratio greatly improved, mainly the following reasons:
(1) optical coupler input impedance is very small, only a few hundred ohms, and the impedance of the source of interference is large, typically 105 ~ 106Ω. According to the principle known partial pressure, even if the interference voltage amplitude is large, SPI lcds but is fed to the optocoupler input noise voltage will be very small, only a very weak current form, because there is not enough energy without emitting diode can thus be inhibited out.
(2) optocouplers between input circuit and output circuit is not electrically connected, there is no common ground; distributed capacitance between the minimum and the insulation resistance is so big, so the loop side of the various interference noise is difficult to pass Optocoupler fed to the other side, a total impedance coupling to avoid interference signal generation.
(3) optocouplers security can play a very good role, even when the external device fails, serial 16x2 lcd even when the input signal line short circuit, it will not damage the instrument. Because optocoupler input circuits and parts between the output circuit can withstand several thousand volts of high voltage.
(4) optocoupler fast response, the response time of only 10μs delay about the response speed for demanding applications.