RS485 Surge Protectors
RS485 Surge Protectors are ideal for protecting RS-422 and RS-485 lines as well as providing protection for sensors, control lines. RS485 Surge Protectors are essentially high-speed, self-resetting switches designed to balance communication lines with chassis (earth) ground in the event lines become over-energized.
RS485 serial port lines are quite prone to be damaged by overvoltages. The damaged to computer serial ports have become more and more expensive to replace because of higher intergaration: usually you have to buy new motherboard if one serial port in it gets broken.
So it is wise to use some extra protection in situations where overvoltages surges are quite propabe and repairing gets expensive. For examples of this type of situations are long serial port lines side the building and situation where the computer is connected to ungrounded outlet or the electricity distribution wiring is is not well organized.
Protecting RS-485 serial port against overvoltages usually quite easy with RS485 Surge Protectors. The standard says that the signal can be voltage between +25 and -25 volts, so anything outside this range is not allowed. Typical RS-485C receiver chips can handle well voltages up to +/-30V. So an overvoltage protection which cuts out everyhing above 25V and acts fast is the solution. Suitable components for this are varistors (VDR), zener diodes and other fast semiconductor based overvoltage protection devices.