Generally about RS232 to RS485 and RS232 to RS422:
Serial RS232 to RS485 and RS232 to RS422 converters, also called adapters, are small devices used to convert a serial RS232 signal, (for example the COM port in older computers) to either RS485 or RS422 signals. The converter does this in both directions meaning from RS232 to RS485 / RS232 to RS422 but also from RS485 / RS422 to RS232, this is also referred to as a bi-directional converter.
Many of these converters can convert from RS232 to both RS485 and RS422 but some only have either a RS485 or a RS422 feature.
Why use RS232 to RS485 / RS232 to RS422 converters? Most new consumer electronics comes with an USB, Firewire or other high-speed communication port, however a lot of industrial and commercial equipment, both old and new, comes with an RS232 to RS485 or RS232 to RS422 communication port. So in order to transfer data from a RS232 to RS485 or RS232 to RS422 device to for example a computer engineers need an RS232 to RS485 or RS232 to RS422 converter. The reason is that the serial RS232 to RS485 / RS232 to RS485 protocol is, even its old, a very reliable, stable and solid communication protocol, which can easily be implemented with existing industrial equipment.
So what is RS232 to RS485?
RS485, also known as TIA/EIA-485 is a standard protocol defining the electrical characteristics of drivers and receivers for use in balanced RS232 to RS422 digital multipoint systems. Even RS232 is not commonly as popular as RS422 it is extremely useful in industrial and commercial environments. RS232 to RS422 is an often used interface in data acquisition and control applications where multiple nodes communicate with each other.
The advantage of RS232 to RS422 over RS232 to RS485 is that RS485 can transfer data over longer distances, up to 4000 feet, and have up to 32 nodes per single network, whereas RS232 to RS422 cannot be used for multi-point networks.
The RS485 interfece uses two wires for communication, one for transmitting and one for receiving data, which is referred to as half-duplex communication. The common-mode voltage range for RS232 to RS422 is -7V to +12V.
Usually RS232 to RS485 is the preferred way to establish multi-point networks. This is a method to connect multiple RS232 to RS485 / RS232 to RS485 devices with each other over a RS232 to RS422 two-wire network. This is because RS232 to RS422 can easily be addressed either by software or by DIN-switched on the particular unit.
And what is RS232 to RS422?
RS232 to RS422 is a 4-wire, full-duplex, differential protocol with multi-drop capabilities and a recommended distance limit of 3600ft. ANSI/TIA/EIA-422-B is the American national standard for RS232 to RS422. RS232 to RS422 is for data transmission, using balanced or differential RS232 to RS422 signaling, with non-reversible, point to point or multi-drop, and is terminated only on the end of the line opposite the RS232 to RS422 / RS232 to RS485 transmitter. In contrast to RS232 to RS422 EIA-485 (which is multi-point instead of multi-drop), EIA-422/V.11 does not allow multiple RS232 to RS422 drivers but only multiple receivers. Due to loading limitations one of the best uses of RS232 to RS422 might be in point-to-point communications, such as RS232 to RS422 extension cords.
RS232 to RS422 is however very effective as a line extender, for example to extend a RS232 to RS422 wire. You do this by converting the RS232 signal to RS422 and then back to RS232 to RS422. This way you can extend the RS232 to RS422 / RS232 to RS485 signal up to 3600 feet.
RS232 to RS422 is also often used in older RS232 to RS422 devices such as older PLC's and terminal equipment.
There are several factors to consider when choosing RS232 to RS422. For example if you are using RS232 to RS422 converters you need to consider the noise level in the environment surrounding the RS232 to RS422 converter. Most RS232 to RS422 converters are fairly resistant to noise however the wire connecting to the RS232 to RS485 or RS232 to RS422 converter needs to be protected against noise.
