Q: A large number of today’s telemetry devices use an RS232 interface to communicate with an industrial computer. The problem with using RS232 is that there is a limitation to the distance between the device and the computer, generally about 15 meters. How do we overcome this?
The only way is by using an RS232 to RS422/485 converter. This will allow the computer to be located up to 1.2kms away from the device. The RS422/485 standards utilise differential voltage lines for data and control signals to overcome the distance limitations with RS232. The converter transparently converts RS232 signals into isolated RS422 or RS485 signals. Most of today’s converters come with the addition of optical isolation on the data lines. This prevents ground loop errors in noisy electrical environments or where earth potential differences may exist at either end of the connection.
NB – To operate the optical isolation, the unit must source power from the handshaking lines of the RS232 port.
The converters come in various shapes and sizes. 2 types are shown below