In this day and age, why use serial communicationsCONTROL ENGINEERING China版权所有, such as RS-232, RS-422, and RS-485? Digital industrial networks, fieldbuseswww.cechina.cn, device- and sensor- level networks (also USB) all support many vendors’ products and can offer advanced features for configuration and diagnostics. So why use serial? Answers are low cost, simplicity, and familiarity. Industrial serial communicationsCONTROL ENGINEERING China版权所有, largely RS-232, RS-422, and RS-485, are still included on many products and machines because they provide simple, bi

　　Hybrid communication modules, such as the Moor Industries International microNCS, include serial (Modbus-RTU and RS-485), EthernetCONTROL ENGINEERING China版权所有, and I/O connections.
　　Serial communication， still exists, says Jim Toepper, product manager for the connectivity group of Moxa Americas, because:
　　It remains an easy and inexpensive way to communicate with devices. Most vendors will offer a serial-only version as an entry-level product, offering an Ethernet-enabled version as a higher end offering;
　　If a product has been in production for many years and is proven, it could be cost- prohibitive for a device manufacturer to redesign and recertify an Ethernet (or other network-enabled) version of the same product. While Ethernet components themselves are not that much more expensive than serial componentsCONTROL ENGINEERING China版权所有, implementation and design of Ethernet can be costly. “In some cases it is actually less expensive to buy an entry-level serial sensor or flowmeter and attach it to a serial-to-Ethernet converter to get your devices on the network,” he says.
　　In some cases, devices are coupled with a controller or data logger, sometimes in the same vicinity, thus negating the need for Ethernet. If the controller is central, and signals travel up to 4,000 ft, current loop RS-422 or RS-485 is preferred over Ethernet for flowmeters控制工程网版权所有, temperature sensors, and similar devices. Many such devices use 4-20 mA, digital current loop, and Modbus over