Industrial RS485

RS485 is widely used for industrial device communication. The RS485 standard allows equipment to be multi-dropped operated over long distances in electrically noisy environments.  RS485 utilizing a 3 wires ( +, – and Ground) bus allows connection of up to 32 multi-dropped devices at distances up to 4000 feet at baud rates ranging from 1200 to 115,200 bps. RS485 communications used to bus smart instrumentation and controllers in SCADA and automation systems.

SCADALink RS485 Products … see comparison

SCADALink has designed a complete set of easy to use and rugged solutions for Industrial RS485 use including  conversion, isolation,splitting, and multiplexing RS485 signals used in Industial Applications.

A key feature of the SCADALink RS485 Devices is that they are  designed for  industrial applications:

• Class I Div 2
• -40 to 70 deg C Operation
• DIN Rail Mounted
• 10-30 VDC Wide Voltage Range Operation
• Low Power Operation
• Terminal Block Connectivity

SCADALink RS485 Products are designed with various combination  of conversions and isolation for versatility. This allows a minimum number of devices to be installed in an application.

Conversion (RS232, USB, and Ethernet)

SCADALink Devices that support RS485 include devices that convert RS232, USB, and Ethernet to RS485 devices. RS232 to RS485 conversion is used to connect modems, computers, and PLC with RS232 connections to devices that connect via Rs485. USB to RS485 conversion is typically used to allow laptops or computers to connect to field instruments for maintenance or diagnostics purposes. Ethernet to RS485 conversion is used Ethernet based devices  are required to connected to industrial devices with RS485 connectivity.

Isolation

Isolation for  RS485 networks is used on RS485 networks with longer cable runs to prevent ground loops and surges from affecting RS485 communication links. Both the SCADALink TISC-485 and RS485HUB  incorporate isolation.

Splitter Operation

The RS485HUB is a 3 port isolated RS485 HUB that provide 3 independently isolated RS485 ports from a RS485, RS232, or USB source. Each port can connect to 32 RS485 connections. The use of RS485 Hub is recommended for system architectures where there are instruments located further away wired in a star topology. The use of separated  isolated RS485 ensures adequate signal levels to each circuit ensuring reliable communications.

LOI Override

The RS485HUB, TISC485, and the SS20 have a LOI Override mode which allows a USB connection to override and direct connect to the RS485 Output. This enables maintenance and configuration of equipment on the RS485 multidrop without disconnecting of wires just by connecting the USB Port.

Multiplexing (Muxing)

Muxing allows  multiple masters to communicate to the same RS485 device network. The SCADALink IP100, SS10, and SS20 perform this operation.

Connectivity

RS485 is commonly used in the following devices:

• RTU
• PLC
• Loop Controllers
• VFD
• Smart Instruments
• EFM
• Power Meters
• Remote I/O

SCADALink RS485 Device Functionality Comparison (see table)

Devices			2-Wire or 4 Wire	Isolation	Splitter Operation	Conversion			Multiplexing	Notes
						RS232	USB	Ethernet
1	IP100		2 / 4			✓		✓	✓	A
2	SS10		2 / 4			✓			✓	A
3	SS20		2	✓		✓	✓		✓
4	TISC485		2 / 4	✓		✓	✓
5	RS485HUB		2	✓	✓	✓	✓
6	USB		2 / 4				✓

Notes:

A. Multiple Master to Single Network