Distinguishing among communication options

This article presents an overview of Alicat’s various communication options. For more detailed specifications, check this page. 

Choosing the best communication protocol to work with your Alicat devices depends on factors such as: 

• Preference for analog, serial, or industrial protocol communication 
• Required operating distance 
• Required data transfer speed 
• Desired device linking configurations 
• Total number of connected devices 
• Familiarity with communication options  
• Desired data accuracy  

Alicat provides various analog, serial, and industrial protocol communication options to meet all of your specific application needs.  

Alicat analog communication options  

Alicat offers analog communication options which transfer data via either current or voltage. Due to voltage drop, current is preferable for long operating lengths. Conversely, voltage provides more control options. Compared to serial communications, analog signals may have up to 0.25% additional reading error. Alicat’s analog options include: 

• 0-5 Volts 
• 0-10 Volts 
• 1-5 Volts  
• 4-20 mA 

Alicat serial protocols  

The Alicat serial command interface is the native communications interface used for control, calibration, and programming of all Alicat devices. This interface uses ASCII over either RS-232 or RS-485, with RS-232 being the default option. This is the most powerful way to communicate with and program an Alicat device as all the in house software such as FlowVision 2.0 is built around this framework.  

Every Alicat device uses a base circuit board that is either in RS-232 or RS-485 which then communicates with a compatible industrial protocol or other control system either physically or via software.  

Alicat offers FlowVision 2.0 and Alicat Serial Terminal options for communicating serial commands with devices. Alicat’s Serial Terminal offers command line communication whereas FlowVision 2.0 is proprietary Alicat software with many different control options embedded into the program. Additionally, programs like LabView, Putty, and Python can also communicate with Alicat devices serially. Technically, some industrial protocols also communicate with serial commands however they will be covered in the next section.  

Alicat industrial protocol options 

The manufacturing controls are organized in common ways, independent of the protocols used. Some of these options involve use of process level controllers or PLCs which do small computing and control tasks. Alternatively, human-machine interfaces or HMIs display information and provide limited, programmable control over PLCs. Additionally, supervisory control & data acquisition or SCADA systems integrate data from large networks of sub-processes to make it easier to command and control entire factories. 

Industrial computers which use industrial protocol communication options are designed to be programmed by technicians already familiar with the mechanical automation and electrical relays. Because of this, they are programmed using simple, often graphical programming languages. 

Analog control is not compatible with devices using most industrial protocols (exception is Modbus RTU). All industrial protocols can run via compatible PLCs or using specialized hardware on PCs. Modbus RTU and Modbus TCP/IP require the least amount of specialized hardware to work on PCs. With exception to Modbus RTU, IP devices are not available with Basis, EPC, CSA Class 1 Div 1 or Class 1 Div 2 certified, or portable configurations.  

Alicat currently offers 7 different industrial protocol communication options, including: 

• Modbus RTU 
• Modbus TCP/IP 
• EtherNet/IP
• EtherCAT
• DeviceNET
• PROFIBUS
• PROFINET
• IO-Link

Modbus RTU  

• Modbus over RS-232 or Modbus over RS-485 communication options. 
• Openly published and royalty free.  
• Uses a master/slave architecture. 
• Does not require any special hardware configuration (works well with PCs). 

Modbus TCP/IP  

• Modbus software layer over Ethernet. 
• Works with both PCs and PLCs like Modbus RTU. 
• When using a PC, requires Modbus Poll or another Modbus program to operate. 
• Able to use remote connections. 
• Uses a master/slave architecture with no limit on total number of devices. 

EtherNet/IP 

• Device must be assigned an IP address to connect to the network. 
• There is no practical method to use EtherNet/IP with a PC. It must use a PLC. 

EtherCAT 

• Designed with short data update times allowing sub 1ms cycle times. 
• Can be connected in linear or star topologies. 
• Works with any EtherCAT capable PLC  

DeviceNET 

• Communicates over CAN (Controller Area Network) technology. 
• Supports both master/slave and peer-to-peer architecture. 
• Power is provided over the network bus. 

PROFIBUS

• Data is transferred over RS-485 serial communication.
• Requires master/slave architecture (either PROFIBUS card inside of a PC, or a PROFIBUS enabled PLC). 
• Option to power over PROFIBUS.

IO-Link

• Devices can either be configured as Class A (4-pin) or Class B (5-pin)
• The M12 port is an IO-Link port class A with 4 pins or an IO-Link port class B with 5 pins
• The device can be powered through the M12 connector
• Port class B uses the isolated power supply for valve power, most commonly for instruments with large valves