Communication options for Alicat instruments

Every Alicat device is equipped with at least one of the following communication protocols:

In this article, we present an overview of these communication protocols including electrical requirements, device and software compatibility, and network topologies

ASCII and Modbus RTU over RS-232

Alicat devices come default with ASCII and Modbus RTU over RS-232. RS-232 interfaces are useful in systems with short-range, low-speed wired data connection. This is an inexpensive option when you only need to communicate with 26 to 32 devices in low-noise environments.

Modbus RTU has a simple setup and low memory requirement compared to most industrial protocols. It also has broad support among industrial control hardware and software systems. Modbus RTU has a standard set of universal commands, making it easy to use for those who are already familiar with the protocol.

ASCII or Modbus over RS-232 specifications
  • Alicat part number: [default]; -MODBUS on older devices
  • Analog signals
  • Optional certifications: IP66/67; CSA Class 1/Div 2
  • Electrical connections: Default 8 pin mini-DIN (other options available)
  • Power over protocol connector: Available
  • Dedicated power jack: Yes
  • Additional power requirement: None
  • Available with display
  • Available via retrofitting to standard device
  • Software compatibility: Serial terminals (Alicat Terminal, HyperTerminal, PuTTy); FlowVision 2.0; LabVIEW; Modbus poll (Modbus only)
  • Max number of devices on network: 26 (ASCII) or 32* (Modbus)
    • Topologies: Linear; star

*BASIS devices can have 247 Modbus devices on a network.

Resources

Limitations

  • Lower transmission speed compared with RS-485 and Ethernet.
  • Operational across short distances only. Speed falls off considerably with distance.
  • Not usable in high noise environments.
  • CODA is not compatible with Alicat’s ASCII.

ASCII and Modbus RTU over RS-485

Choose ASCII and Modbus RTU over RS-485 if you are transmitting data across long distances or in a high noise environment. RS-485 can communicate with 26 to 32 devices at once, so larger systems will require an additional industrial protocol (see below).

ASCII over RS-485 is compatible with most devices, excluding CODA and portable options.

ASCII or Modbus RTU over RS-485 specifications
  • Alicat part number: -485; -MODBUS-485 on older devices
  • Analog signals: Yes
  • Optional certifications: IP66/67; CSA Class 1/Div 2
  • Electrical connections: Default 8 pin mini-DIN (other options available)
  • Power over protocol connector: Available
  • Dedicated power jack
  • Additional power requirement: None
  • Available with display
  • Available via retrofitting to standard device
  • Software compatibility: Serial terminals (Alicat Terminal, HyperTerminal, PuTTy); FlowVision 2.0; LabVIEW; Modbus poll (Modbus only)
  • Max number of devices on network: 26 (ASCII) or 32* (Modbus)
    • Topologies: Linear with termination resistor (120 Ohm)

*BASIS devices can have 247 Modbus devices on a network.

Resources

Limitations

  • Connecting to a computer will typically require the purchase of an RS-485 card.
  • Not available with portables.
  • CODA instruments are not compatible with Alicat’s ASCII.

DeviceNet

DeviceNet is a common choice for automation or factory-type settings and can be used to communicate with up to 64 devices. This option has the most limited options for device configurations and is only available with standard devices with no display.

device net protocol logo

DeviceNet specifications
  • Alicat part number: -DNET
  • Secondary protocol: ASCII over RS-232 (primarily for debugging)
  • Electrical connections: Male 5-pin M12 connector for DeviceNet (top port) and male 9-pin D-sub connector for RS-232 comms (side port)
  • Power over protocol connector: Required
  • Dedicated power jack: No
  • Additional power requirement: 170 mA
  • Max number of devices on network: 64
    • Topologies: Trunk with drop lines

Resources

Limitations

  • Requires a PLC.
  • Incompatible with CODA, BASIS, EPC, Class 1 Division 2, and portable devices.
  • Not available with display.
  • Not available via retrofitting to standard device.
  • No analog signals.
  • More expensive than ASCII or Modbus.
  • Requires 170 mA power.

EtherCAT

EtherCAT is the fastest industrial Ethernet technology, with data transmission rates up to 100 mbps.

ethercat_logo

EtherCAT specifications
  • Alicat part number: -ECAT
  • Electrical connections: Comms over dual RJ45
  • Power over protocol connector: No
  • Dedicated power jack: Required
  • Additional power requirement: 120 mA
  • Available with display?: Yes
  • Available via retrofitting to standard device?: No

Resources

Limitations

  • Requires a PLC.
  • Incompatible with BASIS, EPC, Class 1 Division 2, and portable devices.
  • No analog signals.
  • More expensive than ASCII or Modbus.
  • Requires 120 mA power.

EtherNet/IP

EtherNet/IP is one of the most popular industrial protocols, and can be thought of as a newer version of DeviceNet that is able to communicate with an unlimited number of devices. Like DeviceNet, it is only available with standard devices but has the added option of a display.

EtherNet/IP specifications
  • Alicat part number: -EIP
  • Electrical connections: Comms over dual RJ45
  • Power over protocol connector: No
  • Dedicated power jack: Required
  • Additional power requirement: 120 mA
  • Available with display
  • Max number of devices on network: No limit
    • Topologies: Star; linear; ring

Resources

Limitations

  • Requires a PLC.
  • Incompatible with BASIS, EPC, Class 1 Division 2, and portable devices.
  • Not available via retrofitting to standard device.
  • No analog signals.
  • More expensive than ASCII or Modbus.
  • Requires 120 mA power.

Modbus TCP/IP

Modbus TCP/IP is the simplest of ethernet protocols and was created for integration with pre-existing TCP/IP set ups. Use Modbus TCP/IP to communicate with an unlimited number of devices. Like EtherNet/IP, it is only available with standard devices with the option for a display.

modbus-logo

 

Modbus TCP/IP specifications
  • Alicat part number: -MODTCPIP
  • Electrical connections: Comms over dual RJ45
  • Power over protocol connector: No
  • Dedicated power jack: Required
  • Additional power requirement: 120 mA
  • Available with display
  • Software compatibility: LabVIEW; Modbus Poll
  • Max number of devices on network: No limit
    • Topologies: Star; linear

Resources

Limitations

  • Incompatible with CODA, BASIS, EPC, Class 1 Division 2, and portable devices.
  • Not available via retrofitting to standard device
  • No analog signals.
  • More expensive than ASCII or Modbus.
  • Requires 120 mA power.

PROFIBUS DP-V0

Many Alicat devices are available with PROFIBUS for communication with up to 125 devices. PROFIBUS is an open specification communication standard designed for automation equipment.

profibus_logo

PROFIBUS specifications
  • Alicat part number: -PROFIBUS
  • Secondary protocol: ASCII over RS-232 (primarily for debugging)
  • Optional certifications: IP66/67
  • Electrical connections: 9-pin D-sub PROFIBUS connector next to a 4-pin M8 connector for RS-232 communication and power
  • Power over protocol connector: Available
  • Dedicated power jack: No
  • Additional power requirement: 120 mA
  • Available with display
  • Software compatibility: Serial terminals (Alicat Terminal, HyperTerminal, PuTTy); FlowVision 2.0
  • Max number of devices on network: 125
    • Topologies: Linear with termination resistor

Resources

For instruments built after* July 12, 2020:

For instruments built before July 12, 2020:

*Customers with the GSD file for instruments built prior to July 12, 2020 file may continue using it with new units if your system is already configured.

Limitations

  • To communicate with the Alicat, users must have a PROFIBUS card inside of a PC or a PROFIBUS-enabled PLC.
  • Incompatible with CODA, BASIS, EPC, Class 1 Division 2, and portable devices.
  • Not available as a retrofit to standard device.
  • Not as fast as analog or ASCII serial communication.
  • More expensive than ASCII or Modbus.
  • Requires 120 mA power.

PROFINET

PROFINET is an industry technical standard for data communication over Industrial Ethernet, designed for collecting data from, and controlling equipment in industrial systems, with a particular strength in delivering data under tight time constraints.

PROFINET specifications
  • Alicat part number: -PROFINET
  • Electrical connections: Dual RJ45
  • Power over protocol connector: No
  • Dedicated power jack: Required
  • Additional power requirement: 75 mA
  • Available with display
  • Max number of devices on network: No limit
    • Topologies: Star; tree; line; ring

Resources

Limitations

  • Requires a PLC.
  • Incompatible with BASIS, EPC, Class 1 Division 2, and portable devices.
  • Not available via retrofitting of standard device.
  • No analog I/O.
  • More expensive than ASCII or Modbus RTU.
  • Requires 75 mA power.

Contact an applications engineer for support

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