Communications Protocols

Communicating with your instrument

Analog, digital and industrial communications

Connect to your Alicat using your company’s communications standard. Both legacy and modern industrial communications protocols are available as add-on options for many of our instruments, which otherwise include both analog and digital communications natively. Alicat’s default for most instruments is 0-5 volt analog signals and RS-232 serial communications, both carried via our 8-pin mini-DIN connector. Communication protocols, connectors and pinouts are customizable at the time of order.

Industrial Protocols

Speed up your industrial communications network by adding your industrial protocol directly to your Alicat flow or pressure controllers. All industrial communications are handled directly within our instruments, so you don’t need to slow down your process with a separate translator box.

Available Industrial Communications Protocols

  • DeviceNet (DNET) includes male 5-pin DeviceNet connector on top and male 9-pin D-sub connector on the side
  • EtherNet/IP (EIP) includes two RJ-45 connectors on top with green and amber status lights
  • EtherCAT (ECAT) includes two RJ-45 connectors on top with green and amber status lights
  • Modbus-RTU (MODBUS) includes Alicat’s standard 8-pin mini-DIN connector by default, but can be ordered with any other connector type
    • The Modbus-RTU protocol can be ordered with our default RS-232 serial interface or RS-485 interface.
  • Modbus-TCP/IP (MODTCPIP) includes two RJ-45 connectors on top with green and amber status lights
  • PROFIBUS DP-V0 (PROFIBUS) includes a female 9-pin D-sub DP connector on top and female 4-pin M8A power connector on top.

Download our white paper: Taking the Leap from Analog to Digital for Multivariate Process Control in Manufacturing (PDF).

Select your industrial protocol below

Use the tabs below to view information and available downloads for your industrial protocol.

device net protocol logo

Automation industry users looking for mass flow control with DeviceNet language capabilities turn to Alicat Scientific for DeviceNet-conforming instruments. Alicat is a member of ODVA, the DeviceNet certification body, and our DeviceNet instruments are ODVA CONFORMANT™.

For more details about using DeviceNet on your Alicat instrument, read our DeviceNet FAQ.

DeviceNet Operating Bulletin DeviceNet EDS file ODVA Declaration of Conformity


ethernetip protocol logo

EtherNet/IP industrial network protocol is available on Alicat mass flow and pressure instruments purchased with the EtherNet/IP option. Automate your flow and pressure control system through an Ethernet cable connection. The protocol must be ordered as an installed option for new instruments, and is not available as an upgrade to existing units. Alicat is a member of ODVA, the EtherNet/IP certification body, and our EtherNet/IP instruments are ODVA CONFORMANT™.

For more details about using EtherNet/IP on your Alicat instrument, read our EtherNet/IP FAQ.

EtherNet/IP Operating Bulletin EtherNet/IP EDS file ODVA Declaration of Conformity


The EtherCAT protocol is available on most Alicat flow and pressure instruments. Like Ethernet/IP, EtherCAT uses ethernet cables to achieve very rapid data transfer rates for hundreds or thousands of devices on a single network.

EtherCAT Operating Bulletin EtherCAT ESI file


The Modbus-RTU communication protocol has been helping manufacturers for over thirty years, making Modbus the linqua franca of the industrial manufacturing world. Devices ordered with the Modbus-RTU application layer communicate over serial RS-232 or RS-485. Modbus data may be transmitted through Alicat’s default 8-pin mini-DIN connector, a 9-pin or 15-pin D-Sub connector or an RJ45 connector.

The Modbus-RTU poll configuration file below loads the configuration requirements required to read the available data registers on any Modbus-equipped Alicat device. This is useful for troubleshooting and viewing the required Modbus data settings.

Modbus Operating Bulletin Modbus Poll Data Registers – MBP file


Devices ordered with Modbus-TCP/IP supports standard 10BaseT and 100BaseT Ethernet communication. PLCs running the Modbus industrial automation protocol over Ethernet cable can connect with Alicat instruments using the Modbus TCP/IP protocol option.

All the mass flow or pressure controller’s data, including: mass flow, volumetric flow, pressure, temperature, selected gas calibration, setpoint, and totalized flow can be output to a central PLC running Modbus TCP/IP. Users may also change setpoint or gas selection, and issue other commands remotely. These capabilities are available in a Modbus intranet or internet environment, using the TCP/IP protocol.

Modbus Operating Bulletin

Alicat instruments ordered with PROFIBUS include a female 9-pin D-sub DP connector on top and female 4-pin M8A power connector on top.

The following options are available for instruments ordered with PROFIBUS communications.

  • Power Over Profibus (POP) routes power through the top DP connector instead of the side-mounted one.
  • Preset Unit ID sets the unit identifier numbers for your instruments at the factory (default Unit ID is 125).

For instruments built after July 12, 2020:

For instruments built before July 12, 2020:

Note: 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.

Serial Interfaces (RS-232 and RS-485)

All Alicat instruments ordered without an industrial protocol include digital serial communications for easy transfer of flow data to a computer or PLC. Default serial communications for most instruments is RS-232; FP-25 instruments use serial communications over a USB connection. Alicat’s implementation of RS-232 is multi-drop, just like RS-485, and can accommodate up to 26 different instruments on one network.

Available Serial Interfaces
  • RS-232 (default) multi-drop serial protocol
  • RS-485 multi-drop serial protocol

Several options are available to set up your serial communications preferences before we ship your instruments to you:

  • Preset Unit ID (ID:) sets the unit identifier number for your instrument (default Unit ID is A).
  • Preset Baud Rate (BAUD:) sets the baud rate for your instrument (default is 19200).
  • Preset Streaming Rate (SR:) sets the serial streaming rate for your instrument (default is 50 ms).
  • Preset Streaming Mode (STR) presets your instrument to ship to you in streaming mode instead of polling mode.


Analog Signals

Most Alicat instruments come with analog outputs; flow and pressure controllers also include analog input signals. Many instruments can also carry a secondary analog output signal, which is entirely independent of the first. Analog signals are called out in the adder code portion of Alicat part numbers.

Available Analog Output Signal Types
  • 0-5 Vdc (default) for mass flow (5M), volumetric flow (5V), pressure (5P) or temperature (5T)
  • 1-5 Vdc for mass flow (1M), volumetric flow (1V), pressure (1P) or temperature (1T)
  • 0-10 Vdc for mass flow (10M), volumetric flow (10V), pressure (10P) or temperature (10T)
  • 4-20 mA for mass flow (CM), volumetric flow (CV), pressure (CP) or temperature (CT)

Secondary analog outputs can be used to transmit data for the same flow parameter to a second receiver, or you can use it to send data for a second parameter altogether. It is not necessary for the secondary analog output signal type to agree with the primary output signal type (e.g., 0-5 volts). Secondary analog output signals are indicated with a “2” placed in the middle of the above adder codes (e.g., 52M, 12V, 102T or C2P).

Available Analog Input Signal Types

Analog setpoint input signals are available with the same signal types as the output signals above.

  • 0-5 Vdc (default) setpoint input (5IN)
  • 1-5 Vdc setpoint input (1IN)
  • 0-10 Vdc setpoint input (10IN)
  • 4-20 mA setpoint input (CIN)