Communication protocols: Talking to your Alicat device

An Alicat mass flow or pressure control meter is a feature-rich, multi-variate instrument that outputs a large amount of data. It’s not just a black box with analog input and output. It shows unit ID, absolute pressure, temperature, volumetric flow, mass flow, set point and gas type. Any of those scientific parameters can be set as the dominant feature on the display. However, there are many additional ways to communicate with your Alicat. Because of its versatility, it’s important to choose an ideal form of communication and interaction with the instrument that fits the application. The most basic option is to use the easy-to-read, backlit LCD panel on the front of the device.

  

Supported Protocols

The most straightforward way to send and receive commands and data to and from the unit and an external device is to connect a standard DB9 cable to the back of a computer equipped with an RS232 port. This allows the user to talk to the Alicat digitally, send and receive commands and retrieve data. RS232 is the most feature-rich way to digitally communicate with our devices. Alternatively, you can use RS485 if you need to run a line for thousands of feet. The high speed data communication offered by standards like RS232 and RS485 allows the user to do much more from an external device that could ever be done from the front screen/buttons.

To communicate with other equipment and/or networks, we can employ internet protocols, ethernet-based protocols, Modbus RTU, Modbus TCP/IP, DeviceNet, Profibus, EtherCAT. To accommodate legacy systems, analog signals like 4-20mA, 0-10 volt or 0-5 volt are always available. The default protocol for new instruments is ASCII because of its versatility. Other available options can be chosen when ordering.

Connecting Multiple Devices

We’ve engineered a multi-drop version of our communication language that allows up to 26 devices to talk on the same RS232 network in parallel. By assigning each with a letter of the alphabet, the named instruments will only respond when they are addressed by their corresponding letter. This solution allows us to get around the limitations of a typical serial communication path.

Important Considerations When Choosing a Protocol

There are almost 40 industrial protocols in use today, some dating from as far back as the 1970s. To be compatible with them we have a large host of existing protocols and we add more every year.

Backlit color TFT display

Backlit color TFT display with backlight toggle button

The key point to consider when choosing a protocol is knowing the existing set up. For example, a small laboratory starting from scratch interested in getting the experiment up and running quickly would be best served using RS232 connected to a computer. Even more simply, they could use the six buttons on the front panel, right out of the box. However, if a large factory is integrating an Alicat into a system with potentially hundreds of other existing devices on a common network, we can usually accommodate the protocol that allows the device to integrate into the factory’s system.

Why Choose Alicat?

Our devices can accommodate a large number of protocols. We can replace components to simplify systems and integrate them into already existing networks. We work with our customers to determine the best solution for their application, then build the mass flow or pressure control meter that meets their needs. We think about communication protocols, electrical connections, plumbing and other case by case variables. Not only do we engineer the project from beginning to end, but we remain available for installation, troubleshooting and at annual recalibrations.

Simply put, we don’t just sell flow meters and pressure controllers. We sell custom solutions for varying and evolving technological problems. Contact one of our Application Engineers to discover the ideal solution for your unique flow and pressure control needs.

 

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