Easiest way to map Modbus meters to BACnet is to do no mapping

by Albert Putnam October 14, 2014

Can a user get BACnet data from Modbus meter without any mapping?

As we wrote in our previous blog posts, energy consumption data can help building operators and engineers to better manage their facility's energy use. Many facilities have Modbus meters for measuring energy usage and BACnet for Building Automation system.

Is there easy way to convert data from Modbus meters and devices to BACnet without any manual mapping?  We know there is with the Cimetrics BACnet Interface to Energy Meters (B6030).

The ease of use comes from the efforts of our developers and analysts creating mapping templates which are pre-loaded in the B6030 and require no manual mapping by the user. Just select a meter template (where the mapping is already defined), meter IP address and ID and you are good to go.

 

Mapping

Why did we create this interface instead of having a CSV mapping file? Well – if you look at a general Modbus to BACnet gateway it requires you to learn:  

  • Modbus registers of Modbus device of interest.
  • How to select the best Modbus register data (or compositions thereof).
  • How to create meaningful BACnet names, units and descriptions for the data.
  • The structure of template and its allied toolkit and semantics.
  • Process of loading it.

So we are looking at a steep learning curve for the user, and even then there is no guarantee that the mapping will be meaningful. For every register we chose a meaningful name on the BACnet side instead of each user coming up with some random names. We also chose what meaningful registers to expose, thus saving time and resources for the user. The mapping from B6030 turns out the same way every time, in correspondence with existing BACnet and domain and industry best practices.

Instead of the user spending time understanding what the points in the devices mean and how they can be best named we did all the work upfront. We predefined the mapping for numerous meters and loaded them into B6030. Of course someone might say – “what if I want kW versus W” or “I prefer English to SI units”.  One  expects exponents in BACnet  – not changing data prefix/magnitudes as one prefers. Having the same meaningfully consistent named and unitized objects gives a user clarity and stability. One will not expect look at an object today and see it has kW and then look at the object tomorrow and see W. One will see the same consistent data all the time. Clarity, stability and adoption of domain best practices – is what we all want.

So what is the mapping template and how do we do it? More about it in our next post – stay tuned.




Albert Putnam
Albert Putnam

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