Adding Modbus register values together


Thread Starter


I have a situation were I need to do some metering for distributive generation around a hotel property. The data needs to be accumulated and sent to the local utility as a single set of data.

The inverters already have MODBUS, TCP or RTU, with all the data I need. I could do a wireless network and have done so in the past for both ethernet and wireless MODBUS RTU, so I think this should be fine.

The problem I'm facing is how do I add multiple registers together? Then how do we export that sum as a single register?

I figure this would have to be done with software but on what platform and what software. I guess what I'm looking for is an off the shelf product that has these capabilities. If not then I will have to have someone build if for me.

Thanks in advance.
I have a solution in which you will also have a display of the values and the sum.

Using our TPD-433 (1 Ethernet port and 1 RS-485 port), you can connect the 2 meters as Modbus RTU slave devices to our TPD's RS-485 port. The TPD will be a Modbus RTU master to the meters. After connecting, you can create a virtual register and add the two values (in float or integer) and share the data as a Modbus TCP slave device through the Ethernet port.

You can also create some simple label widgets on the the 4.3" touchscreen to display the value with a nice background.

Here is a link to the product if you are interested.
TPD-433F (flange mount)

We also have a TPD-283U if you want a smaller cheaper version.
Where would I find the instructions on how to connect the modbus TCP devices and how to add the data in the HMI platform?