Connect & Configure an energy meter on Modbus RTU

Hi All,

I have requested for a controller for testing purpose. My main purpose will be to test the IO points and connect a modbus meter on the RS485 bus.

I would like to know how to configure this meter inside the controller and configure the modbus register in it to read the values. Additionally will i be able to discover all the points on Bacnet IP on a third party application.

You will be able to integrate the modbus power meter into your bacnet environment easily. All the modbus registers of interest can be tied to variables in the T3 controller with a simple program like so:
VAR1 = 2MB_REG303
Where VAR1 is the local variable on the controller, 2 is the modbus ID of the power meter and 303 is the modbus register of interest on the power meter. Then on the ethernet side, you can see all the bacnet objects on the T3 controller. The local variable VAR1 will show up as AV1 in the bacnet objects list.

Thanks for the response Maurice. Let me try this and if any doubts i shall revert back.

Hi I have tried the modbus connectivity but the modbus device is not getting online in the T3000 controller. I am using T3-TB for the testing purpose.

Attached are the screenshots of the settings for your review.

Kindly advise.

Can you show us the modbus device please, if its a 3rd party device we need a small program in the t3 controller to poll the device. Please check the network programming this forum. There is lists the syntax for polling both bacnet and modbus devices from 3rd party vendors on both the Ethernet and RS485 subnets…

Maurice Duteau

Here is what I think you have there for your network setup, the item at Tab1 is a third party device on the Modbus subnet. Note that the 3rd party devices don’t show up in the T3000 left hand tree, its on the todo list though.

The commands to read a register are as showing at Tab2 (line 7) in this screen capture, the T3 controller is set up as controller number 3 as you can see at Tab8 so you need to change your program from 1.4 everywhere, to 3.4 where 3 is the main T3 panel ID and 4 is the modbus ID of your subnet device.


Other notes: Be sure to set up the RS485 subnet port as Modbus master at Tab3. You have written a program already so the network activity should start to show up immediately which you can see clicking the network health button at Tab4, it brings up the network activity at Tab5. You can also see more details by checking the network points table at Tab6 which brings up the list of all network traffic in and out of this particular T3 controller, showning at Tab7.


I have tried to connect the Power AC meter and I have got the points under Modbus subnet in the T3000 controller. However I am not able to receive points of the Energy point as I understand its a 32bit value (Long type)

Kindly advise how to proceed to retrieve the information in the program.

I’ll need a little more info. If the data is coming into a T3 controller then you can do some math on it with a control basic program and send it out through any port with any protocol. If you want to just transparently route the data from one port to another that’s also possible, let me know a few details and I’ll answer better.

I trying to read the modbus registers on the T3 controller. I have tried with the program but it seems the data is getting read by the T3 maybe due to the register type of the modbus registers.

The registers of the modbus points are all float type so do I need to write a different program for this meter.

attached image for your understanding.

Kindly refer statement 190 and on. The registers are float type (32 bit).

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Hi Maurice
im tryng to connect a level meter to T3-BB . i read about that on the furum also on the help . but controller does not read rtu from device at the most of the time .or only read once and it does not update that data again . would you please help me on this . i attached some pic from my setting and also the level meter data address .
i want to read address 99 ( Dec ) .
and its bothering when its read once data true !


the other setting

A lot of the integration questions we get can be solved with a good data capture tool. There’s so many available these days. The T3000 software does have one for Modbus and also Bacnet. If they don’t do the trick then try downloading and testing with something more advanced. We are here to help once you have done the basics.

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yes , i read this data with modbus poll software ( connect via RS485 to USB ) in my PC . there is no problem with that . my problem is how to read it with T3-BB . any information you need about Level Meter Modbus ? and wondering why T3-BB read data sometimes ? and sometime not!
did you see any problem on that ?

Here is an overview of how to program network points with the T3-BB, it shows how to address modbus devices on the IP network and RS485 subnetworks from various controllers in the system.

Refreshing of the network points is taken care of for you in the background automatically and for now there’s no user control over the polling rate. You can check the network points grid to see the remote points going in and out of the controller here. There’s no program in this controller so no network points showing in this example.


Hi Gabi,

read here. I had the same struggle polling 3-party devices with my T3-XX. Even they can be polled perfectly through various modes (modbus poll, plc, node-red), it seems that T3-XX have some problems here. Btw, Maurice, some updates about those troubles ?

We’ve made many improvements and updates since the original post, if you are experiencing subnet connectivity issues please update the T3000 application first, then update the device firmware. If you are STILL having subnet communications issues then it’ll be best to get set up with a data tap and send the detailed logs to us for a look-see. We use a tool called Docklight here for modbus RTU logging on the RS485 subnets.

One thing we see often is our device responds TOO fast, adding a delay on your device can improve communications. We have it marked down on our todo list to let the user set the delays on the T3-XX devices directly.