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Communicate to Modbus Power Meter over Internet
Communication over Ethernet from Power Meter to remote server

Hi All

My first time so be gentle, I may ask some dumb questions as I am an Electrician but not well versed in this area.

What I am after is a simple and inexpensive way to communicate with a PMAC770 power meter over the internet so I can gather the real time and historic Data. The meter has RS 485 port and Modbus-RTU Protocol. I want to be able to connect the modem or hub that is local to the meter without the need to go through the clients PC, With the intention that the client then access that real time or historic data over the cloud.

I have some people looking at a way I can manipulate the data into graphs and dashboards from csv or excel file, I just can't find a simple way to get the data.

I did not think it would be this difficult and still don't. just think I have been looking in wrong places.

Thanks in advance for your help

By Darrin Hansen on 22 March, 2013 - 8:52 am

Hi -

My first comment would be because you apparently have only Modbus RTU at the moment, you'll have to add some sort of external hardware to convert to Ethernet, which is then routable via the internet. While there are a variety of products out there, we make a unit called the ETH-1000 ( that can convert the Modbus RTU to Modbus TCP (among other protocols). The ETH-1000 also has a dashboard tab with configurable gauges that would provide insight to your data just with a standard web browser.

In conjunction with this, I would also suggest our free Modbus master tool ( It allows a PC to be either a Modbus RTU or Modbus TCP master, and (among other functions) can log any registers you wish to a .CSV file for you to later process or graph. We even have a series of YouTube training videos on this free software.



Sounds like our product "Netbiter" will suit your needs.
Have a look at:

Hi Al,

Generically, what you are likely looking for is a Serial-to-Ethernet converter. This is a product made by many vendors, so pick the one that best fits your financial and engineering needs.

That being said, running Modbus (or any automation protocol) directly over the internet is extremely insecure. I urge you to look at the control capabilities of your PMAC770, and consider using something stronger than a simple serial to ethernet converter.

For instance, the PMAC770 offers inputs and outputs that are addressable via that same modbus. Tools exist right now that can scan the internet for modbus capable devices, and interact directly with those devices. This means they could turn devices connected to this meter on or off. Are you using the outputs of the PMAC770 to control anything that you wouldn't let a 13 year old touch? Are you relying on accurate data from this device for some other purpose?

Using a device like a bare serial to ethernet converter connected to the internet is like giving the entire world (including 13 year olds) potential control of your meter and any connected equipment.

I recommend using a product that offers the following features:
1. Uses encryption on the actual serial communication. Specifically, you want SSH, SSL, or TLS as the encryption algorithm.
2. Uses a secure paired device, where you get one device for the meter, and another for your remote computer. This way, in theory, the only system that can access your meter is the one you have specifically set it up to use.
3. Utilize a firewall, and block all IP addresses except the one you will be connecting from.

Some examples of the products I'm describing are below. Please do not take this to be a product recommendation, these examples are the result of a 15 minute google search for the specs I gave above.

I'm not sure I was very nice, but hopefully this helps.

Michael Toecker, PE
Digital Bond, Inc

1 out of 1 members thought this post was helpful...

Hi, has a Modbus RTU to XML over http which will be perfect for you application, this unit can post XML data to the cloud which mades it IT friendly.



Why not to add a GPRS IP Modem to the Meter, then its data will be sent to Server through GSM network.


Shenzhen Yinghua Technology Co.,Ltd
---Focusing On Wireless Communication


It's an option, but not necessarily secure and usually not cheap. If it's just plain old internet access, nothing has been solved.

To prevent access, the carrier would need to support a private network (i.e. a /30 subnet without a gateway to the internet or similar) for the communication. These networks cost more money to create and maintain than a normal Internet connection as well. And since that private network would need to be accessible from both sides (server and meter), it could cost twice as much for the service.

And then, the connection is still modbus, and he still needs a device to perform translation.

Digital Bond has done some research on this, and use of GPRS/3G does not necessary mean the device is safe from prying eyes. We've seen times when the GPRS/3G network offered is just plain old internet access, though I believe common carrier operators may be more knowledgeable about SCADA now.

Mike Toecker
Digital Bond, Inc