Modbus RTU Connection

[NiFred]

Hi everyone!
I’ve got a Modbus RTU flow meter installed in a pump house that’s pretty far from our central SCADA room. Running a new cable isn’t really an option right now because the route would have to cross a road that we’re not allowed to excavate.
My data-logging software only supports Modbus RTU over a serial COM port. Is there a way to bridge the connection to the remote meter without installing a physical gateway or having to reconfigure the software?
Curious what solutions others have used for similar long-distance metering setups.

[nctnico]

If you have Wifi or a network between the locations, you can use a serial port or USB port over network extender. These boxes can be bought off-the-shelve. It won't be as reliable as a cable connection though.

[Siwastaja]

Just Google RS485 wireless bridge - plenty of offerings. Our experience on these is limited, but we know a few installations where they did work for modbus RTU.

With wireless on the ISM bands, nothing is guaranteed, though. Someone else might be legally colliding with your frequency and you start losing packets.

These usual bridges would work in the ~1-2 kilometer range, given line-of-sight with no obstructions. So the solution depends on what "pretty far" means.

[indeterminate]

Moxa makes reliable serial Ethernet converters that just work

https://www.moxa.com/en/spotlight/serial-connectivity/nport-serial-to-ethernet/index

Siemens is another option
https://www.siemens.com/en-us/products/ruggedcom/

[cburgess]

Had the same problem 20 years ago - only with getting data from a remote site a few miles away, line of sight.

We ended up using a couple radio modems ( licence free ) from a company called Elpro. 
It just worked - as if we had a physical wired connection between the two points.
Had a quick look at the website - the radio modem we used is long-gone obsolete - but there looks to be other similar products.

[Perkele]

Baud rate?
How often do you need to send/receive the packets?
Only reading the data, or do you also need to write/set/control something?

[Semon]

I’ve dealt with something similar before. https://www.serial-over-ethernet.com/modbus-rtu-over-network/ explains the general idea pretty well. You’d run a small utility on a PC at the pump house and another on your SCADA PC to pass the serial data between them over the network. It creates a virtual COM port, so your data-logging software can keep working as usual. You’d just select the new port in the software. Since the utility forwards the data without translating the protocol, the Modbus RTU frames stay intact.