Using 1756-MVI (MVI56E-MCM) with Endress & Hauser Rackbus flow meters

We have a contract to refurbish/upgrade a filling/bottling machine. We have the machine but not its control panel or PLC.

We've built a new control panel based on the original drawings. We've changed the obsolete 1756-MVI/A serial comms modules to ProSoft MVI56E-MCM modules.

These two comms modules are to talk to sixteen (16) Endress & Hauser Promass 63MT08-WOW00A9092B mass flow meters - each module talks to 8 of the 16 meters on separate RS-485 networks.

My problem at the moment is that there seems to be no way of knowing the port configuration parameters (i.e. baud rate, data bits, stop bits, parity etc.) without having the original 1756-MVI modules. I should add that these meters are 'blind' with no built-in keypad or display for programming or querying the program.

I've approached E&H in the hope that they would have a method of extracting the configuration from the meters but they are saying that the meters are so old that all their expertise and equipment for performing such a task is no longer around.

I'm going to attempt to track down the original equipment manufacturer in the hope that they may have kept records.

Other than connecting up to a meter and trying multiple combinations of settings in the hope that we hit on the right one, does anyone have any ideas on how we can make progress with this?

Also, the meters use what appears to be E&H's proprietory Rackbus protocol. The original 1756-MVI modules could talk to them (presumably!). Any ideas if the new ProSoft modules will be able to?

As far I know, 1756-MVI/A is basically the same as MVI56ADM: a module made for manufacturers to design their own serial protocols. The programmer has to write the code using C language, compile & download it to the module.

That said, you can use an MVI56E-MCM if the protocol written for the MVI was compatible with modbus serial.

Thanks, nhatsen.

My boss tells me that someone at ProSoft told him that the MVI56E-MCM modules were the ones we needed to replace the 1756-MVI modules but it's contradicted by what you're saying and everything I've seen on the ProSoft website which also seems to say that the MVI56-ADM is a direct replacement for the 1756-MVI.

Nothing I've seen in the limited information I've been able to dig up on the Endress & Hauser meters indicates that they are capable of Modbus communication. As we also don't have the code for the original 1756-MVI modules and we have no information on this Rackbus protocol to be able to re-write it, we could be looking at having to replace all sixteen of the flow meters.

As stated by nhatsen MVI56E-MCM speaks modbus serial only. Unless your flow meters are configured to use Modbus serial, tinkering with the serial settings will not only be shooting blindly, it will be shooting without a target.

Even if you had the right programmable module, you would still need to know how to write the Rackbus protocol. Using such a niche protocol really hinders progress when someone else takes over, hence I'd advise you to replace your flow meters with new ones that speak Modbus serial.

Unfortunately that is going to cost you a pretty penny!

Just to conclude this. We ended up having to buy the MVI56-ADM modules. The machine manufacturer was still around and was able to supply the Rackbus protocol code that they'd written some years before (at some significant cost to our customer). It took a little while to get the meters talking to the modules but eventually, we got there. The machine shipped a little while after and our customer is getting good results and is very pleased with it. Thanks for your help.