Mettler Toledo IND570 to Citect communication

Hi all,

I have a client asking for some advice about installing an IND570 weigher and having Citect read out of it directly using the Modbus TCP option card, bypassing any PLC's.

The problem is that the manual explicitly specifies the data be read out by a PLC and I can see that the reason is the weigher comms aren't exactly the most straightforward.

Basically the way I understand it is that each scale only has a single Modbus float register dedicated to weigher readings. The Modbus master needs to write command words to trigger dynamic population of said register with the desired reading (gross, net, etc.). The intention seems to be that PLC logic be written to cyclically read out different weights out of the one register.

Fortunately, the client only really wants net weight readings which seems simple enough because that will only require the same command each read. So my theory is to make a dummy Citect tag with a statically defined command word and feed that to the IND570. On paper, this should allow Citect to constantly read out net weight from the IND570. Can anyone with experience with this setup let me know if this will work or if I'm on a fool's errand?

Thanks

I recently used the profibus version of the scale, I didn't have to send a command word, I just read the 4 SINT and then swapped them in the PLC to get the floating point.

the only thing I had a problem with was some data addresses that I was reading but not using had values on it and was stopping me from reading the scale properly, once I set those to zeros it worked fine.

I use the IND570 all the time with PLC's, but I've never tried to display the data directly on a SCADA system without involving a PLC.

I don't think it'll work. You might be able to have the SCADA read a modbus TCP tag directly from it, but something has to send a command word to the IND570 to tell it what data to report back. I'm not sure how you'd go about that without establishing an implicit I/O connection.

Having said that, I use Ethernet/IP not Modbus TCP (same physical card, but different protocol), and I'm not especially familiar with Citect. So I wouldn't bet the farm on it being impossible. Interested to see if you find a way to do it!

Not the most interesting of updates, but for now we essentially recommended that the client go with a PLC solution anyway. He started asking about some data processing functions (moving averages, etc.) that pretty much necessitated a PLC regardless.