Walchem Modbus confusion

General Discussion
1

I am connected to a Walchem Webmaster unit. The unit is used to control water treatment plants in small applications.
Anyway, there are three configurable analog inputs that include alarm setpoints. I am trying to pull the data from the analog inputs and have set up “data types”, since the addressing is much simpler this way then through the modus addressing module. I have a bit for high and high-high alarms, and the high and high-high alarm set points. I have input name, scaled input, status, and units as well. The later parameters work. The set point values are bizzare. When I set up the SQL Tags - Data Type Instance for the first analog, all works well.
As soon as I add the next analog channel, everything is fine, with the exception of the setpoint values. They either go to zero, or some other arbitrary value.
I have tried everything to correct this. The manufacturers literature indicates that the values are floating inverse. I have tried using FLOAT and INT. I have used HRF, IRI, and combination. Nope.

Any ideas would be appreciated.

2

I’m not familiar with this particular device, but here’s a couple things I’d check:
1 - Have you tried setting the “Reverse Word Order” option under “Show advanced properties?” on the device?
[attachment=0]Modbus TCP Device Settings.jpg[/attachment]
2 - Is it possible something in your UDT is using the wrong number of bits (different number expected in Ignition than actual number of bits in the PLC)?

3

You might also take a look at disabling the Allow Read/Write Multiple settings. I was communicating with a HACH unit and reading one data value was fine, when I added other values they went wacky. I ended up having to disable the Allow Read Multiple Registers Request.