Float format

Hi
I have a problem with accuracy of floatpoint values.

I have a Omron PLC acting as a slave to a Forboro ia DCS system, comms. is via seriel modbus.
The problem we have is that we don't get presice values.

DCS send 3.5 PLC show 3.47

DCS send 500 PLC show 501.2

Is your Forboro device rounding it's display and sending actual data to the PLC?

Don't think it is a rounding problem, some value display higher in the PLC that what the DCS is sending.

PS. don't no have the foxboro system works i do the PLC job.

Do you have any specs on the Foxboro system? It seems like if it was a format mismatch that the number would be off by more than just a little bit.

I was just guessing by past experience with me pulling values from an PLC that were displayed on a Wonderware HMI. The HMI rounded, and my numbers were always different.

(Or more accurately, my HMI was truncating the values then multiplying or dividing them by 10 or 100 to get the correct units displayed).

No i don't have any spec on the foxboro part. I no that the Omron plc work after IEEE 754.