I have an Omega CN7200 PID temperature controller that I’m trying to talk with using VBA code and NI-VISA. The CN7200 has a RS-485 bus, but I bought a 485-to-USB converter from Omega. As a test, I loaded Omega’s SW and the 485-to-USB driver, and I can read and write the CN7200 registers just fine.
There is no NI-VISA driver specifically for the CN7200. There is one for the CN7500, so I downloaded the NI-VISA driver for this. Since the CN7200 and CN7500 use the same Omega user’s manual, I’m hoping this driver will work. However, while the NI-Max sees the 485-to-USB converter on COM6, when I do a IDN query I get this message: “Read Operation Error. VISA: (Hex 0xBFFF0015) Timeout expired before operation completed.” Another window says “Return Count: 6 bytes”. So it seems like data is being read but not recognized.
Any ideas on how to troubleshoot this? (I’ve tried changing the NI-Max baud/data bits/stop bits/term character, but nothing seems to help. I also extended the time out to 2000ms.)