Watlow F4 and Modbus

[Peter256]

Dan,

The F4 ships from the factory with a default baud rate of 19200. Your comm port must be the same. Your computer might be set to 9600 baud. Either make sure your comm port is 19200 baud or change the F4 to 9600 baud.

Peter
TestEquity LLC

[jonwilson]

Hi Peter,

Thanks for the quick response.

Yes my PC com setting is the same as the F4 Controller. I was able to change the controller temperature unit from F to C or vice versa.

But I was unable to read anything from any of the holding registers.

Please advise.

Thanks

Dan

[Joe_Gerhardstein]

Dan:

I was never able to get my Watlow to reply to any queries.  We wound up needing to track the case temperature of a powered device in the chamber, so I ended up writing a closed-loop controller in LabVIEW for that with a separate thermocouple, and just doing blind sets to the Watlow.

Did you try sigaman's suggestion of making sure you have the latest firmware on your controller?


Joe

Message Edited by Joe Gerhardstein on 01-16-2007 08:47 AM

[falkpl]

I had a heck of a time getting the watlows to communicate with the PC using both the modbus libraries and writing my own visa commands.  I dod get it to work though (It was my first attempt at modbus).  The main culprit was the baud rate.  The client insisted that they had set it to 9600 and the manual did state that the modbus is to be set to 9600 but it was 19200.  Once the settings were correct I had little problem using visa to communicate with the watlow using my own string parser and simple visa com writes and reads.  Dont give up, start simple and pass the example strings (make sure you are in hex string mode) and see if you can get a valid response.  Good luck.

Paul

[Peter256]

Dan,

I have a collection of drivers that I know work. You can contact me at the phone number on my website.

Peter Kesselman
VP Product Marketing
TestEquity LLC
http://www.testequity.com

[fzhong]

I am able to use the instrument driver from NI's site to read Input 1 temperature and control the Digital 1 Output.

I could not find a VI library call to change the value to SP1.

I would appreciate if anyone can enlighten me.

Regards.

[Joe_Gerhardstein]

fzhong:

For my F4, I write to a Single Address starting at 300.  See attachment for a wrapper I wrote around the ModBus libraries.