TEC 800 series control using modbus

[Uottawa]

Hello

I am currently trying to write a program that would be able to control TEC 800 series from alpha omega intruments. Although I have done programming for other devices before, such as Keithley, this time I came across something that I've never seen before. This device is operating using modbus. I am having a difficulty understanding how do you communicate with modbus. I have downloaded the modbus library with the necessary VI's that should be sufficient to communicate with TEC 800 series. Any help, info, would be greatly appreaciated. 

Thanks

Viktar Tatsiankou 

[David_Pratt]

Hey Viktar,

There's a great document about ModBUS here from NI's website. It explains the protocol and concept in depth.  Let me know if this helps!

[Uottawa]

Thank you for the tip, I did go over this document before, however, all I am really interested is to grasp an idea of how to read and write to the instrument equipped with RS-232 connection. I have downloaded the library of modbus VI's and  far as I know there is a VI's called MB serial query, which can either read or write. The problem is I just have no clue of how to use this VI to communicate with my device, as it is not as simple as GPIB or VISA write VI's. If anyone have any experience of communicating with device that uses modbus or simply have  an idea that will help me to move forward, please reply

Thank you

Viktar Tatsiankou 

[David_Pratt]

Hey Viktar,

To start your modbus communication you need to setup your VIs like the Modbus Start photo shows.

Make sure to set the baud and other settings appropriate for your specific device.  Once that is done then you need to edit the Modbus Command cluster as shown on the front panel photo to Write instead of Read for your appropriate action.  I believe this addresses your inital inquiry about how to make the MB Serial Query vi send or write.

Message Edited by David P. on 01-09-2009 01:34 PM