Watlow Series PD VI, Modbus tcp, or Ethernet IP Examples

[HelloGary]

I have LabView 8 and a Watlow Series PD Ehternet-Enabled Temperature/Process controller that is capable of being used with a higher order controller using either Modbus tcp or ethernet-ip protocols. The Watlow users manual has provided me with all the low level information I should need (ip address, tag addresses, and data format). Is their a Modbus library for LabView 8 and do you have any examples for the library or hopefully for this Watlow device. As an alternative should I use the Ethernet-ip protocols?

[tst]

As far as I know, there is a built in Modbus library for LV 8.0 (it might come only with the DSC module). Even if there isn't, a simple search of the site should lead you to an older library, but from my quick look at it it didn't seem to be entirely developed. There are some other modbus library which can be found on the net.

If you want improved performance, I'm fairly sure that writing a limited implementation of the TCP protocol would be the way to go, but that might not necessarily be a trivial task. If you only want to send and receive simple commands, this shouldn't be a real problem, but anything more complex will require properly designing a driver. Normally this would be implemented using the TCP functions, the string functions and potentially the VIs in the Data Manipulation palette. You should be able to find example for these in the example finder.

[Doug M]

The LabVIEW 8.0 DSC Module does have built-in support for Modbus I/O Servers:

[Chris_R.]

HelloGary,

The Modbus LabVIEW Library should work fine in LabVIEW 8.0.  Although it was created in LabVIEW 7.1, opening it in LabVIEW 8.0 will upgrade the LabVIEW VIs to 8.0.  Although it has not been officially tested in version 8.0, it has been known to work.  This link will take you to the download page if needed.  Have a great day!

Chris R.
Applications Engineer
National Instruments

[tst]

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@Chris_R. wrote:

The Modbus LabVIEW Library should work fine in LabVIEW 8.0.  ...
it has not been officially tested in version 8.0

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There used to be an issue where you couldn't use that download on a 7.0 machine because it's an MSI installer and it ran only on a PC with 7.1 and only backsaving allowed using the library. Did you check to see that the installer runs fine on 8.0?

[Chris_R.]

Hi tst,

Yes, sorry I failed to mention that the MSI installer will not install this library into LabVIEW 8.0.  It has to be manually installed after running the MSI Installer or by copying the files attached below in the correct folders.  The installer for the current version of the Modbus LabVIEW Library looks in the Windows registry for the presence of LabVIEW 7.1, and will not install if the LabVIEW 7.1 registry key is not found. The installer installs two files (attached below). Make sure that LabVIEW is closed before installing.  If you cannot install because you don't have LabVIEW 7.1, all you will need to do is place the files below in the correct folder listed below.  If the library is already installed in the LabVIEW 7.1 folder, you can simply copy those files into the corresponding LabVIEW 8.0 folders.

The nimodbus.mnu file can be manually placed in the following folder:
C:\Program Files\National Instruments\LabVIEW 8.0\user.lib\

The NI Modbus.llb library file can be manually placed in the following folder:
C:\Program Files\National Instruments\LabVIEW 8.0\vi.lib\

Let me know if you have any trouble!

Chris R.

Applications Engineer
National Instruments

[Chris_R.]

For some reason, the files didn't attach.  Here they are.

Chris R.