Error reading negative values from OPC Server

[DonTan]

I am trying to read some analog values from an OPC Server using Labview Read Tag vi. I am currently using Labview DSC version 6.1.

I have no problems reading positive values using the Read Tag vi. However, when reading negative analog values, the Read Tag vi reads the negative value as a positive value i.e. it ignores the sign of the value that was read.

I have used the OPC client supplied with my OPC Server to read the negative values and have not encounter any problems.

The tag that I have used to log the analog values is the analog tag. Can the analog tag log negative values?

Is there anything that could be done to ensure that the values are read correctly?

Wishing you Happy New Year!

[Roli]

Hi

What OPC Server are you talking about? Manufacturer?
What is the datatype reported from the OPC Server?
- You can check that if you use e.g. NI's Server Explorer, you create a group and an item and connect to the OPC server. Than you check the properties of this item.
This should give you some more information about the OPC item datatype. (see attached image)

For more info about how to troubleshoot I recommend this link:
Tools for Troubleshooting OPC Interface Problems

Let me know, or hope this helps.
Roland