09-16-2008 12:36 PM
we are using Signal Express to do our data acquisition. Since Signal Express can connect directly to the OPC server of the cFP, we have to do the acquisition from the shared variables of the cFP.
The problem is that we have custom scale in our AI-111 module in the cFP and those scale are not working when doing the acquisition with Signal Express. I think this is a bug (like the shared variables doesn't used the scale), since if we connect directly to the OPC server of the fieldpoint, the value are scaled correctly.
Software used : MAX 4.5, Fieldpoint 6.0.2, Signal Express 3.
09-17-2008 04:57 PM
You will need Full Edition of LabVIEW Signal Express to use shared variables. What is the difference between the actual scale and it you are using with Signal Express?
This knowledgebase might come useful.
09-18-2008 12:10 PM
we do have the full edition of Signal Express, this is not the problem. We are already logging the information comming from our cFP-1808 : TC-120 and AI-111 module. The problem is that the AI-111 module is a 4 to 20mA module, and we have thermocouple connect to it. We want to read temperature in Signal Express instead of mA.
There's a option in MAX where you can add scaling to a cFP module. This scaling work in MAX, in the OPC server of the cFP, but not in Signal Express. In Signal Express, you still read the mA value.
I know we can add a formula in Signal Express, but we don't want to do that, when there is an other option in MAX.
09-19-2008 01:55 PM
Custom scaling in MAX is a part of the IAK file and is local to MAX. Features that are available in MAX are not necessarily available in Signal Express. MAX is used to configure systems (in most cases) rather that perform and store data acquisition.
The only way to set a scale in Signal Express is to use a formula with cFP.
09-22-2008 07:32 AM
If I understand correctly, there's no point of having this custom scaling function ? If this option is only local to MAX why is this option available ?
I've looked correctly and the scaling function is "exported" outside of MAX, since if you connect to the FieldPoint OPC Server (National Instruments.OPCFieldPoint), the value of the AI-111 module using are using the scales.
I just don't seem to understand, why the scaling are not appliyed to the shared variables too...
09-22-2008 10:28 AM
Is the Shared Variable Engine running on the host PC that is running Signal Express or on the FieldPoint? If it is on the PC, then try on the FieldPoint. I suspect that the problem is in how the Shared Variable binds to the FP I/O. One way around this is to embed a vi on the FP that reads the I/O and updates the Shared Variables.
09-22-2008 11:54 AM
the fieldpoint backplane we are using is a cFP-1808, without embedded memory. So I don't think we can insert a VI in it. I don't know what you mean by is the Shared Variable engine is running on the PC. (Like look for task xxx.exe in the task manager ?).
We can read those shared variables in Signal Express, the problem is that the custom scale aren't apply on our measurement. (but they do on the OPC Server).
09-22-2008 12:56 PM
Sorry I missed the fact that you were using a cFP-1808 and did not have a cFP processor module available. I did find a document that discusses using scales with LV 8.0 and above and I believe may be related to your problem. http://digital.ni.com/public.nsf/allkb/5A1BEE79660CBBAB8625712D00766FE1
09-22-2008 01:02 PM
this knowledgebase may in fact show why it's not working in SE. I just don't understand why it's been developped this way. NI seem to have forget everyone working with cFP and want to do acquisition.
I just don't understand too why the variable are scaled in the OPC server, and not in the shared variables...
09-22-2008 01:46 PM
Can you give me a few more details as to how you created the Shared Variables that are bound to the cFP I/O? Was this done from within a LabVIew project?