How can I display historical data after moving a PLC to another port?

[Bob_L]

I have a system that has Modbus type devices on serial ports. Each device has a number of values logged (perpetually) to Citadel. Over the years the number of devices has grown and I'd like to move some of the load to other com ports. In fact I'll probably use an OPC server. What I really need is an elegant method and/or sequence to implement the changes. In particular I'm concerned about hypertrends that need to show both the before and after traces. The traces will be the same physical points, but the names will change with the new paths.

How do others handle this?

Thanks,
Bob Lockert

[Remzi]

Hi Bob,
If I understand you correctly, you are going to change the COM port settings of your Modbus object. This should not change anything on the Hypertrends because the tag addresses will not change. But using the OPCClient object instead of the Modbus object will require some modification for the Hypertrends as the paths change.
Hope this helps,
Best Regards,
Remzi A.
Applications Engineering
National Instruments

[Bob_L]

Upon reflection, I see the first part of your comment to be valid. I chose tag names that indicated port and RTU addresses. Thus Mod6_35.4xxx was device 35 on com port 6. I can in fact move some of those devices to another port by simply changing the configuration of the devices to be moved. I just can't revise the tags to show the new port and address numbers.

However, I do want to run through an OPC Server so the tag name won't and/or can't follow. They'll be different device types. I have considered changing the hypertrends to display an expression which is the sum of two separately logged items.

ie Temperature = OldLoggedTemp + NewLoggedTemp

Comments???


Bob

[Remzi]

As long as you use the expression object and make sure the expression value is logged, you should be able to display the 'Temperature' properly on the Hypertrend object.

Regards,
Remzi A.
Applications Engineering
National Instruments

[Rkdomer]

If I understand the problem correctly, you need to change the name (tag name) of your modbus objects (and/or alias names) and continue to see trend data before and after the name changes. If this is the case, check out MAX (measurement & automation explorer). MAX will let you edit object names, alias names, process names, computer names, etc. It also does other cool things like archiving data, moving or copying data to between Lookout computers, and deleting unwanted data. Lookout places a shortcut to MAX on the desktop during installation.