programmatic OPC Quality

[oceanwanderlust]

On a Omron CQM1 CPU21, I’m incrementing a DM location and then reading the value of this location via OPC (DA 2.0 using Open Data Server and/or Kepware). Since I programmatically incremented the value, the resulting OPC Quality is always Good. Is there a way that I can programmatically force the Quality of this data location to be Bad, Unknown, etc?



thanks!



joe

 

[BobB]

If you are reading BCD numbers then write #FFFF to the data location - this may do it but I do not know. I do not particularly like OPC quite frankly.

 

[oceanwanderlust]

Writing FFFF to the memory location and then trying to read the OPC item would probably result in Engineering Units Exceeded.

In some OPC documentation, I found the Quality BitField; QQSSSSLL, but I still do not know where this memory location is so that I can manipulate it within my ladder program.

Since the OC Quality is used to propagate the state of a sensor attached to the PLC, it seems very likely that these bits are accessible, but Omron's documentation does not mention it anywhere that I've found.

Yea, I have my gripes about OPC too. Then again, I have my gripes about sitting infront of this computer when I could be our surfing.

Anyways, any further pointers would be greatly appreciated!

joe

 

[oceanwanderlust]

still looking for an answer...

After not receiving a response from Omron Tech support via email, I gave them a call this morning...

Unfortunately, I still don't have an answer. Everyone knows that the Quality is bad when the PLC is disconnected, but noone has been able to explain how I set Quality, such as Sensor Failure, Device Failure, etc.

Can I not do this because I have just have basic digital input modules on my PLC? Would all of this quality become transparent if I had an analog module hooked up to an analog sensor? Even so, I'd guess that the ladder program would still need to access these quality bits.

 

[BobB]

Have you had a look on the Microsoft site at all? There may be something there.

 

[Paulus]

Everyone knows that the Quality is bad when the PLC is disconnected, but noone has been able to explain how I set Quality, such as Sensor Failure, Device Failure, etc..

Hello OceanWanderLust,
The quality that you speak of with OPC, is the quality of the data itself (i.e. the connection), not a value.
So if you have a Sensor failure, the values currently in the DM area will still be read succesfully by the OPC server (whatever the values), and the quality would still be good.
I may be wrong, but I believe what you are asking is not possible. I think that you need to manipulate your ladder program in order to detect sensor failure etc, then flag that error condition as a seperate alarm or whatever.

Hope this helps.