Sequence of Events vs. Historian

[sysengineer]

Would somebody mind explaining the differences between a Sequence of Events (SoE) application and a Historian application?

I am aware that some hardware vendors provide I/O cards with SoE features but i'm not exactly sure how this ties into a Sequence of Events recording application or Historian.

Thanks in advance

 

[djs]

SoE is on a millisecond to microsecond time scale. Most historians are on a second to ten second scale. SoE is used where an event can cause multiple signals, and you want to know the very first signal that arrived at the input card which is usually the cause of the event.

 

[GroovyGuy]

Howdy SysEng
Per djs's comment above, I would think that a SoE routine is the similar to a first-out routine, n'est pas?
GG

"I have not failed. I've just found 10,000 ways that won't work." Thomas Alva Edison (1847-1931)

 

[sysengineer]

Thanks for the replies. I was reading about the DeltaV SoE and it suggested that the DeltaV controller has a special memory buffer for SoE. Is it always required that the PLC/controller supports SoE? Are you generally restricted to the PLC/controller manufacturers SoE application or are there any third-party SoE providers that support multiple PLC/controller vendors?

 

[ScottyUK]

SoE recording used to be handled at a card level, then the data from the card was read by the controller and broadcast to the Historian. The controller scan rate isn't anywhere near high enough for the controller to directly trap SoE data. Recording and storage of SoE data is one of the many functions handled by a Historian, in addition to alarms, process values, trending, data archival, etc. I'm not aware of any third-party SoE handlers, although at one point Emerson were selling their eDB (Enterprise Database) Historian as a multi-platform product. I'm not sure if that is still a current product or not - it was based on the excellent WDPF and Ovation Historians.

 

[djs]

To the best of my knowledge all SoE products are hardware based, usually in the I/O module it self. You might find a third part SoE module that fits in a DeltaV rack.

 

[controlsdude]

SOE card is handling hardware signals that the scan time of the plc/standard input card can not handle. It would give you a signal either rising or trailing edge of an input, there are multiple configurations that might fit an application. Of course the input device would have to be 2x better look for this signal change. Usually the signal level of the devices and soe card are 24vdc or smaller voltage since any voltage signal input device could not match the speed of the change. Then there are the noise issues that are associated with a fast changing signal.

Of course now you need to test procedure on how you would shut machine down if your missing one of these signals. And also test for false triggers of same signal.

This card made life a pain in the but.

Historian is like everyone said is usually associated with a data logging function, not really acting on the signal just logging it for a trend.