Trend process - Johnson Controls - LIT-1201668 - System Integration - LonWorks Integration - 12.0

LonWorks Network Integration with Network Engines and LCS Technical Bulletin

Brand
Johnson Controls
Product name
LonWorks Integration
Document type
Technical Bulletin
Document number
LIT-1201668
Version
12.0
Revision date
2022-08-30
Product status
Active
Language
English

The following example shows a step-by-step trend process. Figure 1 shows this same process graphically.

The following trending example assumes:

  • field value is a linear, increasing value

  • trend interval is 60 minutes (3,600 seconds)

  • Temporary Status Item Expiration Time is 60 seconds

  • initial field value is 71.8

  • Present Value is not updated by any other means

Trend process example:
  1. Trending begins when the network engine receives a trend request for the trend point’s Point Value (PV). Trending reads the initial PV at 9:00 A.M., which is 0.
  2. Polling begins and the Temporary Status Item Expiration Timer starts.
  3. Polling acquires the point’s current value and stores it as the update value of 71.8. At this point, the trend has a value of 0 with a timestamp of 9:00 A.M., even though the actual field value is 71.8.
  4. Sixty seconds later at 9:01 A.M., the Temporary Status Item Expiration Timer expires and polling stops (PV is now 72.0).
  5. Fifty-nine minutes later at 10:00 A.M., the hourly trend request restarts the trending process and reads the last stored PV (72.0).
  6. Polling begins and the Temporary Expiration Timer starts.
  7. Polling acquires the point’s current value and stores it as the update value of 74.1. At this point, the trend has a value of 72.0 with a timestamp of 10:00 A.M., even though the actual field value is 74.1.
  8. Sixty seconds later at 10:01 A.M., the Temporary Status Item Expiration Time expires and polling stops (PV is now 74.3).
  9. Fifty-nine minutes later at 11:00 A.M., the hourly trend request restarts the trending process and reads the last stored PV (74.3).
  10. Polling begins and the Temporary Status Item Expiration Timer starts.
  11. Polling acquires the point’s current value and stores it as the update value of 76.5. At this point, the trend has a value of 74.3 with a timestamp of 11:00 A.M., even though the actual field value is 76.5.
  12. Sixty seconds later at 11:01 A.M., the Temporary Status Item Expiration Timer expires and polling stops (PV is now 76.7).

The process continues for the duration the trend settings dictate.