I have a problem with the ignition saving and loading data from plc tag:
I have 4 tags which receives temperatures from plc, each tag is saved by the historian,
the problem is that wrong data is saved when there is “jumps” in the temperatures,
for example: say that in 10:00:00 the temp in the first tag was 100 and it has not changed for 5 sec
and then the temp jumped to 200 in 10:00:05
if I try to pull the data between 10:00:00 to 10:00:05 the saved data will not be 100 but will be higher,
as the historian tries to “complete” the gap.
why does this happens, and is there any way to fix it?
There are two logging modes in Ignition. Are you using Analog or Discrete?
From your description, it sounds like you are using Analog because the Easy Chart is trying to interpolate the jump from one temperature to the other.
The way to “fix” it is to make the tag log in Discrete mode where the value is displayed constant between logged values. Think of it as using square wave forms to plot different points verses using a sloped line.
More information is here: https://docs.inductiveautomation.com/display/DOC79/Configuring+Tag+Historian#ConfiguringTagHistorian-ValueMode
Try to Synchronize Date Time of your DB and Ignition Gateway…maybe this will help