I noticed that the timestamp of the data stored in the public table varies every interval to the nanoseconds. Or is it milliseconds? So, for example, my scan rate is 1 second and I collect data once a second, but one example of my public table timestamps is as follows:
00:00:14.150
00:00:15.140
00:00:16.170
00:00:17.150
I'm not sure how big of an impact this is as far as whether by the time that the data is stored in the public table, the measurement has already been performed in that interval.
The reason why I ask this is that I store data in another data table with an interval of 1 second and in certain times some data fields stored in this one-second table and the same data fields stored in the public table differ, yet they are both "storing at the same interval" or close. So, basically for the same timestamp, one variable has one value in my one-second table and a different value in the public table. The one-second table timestamps every record at the top of the second, so that is why I bring the question of the timestamping of the public table.
Now, the problem that this brings is that when I'm validating my data, I have two tables showing the same seconds timestamp, but different values for the same variable.
Thanks!
I think you will find the Public table is generated on the fly by the logger when it is polled for by the PC. It gives the data at that instant in time, which could be with the logger being part way through executing a scan. As the polling of the PC will be a bit variable (as the PC has other things to do), the timestamp will jump around a bit at the millisecond level.
Data stored in a normal datatable holds the data relevant to when the datatable instruction is called in the program and the timestamp normally is the time at the start of the scan.
This will explain why you see those differences.
Andrew,
Thanks! This helps. I guess I should not be using the Public table for troubleshooting some of the values that I'm not saving in my other data tables.