Data Clock Issues

Mate3 and Mate3s communications devices for Outback Power

Data Clock Issues

Postby intellact on Tue Nov 14, 2017 9:29 am

The precision and accuracy of a tool like WattPlot sometimes gets it into trouble when interfacing with real-world devices. :roll: Here's the latest example:

The MATE3 has a built-in data logger which can record system performance to the second. The CSV files that it produces include a time stamp for each second. So what does it mean when the data sequence goes like this:

~00:25
~00:26
~00:27
~00:28
~00:29
~00:30
~00:31
~00:26

~00:27
~00:28
~00:29
~00:30
~00:31
~00:32

How can time step backwards 5 seconds? :shock:

I have observed this phenomenon before, and WattPlot has long been programmed to catch these things, but it ends up ignoring the rest of the file as unreliable. (I have seen very rare instances where file contents appear to overlap with another file on the MATE3 SD card.)

Today, I think I figured out what might be happening. :-k

The MATE3 has the ability to resynch its clock with internet time. I don't know how often it does this, but if it were running fast by 5 seconds, it would explain the 'correction' seen in the data above.

I'm going to have to make WattPlot even smarter, yet again, to allow such corrections to be acceptable (given a 'reasonable' roll-back of time). The data will still be processed and accumulated, but it won't internally store the data that cannot be uniquely assigned to a specific second.

More work - the price to pay for precision and accuracy... <sigh>
Andrew Welch, creator of WattPlot
User avatar
intellact
OutBack Czar
 
Posts: 652
Joined: Mon Nov 28, 2005 4:20 am
Location: Ontario, Canada

Return to Mate3 / Mate3s

Who is online

Users browsing this forum: No registered users and 3 guests