Fastest Logging Rate

Just wondering what is the fastest data logging rate to a DB that has been reliably used with Ignition?

For example could I use it to create a simple storge scope application to a Siemens PLC and log say every 10ms or is that beyond the capabilities of the software?

Without much special work or consideration, I don’t normally ever tell people less than 100ms. And when pressed, I wouldn’t claim that data could be directly logged faster than 50ms. HOWEVER… there are many things to consider, and these questions always require more careful analysis.

First, is the logging occurring constantly at 10ms? Is the data changing each cycle? When people ask “Can I log at 10 ms”, I think they usually refer to the resolution, and how quickly a particular change can be noticed. But without more details, we have to assume the worst, which means… 1 tag, changing every 10ms = 8640000 points a day, assuming 16 bytes in a transaction group table (int + overhead, though this would average down with more columns)= roughly 4gb /month. Through the tag history system, that’s like 10gb/month. Per tag. In reality, though, the actual changes may be happening much less frequently.

Aside from data size, there’s the question of how to get it in the db. As I mentioned, I start by saying “100ms”, and then maybe will go down to 50ms, depending on the situation. But that’s direct logging. If your application is such that the data doesn’t need to be constantly logged in real time, there are some things you can do. You can easily get 10ms resolution if you store buffers of data in the PLC, and then transfer them using something like a block group. For example, you could have three buffers that consist of 100 values (1 second of data). When one buffer is full, you set a trigger, and a corresponding group reads the values and stores them (and the plc starts storing to the next buffer, circling through). Depending on a few factors, that whole procedure could take between 20-100ms. Not bad.

Perhaps you didn’t want all of this info, but my main point is, there are different types of 10ms data :laughing: