Bad values in tag history

Sometimes I have bad values stores in MySQL and I don’t know how I got it… … 4cbd8c.jpg

  1. How can I know why it happens?
  2. How to delete this bad values from tag history?
  3. How to limit records if I got values like this?

What’s bad about them? They are very close to zero, but otherwise valid floating point values.

The can’t be so low or so high…
Should be from 0 to 10000.

Floating point values can have round-off issues – unavoidably. The number you circled is -0.0000000006959. That’s zero for most purposes. Add deliberate rounding (in the PLC, probably) to the appropriate number of decimal places if that’s a problem.

But how to delete these values?