25-08-2023, 05:13 PM
(23-08-2023, 08:39 AM)ppppenguin Wrote: True RMS DMMs, such my Fluke 87, need to be treated with caution when measuring awkward waveforms. A notable recent case was checking the heater voltage on a video monitor. The heater supply was derived from the LOPT and gave daft readings on the 87..
That's probably the same effect I noted in an earlier post, it's really annoying and to my mind massively diminishes the usefulness of the meter!
(05-07-2023, 03:43 PM)Kalee20 Wrote: ... my 'true RMS' Fluke 177 isn't any good!
It filters out any DC and does a true RMS on the AC content only. That means if there's any DC component, such as a diode dropper, you won't get a true RMS on the whole - and your valves will overheat.
It's easy to see if this is the case. Just select AC, and measure a DC voltage or current, True 'true RMS' will give the DC value; AC-filtered 'true RMS' will show zero (after a brief reading).
