As RMS and True RMS are ambiguous terms -- vendors using them to mean different things -- it is best to stay away from the term "True RMS" altogether, and communicate the device's capabilities in a more precise manner.
Therefore, all DMM drivers must be adapted to use mqflags as follows, according to the device specification:
1. Set only AC if the device assumes sinusoid AC voltages.
2. Set AC and RMS if the device can handle non-sinusoid AC voltages correctly
3. Set AC, DC and RMS if the device can handle non-sinusoid mixed-mode voltages correctly
This was already done for the Gossen Metrawatt driver by Matthias Heidbrink.