I use a beam scale (RCBS, what I have, not saying it's the best) to randomly check even my Hornady electronic powder measure/scale unit.
Electric stuff is electric stuff and sometimes electric stuff does funny things you don't realize or want it to do. So I check every so often with the beam scale to insure nothing is drifting high/low on the electronic unit.
A good beam scale is darn quick. Smooth movement, magnetic dampening means it settles very quickly.