I have NEVER used an electronic tuner myself when playing the violin and additionally, I was fortunate that when I started learning to play the violin there were no such things as electronic tuners anyway! Accurate relative pitch was something that I didn't have a problem developing and to me,
all pianos sound out of tune regardless - equal temperament thing I guess.
The only time I've ever used an electronic tuner is when checking the intonation of an oboe, or oboe reeds just to see what note the reed crows at. If it's crowing at Bb, then for me I know the reed will be ok.
I have however, carried an electronic tuner in my violin case just to prove to some of my pupils
how bad their intonation is, especially those who swear blind that they are listening to ever note they play.
Using open strings (as a double-stop drone) when playing scales is a very good way to improve relative pitch. It encourages the ear to really listen to the interval being created - something which can present a problem when pupils first learn to double stop, trying to place their fingers where they think the notes will be rather than listening to and forming the interval by ear.
I know there will be those who disagree, but I find the most problematic pupils with tuning on the violin are those who've learnt to play the piano first.
Every single one of them insists on looking at the keyboard for help when naming key signatures, tones or semi-tones and even playing a scale. GRRRRR! it really gets on my wick...

The first thing I do in their lessons is shut the blasted lid over the keyboard!