I’ve done the search and can’t find an answer so any help would be greatly appreciated. Is a “chromatic” tuner the best choice for a whistle? Thank you in advance.
Best always depends on the criteria no? But if it helps, that’s what I use to tune my whistles. You can blow notes sharp and flat too, so eventually the ear is used to play in tune.
C
I understand that a chromatic tuner can go farther than a normal guitar tuner which can only do those string notes. Is that true? Thank you.
Yes, a chromatic tuner lets you tune to any note. I’m pretty sure a guitar tuner is limited to the strings.
Jason
For playing a whistle, not so much. For building a whistle, sure.
Playing, typically you tune up to one note, such as A or G or D. If the whistle is in tune with itself, and your ear and breath control are good, the rest follows. For that, an A tuning fork works fine. Or a guitar tuner, which covers EADGB (though some guitar tuners may not respond well to the range of a high whistle). In a session, one of the instruments plays a reference note to tune to. If there’s a reliable fixed-pitch instrument like box or concertina, you often use that. If you’re playing with the Houston Symphony, you tune to the oboist’s A. 
Building, you of course want to check the intonation of every note, including possible cross-fingerings. A chromatic tuner lets you do that. A strobe (or pseudo-strobe) tuner is most precise, like the Peterson line. But other needle-type tuners work well. In sessions, I sometimes clip my Intelli tuner to the end of the whistle to tune. It looks funky.
A chromatic tuner also lets you practice your intonation while playing. But be aware, for both playing and building, that ITM is commonly played in just intonation, not equal temperament (12-TET). Only the more expensive chromatic tuners like Peterson, or software tuners, can be programmed for anything but 12-TET without manual calculation.
A good, free software-based chromatic tuner is the Shakuhachi tuner (Shaku8 or Tuner_E), available for download here:
http://www1.ocn.ne.jp/~tuner/tuner_e.html
Hope that helps!
John, you said that ITM is commonly played in JI. Does this refer mainly to melody instruments like flute, pipes, fiddle, whistle? Or does it include things like guitars, mandolins, guitars, accordions and the like, I had thought they were normally tuned to 12-TET?
Is is possible with a normal chromatic tuner to tune a whistle being made to JI by tunning individual notes to so many cents sharp or flat of the reading on the ET tuner? If it is possible then how could I find out what these settings would be for the D scale.
Thank you.
Thank you so much for your help. That shines a lot of light on the situation for me.