if it of any help to see one set up, here is my Korg AT1 clipped onto the 'harp. You can sorta see the lights and the needle and the general size...tuners DO come smaller these days, but you can't plug into all of 'em)

(Billy The Bus...yeah, a good ear is great, but both mine are 'average'..*grin*...I can't wait for a piano tuner, so I use Mr. Korg.....I have a t-shirt that says "I tune my autoharp every month or two--need it or not")