Tuner

I am trying to use Talking Tuner to tune a harp. It is a very live instrument, and I think the tuner is picking up the harmonics when I pluck a string. The tuner is all over the place, way sharp, way flat, a little flat, ... despite my attempts to damp the other strings than the one I'm trying to tune.
Does anyone know how to make Talking Tuner less sensitive, or is there another accessible tuner that might behave better?
Thanks.