also:
a. you may need to attach the thermometer to something denser (I used a ring spanner) in order to swing it fast enough (overcoming air resistance). If so, think strong string attached to the spanner or whatever
b. the pseudo force is proportional to radius x angular velocity squared so that's another reason for outside (unless you have a big house)
c. some recommend practising with a cat.
-- Robin reply-to address is (intended to be) valid