Piston guide and magnet assembly for the KRISS watt balance

The piston guide and magnet assembly for the KRISS watt balance were tested. The velocity of the piston guide was controlled within 4×10
^-3
at the velocity of 2 mm s
^-1
using a linear motor and linear encoder feedback. The magnet assembly which consists of two permanent magnet rings and closed yokes was fabricated. B-field at the air gap of 25 mm was measured using a Hall probe. The B-field uniformity was within 5×10
^-4
over the vertical distance of 24 mm.