  Mach-Zehnder interferometer, a powerful tool for a wide variety of
measurements, has been realized with Bose-Einstein condensates in recent
experiments. In this report, we propose and analyze a realizable scheme for
performing a Heisenberg-limited Mach-Zehnder interferometry with dipolar spin-1
condensate. Based upon adiabatic processes of sweeping the transverse magnetic
field, we demonstrate a perfect phase transition, which accomplishes the beam
splitter, phase shifter and recombiner as for a Mach-Zehnder interferometer.
The attractive dipolar interaction ensures the existence of a path-entangled
state which enhances the phase measurement precision to the Heisenberg limit.
We also discuss the spin-$1$ squeezing induced in the adiabatic passage and
show that the squeezing parameter attains its minimal value near the point of
saturation field.
