  We demonstrate simultaneous measurements of DC transport properties and flux
noise of a hybrid superconducting magnetometer based on the proximity effect
(superconducting quantum interference proximity transistor, SQUIPT). The noise
is probed by a cryogenic amplifier operating in the frequency range of a few
MHz. In our non-optimized device, we achieve minimum flux noise $\sim
4\;\mu\Phi_0/Hz^{1/2}$, set by the shot noise of the probe tunnel junction. The
flux noise performance can be improved by further optimization of the SQUIPT
parameters, primarily minimization of the proximity junction length and cross
section. Furthermore, the experiment demonstrates that the setup can be used to
investigate shot noise in other nonlinear devices with high impedance. This
technique opens the opportunity to measure sensitive magnetometers including
SQUIPT devices with very low dissipation.
