Precision measurement of feebly magnetic materials
PFMM 비자성체 투자율 시험기
The model PFMM (Permeameter for Feebly Magnetic Materials) is an instrument to verify that a nonmagnetic
material (for example austenitic stainless steel) is really “non-magnetic”. The permeameter
PFMM quantifies the magnetic “weakness” of the material by measuring its magnetization curve,
relative permeability μr and susceptibility χ. When a non-magnetic material is used in an application
where the interaction with magnetic fields must be very low, the control of its magnetization and
permeability is fundamental. The permeameter PFMM measures the relative permeability in the
range between 1.001 and 4, with a typical total accuracy less than ±2%. When low values of
permeability and susceptibility are required, the Laboratorio Elettrofisico PFMM is necessary tool.
The sensitivity of the coil must be very high: for example, the PFMM can accurately measure the
susceptibility of good stainless up to 108 times lower than the susceptibility of a typical Fe-Ni, that
can be measured with a permeameter for ferromagnetic materials.
The permeameter PFMM meets the ASTM A342, A342M Standard.
Principles of operation
The Laboratorio Elettrofisico PFMM is based on the measurement of the magnetic polarization J
of the material under an increasing external field H. The ratio between J and H provides the
susceptibility χ and relative permeability μr = 1 + χ. The accurate measurement of J it is critical:
for example, for a material with μr = 1.001, applying a field H of 10000 gauss, the polarization J
will be 10 gauss only!
An extremely accurate compensation coil facilitates and performs automatically this measurement.
The sample must be in the shape of a bar with a uniform cross-section and be placed inside a
solenoid using a proper positioning tool (provided). The J field is measured with an inductive
sensor, while the H field is determined by the current through the solenoid. With the standard
diameter of the solenoid (Ø 50 mm), the length of the specimen must be greater than 100 mm
and the cross section not less than 20 mm2. The measurement of specimens that have different
dimensions is possible with custom solenoids and measuring sensors, that are available on request.
Turbo generators • Electron beam devices
NMR instrumentation Precision weights
Ionic devices
PFMM-03_제품카다로그.pdf
