Segmented thermistors printed by NTC nanometric paste and applied in volume air-flow sensors

An investigation path starting from (Mn,Ni,Co,Fe)3O4 nanometric powder preparation, NTC thick-film characterization, realization and optimization of new planar thermistor geometries to custom design thermistors and their application for temperature and volume airflow sensors was recently determined. The aim was to make custom designed segmented NTC thermistors printed and sintered on alumina. Two types of volume airflow sensors were formed: indirectly heated and self-heated. A pair of segmented thermistors was placed in an air guide and connected to differential branches of the Wheatstone bridge. A heater was placed in the middle between the thermistors for the indirectly heated type, while for the self-heated type the same thermistors were self-heated by a constant current source. First the thermistor responses vs. the airflow (calibration curves) were measured, and then thermistor responses in time (inertia) to fast airflow changes from the minimum to the maximum. The results obtained could be applied in air conditioning for air guide flow regulation

Mn-Zn Ferrite Round Cable EMI Suppressor With Deep Grooves and a Secondary Short Circuit for Different Frequency Ranges

A novel Mn-Zn ferrite round cable electromagnetic interference (EMI) suppressor with deep grooves and a secondary short circuit was constructed, realized and measured. Three steps were passed in novel suppressor development: from developing a suitable magnetic material, to constructing a suppressor device, to forming a new class of possible applications. Soft ferrite feedstock was formed from fine commercial Mn-Zn powder and a Solvent system binder based mainly on wax. Cylinder-shape cores with grooves were injected by powder injection molding (PIM) technology, chemically and thermally debinded and sintered at optimal conditions (1280 degrees C/2 h). The samples were aimed to serve as cores for EMI suppressors on cables. Their impedance versus frequency was measured using the core length as a parameter. After that, copper wire was placed into the grooves on the outside surface of cores to form a secondary coil and different configurations were considered. The contribution of the short circuit coil inserted into the grooves to EMI suppression was measured and analyzed also. Maximal impedance values can be achieved with a secondary short circuited winding which passes through every groove. It was also shown that ferrite cores of the same length could be used for different frequency ranges by changing the configuration of secondary short circuited windings

Sintered strontium hexaferrite shaped by injection moulding in unidirectional magnetic and electromagnetic field

Strontium hexaferrite permanent magnets were produced by powder injection molding (PIM). The feedstock for powder injection molding was prepared by mixing strontium hexaferrite powder with a "Solvent system" organic binder. Injection was performed in the cylindrical cavity of the mold both for isotropic and anisotropic green samples. Diametrical alignment was attained using high energy permanent magnets embedded in the mold (unidirectional magnetic field), while axial magnetic alignment was done by DC current passing through a solenoid placed around the cavity (electromagnetic field). Green samples (with and without magnetic alignment) were subjected to solvent debinding and subsequent thermal debinding followed by sintering. Sintering conditions were optimized in order to achieve maximum energy product. Magneto-crystalline aligning in strontium hexaferrite was studied on both green and sintered samples using X-ray diffraction, scanning electron microscopy (SEM) and magnetic measurements (hysteresisgraphs). All measurements were made in the direction parallel to the aligning magnetic field. The obtained results confirmed a high degree of magneto-crystalline alignment

Analysis of a Mn-Zn Ferrite Bundle EMI Suppressor Using Different Suppressing Principles and Configurations

A novel round cable electromagnetic interference (EMI) suppressor comprising a bundle of Mn-Zn ferrite tubes was realized using different principles of suppressing, such as direct suppressing, inverting/suppressing, transform/inverting suppressing, and transform/short circuited secondary suppressing. Different primary to secondary configurations were realized for each suppressing principle and characterized in the EMI frequency region. The results obtained for different bundle configurations were compared with known commercial round cable ferrite suppressors and the initial bundle configuration made of a half turn wire through the central ferrite tube of the bundle. The results obtained for different principles and configurations were correlated in order to optimize the electromagnetic coupling between primary and secondary circuits. The values such as maximums of impedance Z(m), frequency of maximum impedance F-m and suppressing range Delta(f) around F-m calculated on 0.707 Z(m) were defined as the main parameters for each configuration. Certain correlations were noticed between impedance Z(m) and frequency F-m changes. Finally, the realized configurations were considered as devices suitable for EMI suppressing applications

Photoacoustic investigations of thermal and electronic properties of single crystal Ge doped with Cr

A high purity single crystal Ge with a (1 1 1) orientation was doped with Cr. A thin film of Cr was evaporated and then diffused into Ge substrate. The photoacoustic PA amplitude and phase spectra were measured and numerically analyzed. The substitution of Cr in Ge produces a compensation effect