The development of a passive, wireless sensor system

<p>This thesis describes the development of a prototype passive, wireless sensor system based on magnetoelastic sensor technology. The application of the sensor system is aimed at the measurement of humidity levels in sealed containers and structures, in particular the detection of moisture ingress in building structures. The system uses magnetoelastic sensor elements as is commonly used in commercial electronic article surveillance (EAS) systems for the prevention of shoplifting. Magnetoelastic Metglas® 2826MB material is evaluated and it is shown that the application of a magnetic bias field of the appropriate magnitude is critical for optimum sensor performance. The sensors can be activated for the detection of water vapour by the application of an appropriate chemical interface layer. A polyvinyl alcohol (PVA) layer was found to produce a resonant frequency response of approximately 50 Hz/RH(%). The design and construction of a portable electronic sensor reader is described and it is shown that the reader can successfully interrogate the sensor inside sealed spaces at practical distances. The construction of a practical humidity sensor using a PVA coating and the humidity response of the sensor system is then calibrated using a commercial humidity sensor. The system showed good response over the 0-100 % relative humidity range, with some non-linearity observed at high humidity levels. The completed sensor system was then evaluated for practical applications including measurements inside a sealed food container as well as inside a wall cavity. The results indicated that the constructed system was capable of measuring humidity with reasonable accuracy in such applications.</p>

The development of a passive, wireless sensor system

<p>This thesis describes the development of a prototype passive, wireless sensor system based on magnetoelastic sensor technology. The application of the sensor system is aimed at the measurement of humidity levels in sealed containers and structures, in particular the detection of moisture ingress in building structures. The system uses magnetoelastic sensor elements as is commonly used in commercial electronic article surveillance (EAS) systems for the prevention of shoplifting. Magnetoelastic Metglas® 2826MB material is evaluated and it is shown that the application of a magnetic bias field of the appropriate magnitude is critical for optimum sensor performance. The sensors can be activated for the detection of water vapour by the application of an appropriate chemical interface layer. A polyvinyl alcohol (PVA) layer was found to produce a resonant frequency response of approximately 50 Hz/RH(%). The design and construction of a portable electronic sensor reader is described and it is shown that the reader can successfully interrogate the sensor inside sealed spaces at practical distances. The construction of a practical humidity sensor using a PVA coating and the humidity response of the sensor system is then calibrated using a commercial humidity sensor. The system showed good response over the 0-100 % relative humidity range, with some non-linearity observed at high humidity levels. The completed sensor system was then evaluated for practical applications including measurements inside a sealed food container as well as inside a wall cavity. The results indicated that the constructed system was capable of measuring humidity with reasonable accuracy in such applications.</p>

ABOUT ONE METHOD OF IMPROVING THE STATIC CHARACTERISTIC MAGNETOELASTIC SENSORS

The article is devoted to improving the static characteristics of magnetoelastic sensors. Using the energyinformational method, techniques for improving the static characteristic are identified. By implementing these techniques, the design of a magnetoelastic sensor is proposed. The design scheme of the proposed magnetoelastic sensor, the electrical connection diagram of the sections of the measuring windings and the principle of operation of the sensor are given. An expression of the static characteristic for estimating its degree of nonlinearity is obtained.

Magnetoelastic effect in axial stressed Ni-Zn ferrite material in Rayleigh region

The paper presents new and original results of investigation on magnetoelastic effect in Ni-Zn ferrite formed into ring core and subjected to the axial stress up to 20 MPa. The core was magnetized with relatively low magnetizing field, corresponding to the so-called Rayleigh region. The obtained results indicate, that there is a significant correlation between applied stress and magnetic properties of the material and the Ni-Zn ferrite can be utilized in development of magnetoelastic sensor of force and stress.