Voltage to frequency converter (VFC) is an oscillator whose frequency is linearly proportional to control voltage. The charge balanced VFC may be made in asynchronous or synchronous (clocked) forms. The synchronous charge balanced VFC or "sigma delta" (Σ-Δ) VFC (SVFC) is used when output pulses are synchronized to a clock. The charge balance VFC is more complex, more demanding in its supply voltage and current requirements, and more accurate. It is capable 16 to 18 bit linearity. The synchronous behaviour is good in many applications, but the output of SVFC is not a pure tone (plus harmonics) like a conventional VFC, but it contains components harmonically related to the clock frequency. In this paper, the new SVFC (NSVFC) is described. This NSVFC works similarly as conventional SVFC but it has a pure tone on output (for constant input voltage). Therefore, it is possible to measure the period of NSVFC output (this does not possible for SVFC).

In this paper some remarks about an innovative sensor for discrete distance measurement developed by the authors are discussed. The purpose of the proposed sensor is the measurement of remote target position independently on the property of the reflective surface. Application in the field of visually impaired people is in the large context getting serious advantage by the use of such apparatus. The possibility to obtain a low cost sensor device assuring the required performances is investigated. Nonlinear post-processing of the signals given by the sensor has been implemented improving the quality of the gathered information. Main features of the proposed system are its insensitivity to the target material and also to the influence parameters (e.g. light condition), high flexibility and reliability.

A transductor sensor of magnetic field intensity designed for use in a contactless transducer for measuring of heavy direct currents is presented. The sensor is built around a specially shaped and wound permalloy core and operates on the model of compensation arisen from the action of the magnetic field produced by the second harmonic of the magnetizing current.

Amorphous wires are relatively new materials exhibiting outstanding features that make them very suitable to be employed in sensors construction. In iron-rich magnetostrictive amorphous wires (MAW) several interesting effects occur, among which Matteucci effect is of particular relevance. This effect consists in generation of sharp pulses between the ends of a straight MAW when it is concomitantly subject to an axial alternative magnetic field and to a torsion strain. The pulses amplitude depends, among other factors, on the torsion angle. In the paper, the construction of such a sensor is presented, along with a method of signal conditioning designed to converting the peak amplitude of the sensor output pulses into frequency information. The conditioning section uses a loop that controls the magnetic field intensity through the current feeding a coil, considering as control parameter the pulses amplitude. The transducer performances were assessed in comparison with a circular encoder taken as reference. The experimental tests revealed good performances to the transducer, despite its low cost. An analysis of several external influence factors upon the transducer operation and characteristics is performed.

A novel RCE (Resonant-Cavity- Enhanced) HMSM (Heterostructure Metal-Semiconductor-Metal) hotodetector with AlGaAs distributed Bragg reflector is analyzed. The effect of the two dimensional electron gas (2DEG) in the GaAs absorption layer has been evaluated by comparing two samples, the first with a delta doped sheet in the upper AlGaAs layer, and the second with undoped AlGaAs. The I-V curve shows that there is a very low dark current (around 10 pA at high bias) and a value of 20 μA at high bias voltage in DC photocurrent, under 497 μW optical power laser illumination. C-V measurements highlight very low capacitance values, in agreement with the calculated geometrical ones. The photocurrent spectrum shows a clear peak at 850 nm wavelenght with full width at half maximum (FWHM) of around 30 nm, while time response measurement gives a 3 dB bandwidth of about 34 GHz. Combination of very low dark current and capacitance, fast response, wavelength selectivity, and compatibility with high electron mobility transistors makes this device especially suitable for short haul communications purposes.