This paper presents practical measurements of surface acoustic wave (SAW) velocity using phase technique. The two most important practical properties relating surface wave propagation on piezoelectric substrate are the wave velocity and electromechanical coupling coefficient. The main technique for obtaining precise results of SAW velocity is based on the use of laser probe method, which is expensive and complex. The presented method using phase technique is simple and accurate. The practical measurements are applied across the usable bandwidth of the SAW devices from 30 to 40 MHz, the used...
The use of the Allan variance for the characterization of the jitter timebase error in waveform digitizers is proposed. With this aim, the Allan variance is shown to be a sound basis for defining and measuring a suitable figure of merit, diagnosing the jitter noise type, and including a jitter error block into a previously proposed digitizer model. Experimental results highlighting the effectiveness of the Allan variance in the characterization of digitizer jitter error are discussed.
A method for characterizing Σ&Delta modulators is described which can be built in large integrated circuits or systems-on-chip. The method can be used to measure gain and phase, as well as, total harmonic distortion and signal to noise and harmonic distortion ratio parameters. It is prone to be built in circuit, when computational resources such as digital signal processors or re-programmable logic are available, but can also be used in computer simulations making it easier to compare expected with measured performances.
Conventional methods for correcting linearity errors in a digital to analogue converter (DAC) rely on characterising the DAC first. This paper describes a technique that can increase linearity without characterizing the DAC. It is in principle, able to remove completely deterministic errors. As no calibration is needed the improvement can track dynamically changing errors due for example to thermal effects.
A lot of geotechnical engineering problems can be analysed in situ with tests of horizontal and vertical loaded piles. These are required, for instance, to study the behaviour of piles isolated and in groups. Based on the emergent concept of "smart sensor" a unit was developed that converts the deformation of the concrete pile measured by an LVDT on digital information. This unit is integrated on a local area network supervised by a command unit located at the surface. The communication protocol is based on a master-slave structure supported by dedicated developed commands.
A fiber optic reflectometric temperature sensor was set up and characterised. Its reduced dimensions render it suitable for monitoring application whenever a high spatial resolution is required. The metrological performance of the first prototype seems very interesting in terms of accuracy and above all, response time. This performance will be further improved by employing a side-polishing technique for sensor realisation and silver mirroring for its reflective part.
This paper describes test procedures to characterize the behavior of logarithmic analog-to-digital converters. Logarithmic A/D converters are usually characterized in terms of signal-to-noise ratio (SNR) or in deviation of the ideal characteristic in dB. There are a lack of test methods definition in the literature, as can be observed in the IEEE standard 1241 for these type of converters. Systematic test procedures have been applied to µ-law converters according to the G.711 standard, and to a new type of high-speed true logarithmic pipeline A/D converter. DNL and INL had been defined in...
In this paper it is proposed a solution for the numerical linearisation of non-linear parameter dependent sensors. The sensor data-processing architecture combines non-linear analogue to digital conversion with intelligent data processing based on an artificial neural network both implemented using a microcontroller. An application of the processing architecture to gas and vapour concentration measurement is reported.
A prototype of humidity sensor, based on a solgel ceramic compound of phosphorous pentoxide P2O5 and silica SiO2, is presented. The sensing principle is based on the high affinity between phosphorous pentoxide and water: the frequency spectrum of the electrical impedance varies according to humidity with remarkable sensitivity. The silica basis allows the sensing element to be deposed on a oxidized silicon chip substrate for microsensor applications. The sol-gel production allows the sensing element to be easily developed as thin-film for fast time response. Design criteria and preparation...
The purpose of this paper is to provide robust experimental validations of timing jitter measurements and to derive some applications in the field of Analog-to-Digital Converter (ADC) characterisation. The timing jitter measurements are obtained by use of a recently proposed method, which is based on the use of two ADCs driven by the same input and clock signals.