A Measurement System for On-line Estimation of Weed Coverage

This paper describes two different solutions for the estimation of weed coverage. Both measuring systems discriminate the weed from the ground by means of the color difference between the weed and ground and can be used to on-line control tractor sprayers in order to reduce weedkiller use. The solutions differ with respect to the sensor type: one solution is based on a digital camera and a computer that analyzes the images and determines the weed amount, while the other simpler solution makes use of two photo detectors and an analog processing system. The camera-based solution provides an uncertainty of a few percentage, while the photo detector-based one, though extremely cheap, has an uncertainty of about 5% and suffers from changes in light conditions, which can alter the estimation

An Ultrasonic Sensor for Distance Measurement in Automotive Applications

This paper describes an ultrasonic sensor that is able to measure the distance from the ground of selected points of a motor vehicle. The sensor is based on the measurement of the time of flight of an ultrasonic pulse, which is reflected by the ground. A constrained optimization technique is employed to obtain reflected pulses that are easily detectable by means of a threshold comparator. Such a technique, which takes the frequency response of the ultrasonic transducers into account, allows a sub-wavelength detection to be obtained. Experimental tests, performed with a 40 kHz piezoelectric-transducer based sensor, showed a standard uncertainty of 1 mm at rest or at low speeds; the sensor still works at speeds of up to 30 m/s, although at higher uncertainty. The sensor is composed of only low cost components, thus being apt for first car equipment in many cases, and is able to self-adapt to different conditions in order to give the best result

Power meter for Highly-Distorted Three-Phase Systems

This paper describes a low-cost, three-phase power meter, which is based on a fast, specially designed acquisition board coupled to a PC via the PC parallel/printer port or by means of an AT card. The power associated with the fundamental and first harmonics is computed by software that operates in the time domain and employs a sample-weighting procedure that makes the uncertainty related to the asynchronous sampling negligible. The low-cost acquisition board features two 8-bit 1 MHz converters and a local RAM, which decouples the PC clock from the measurement requirements. Hall effect transducers are used for the current channels and fast differential amplifiers for the voltage channels. The fast sampling frequency allows simple antialiasing filters to be employed. Digital filtering is used to reduce the sample number while increasing the resolution. The power uncertainty provided by this arrangement is less then 0.1 % with 2.5 measurements per second when a low-cost 486DX33-based PC is use

Noninvasive Solution for Electrochemical Impedance Spectroscopy on Metallic Works of Art

Metallic works of art of cultural relevance are continuously subjected to corrosion as the environment becomes increasingly polluted. A fast and simple method to in situ assess the conservation conditions is therefore required. This paper describes the development and performance of dry and gel-based electrodes which can be used to assess the surface conservation state without the need to move the artifacts and which do not cause any damage to them. The electrodes can be used with a portable electrochemical impedance spectroscopy system, without employing electrochemical cells. The proposed solution does not provide all the information that one can obtain using an electrochemical cell, but it can discriminate between protective coatings. It can be used to assess the protective capability of corrosion product layers and natural patinas, and it can therefore enable a noninvasive routine surface assessment to be conducted that could be extremely useful for people working in the field of conservation of cultural heritag

Low-Cost Laser-Based Localization System for Agricultural Machines

This paper describes the design and test of a low-cost localization system for agricultural applications, which determines a tractor position in fields up to 0.5 km with an uncertainty of about 1 m. The proposed system employs a standard unmodified laser head, which is commonly used for field leveling, plus a reference ground-fixed laser receiver and requires neither laser modulation nor expensive time-of-flight measurements of light beam

Uncertainty Analysis of Feature Extraction from Expired Gas Traces

Noninvasive medical analyses are a convenient method to study several pathologies even though their indirect nature often requires a complex processing to determine the relevant health "indicators". The usefulness of such indicators depends on the employed model, but also on the uncertainty that is connected to the complex processing involved in the indicator determination. This paper deals with the problems related to the estimation of the uncertainty when the indicators are computed by means of a nontrivial processing on recorded traces of clinical parameters. The paper is focused on the analysis of expired gas traces, but the procedure can also be applied to many other cases where the processing involves manual or automatic selection of suitable "key points" on repetitive traces

Measurement Procedures for the Electrical Characterization of Oxide Thin Films

This paper describes a measurement system for the electrical characterization of oxide thin films. Such films can be produced using plasma-sputtering processes and permit the realization of a large set of high-performance components, such as capacitors, active devices, sensors, and protective coatings. The electrical properties of the oxide films, which have a thickness of less than 1 μm, are difficult to measure since very high resistances (on the order of gigaohms) and small capacitances (on the order of picofarads) are expected for contact areas smaller than 1 mm2. The measurement system and the procedures described in this paper represent an alternative solution to the commercial devices, which usually employ a mercury probe for performing the contact with the specimen under characterization. Furthermore, the proposed system can be used not only to estimate the electrical properties of a single point but to evaluate the uniformity of oxide films on large specimens as well. The experimental results reported refer to valve-metal-based oxide films deposited in a lab-scale capacitively coupled parallel-plate reactor and show the effectiveness of the proposed procedure

A Traveling Standard for the Calibration of Data Acquisition Boards

The large use of measurement systems based on data acquisition boards makes the traceability-chain assurance a tricky problem due to the difficulty in consistently calibrating such boards. In this paper, the authors describe a traveling standard which can be used for the calibration of many commercially available acquisition boards. By employing such a traveling standard, the calibration procedure can be remotely exercised by a calibration laboratory through the personal computer which hosts the board that has to be calibrated. In such a way, the calibration results refer to environmental, software, and hardware conditions that exactly match the board-operating conditions. Furthermore, the board unavailability time is drastically reduced, with a consequent economic advantage for the board owner. The traveling standard is based on a microcontroller which is responsible for the communication with the PC that hosts the board and for the board-stimulus generation, and on a digital multimeter, which acts as a reference standard

A Microwave System for Relative Humidity Measurement

This paper deals with a microwave hygrometer that is based on the sensitivity of air permettivity to humidity. The hygrometer embeds a microwave generator which feeds two different channels. A channel is a holed waveguide, whose permettivity depends on the air humidity, while the other channel is insensitive to the air humidity. The output signals of the two channels are suitably combined in order to obtain the corresponding phase angle, which depends on the permettivity of the air inside the holed waveguide and therefore on the air humidity. Two possible implementations of the proposed principle are described which permit one to obtain an uncertainty of a few percentage of relative humidity in the humidity range of 10% RH to 90% RH and in the temperature range of 5 °C to 40 °C, but with different costs and complexities. The main characteristics of the proposed sensor are a fast response, a low sensitivity with respect to air pollution and the absence of hysteresis phenomena

A Wireless Sensor Network for Cold-Chain Monitoring

This paper deals with a wireless sensor network that was specifically designed to monitor temperature-sensitive products during their distribution with the aim of conforming to the cold-chain assurance requirements. The measurement problems and the constraints that have been encountered in this application are initially highlighted, and then, an architecture that takes such problems into account is proposed. The proposed architecture is based on specifically designed measuring nodes that are inserted into the products to identify their behavior under real operating conditions, e.g., during a typical distribution. Such product nodes communicate through a wireless channel with a base station, which collects and processes the data sent by all the nodes. A peculiarity of the product nodes is the low cost, which allows the information on the cold-chain integrity to be provided to the final customer. The results that refer to the functional tests of the proposed system and to the experimental tests performed on a refrigerated vehicle during a distribution are reporte