Microprocessor-based Data Acquisition System Research Articles

Minimizing Error in the Analog Channel of a Geophysical Data-Acquisition System

The possible exclusion from processing of measurement data associated with errors owing to zero bias instability (temperature drift) and to the spread in the transfer coefficient in the analog channels of microprocessor-based data acquisition systems is demonstrated.

Experimental Vibration Analysis of a Cracked Laminated Glass Beam with Bolted Joint

In this study, in order to determine the very early load transfer behavior in the bolted joint connection, experimental dynamic analysis of different laminated glass beams including two surface cracks is considered. For this purpose, both three different plastic interlayers (i.e., three types of polyvinyl butyral—PVB) and three different glass-lamina thicknesses are taken into account. Effects of the plastic interlayer, thickness of the glass-lamina, number of surface cracks and their locations on the vibration characteristics/structural performances are examined experimentally. Vibration tests are performed to present free vibration characteristics of the laminated glass beams under clamped-free boundary conditions. Experimental dynamic analysis consists of six parts: (I) vibration analysis with no-crack and no-hole with a bolted joint; (II) vibration analysis with a surface crack and no-hole with a bolted joint; (III) vibration analysis with two surface cracks and no-hole with a bolted joint; (IV) vibration analysis with no-crack and a hole with a bolted joint; (V) vibration analysis with a surface crack and a hole with a bolted joint; (VI) vibration analysis with two surface cracks and a hole with a bolted joint. For these experimental steps, an impact hammer with a force transducer is used to excite the uncracked or cracked composite beams through the selected points. After the excitation, the responses are obtained by an accelerometer. The vibration measurements are completed using a microprocessor-based data acquisition system and nCode GlyphWorks software. Results are given in tabular and graphical forms.

Wearable acceleration sensor application in unilateral trans-tibial amputation prostheses

The availability of human walking gait data collected from the wearable acceleration sensors for trajectory control of an active artificial ankle joint in the unilateral trans-tibial prosthesis was investigated in this study. It is observed that the collected acceleration data can be used in the rulebased control of the prosthetic leg. A portable microprocessor-based data acquisition system, and data transfer module were designed for capturing the acceleration signals during walking. Flexionextension angle pattern of ankle joint was determined from acceleration signals of two tri-axial wearable accelerometers placed on the shank and foot segments. This pattern was utilized for control of the active artificial ankle joint in the trans-tibial prosthesis. This approach may have the potential of contributing the development of better prostheses.

Comparison of Energy and Exergy Efficiency of Community and Domestic Type Parabolic Solar Cookers

The work presented in this article essentially consists of evaluating the energy and exergy efficiency of two types of parabolic solar cookers. The experiments on both the cookers were performed in summer and winter, both in the climatic conditions in India. The measurements were done by using a microprocessor-based on-line data acquisition system using class I solar pyranometer and Pt. 100 temperature sensors. The energy end exergy efficiencies of both the cookers were experimentally evaluated. The energy output of the community solar cooker varied between 2.73 to 43.3 W and 7.77 W to 33.4 W for the domestic solar cooker. The exergy output for community solar cooker was in the range of 1.92 to 2.58 W, whereas for the domestic solar cooker, it varied from 0.65 to 1.45 W. The energy efficiency of the community solar cooker varied from 8.3% to 10.5% and for the domestic solar cooker, it varied from 7.1% to 14.0%.

An active drop counting device using condenser microphone for superheated emulsion detector

An active device for superheated emulsion detector is described. A capacitive diaphragm sensor or condenser microphone is used to convert the acoustic pulse of drop nucleation to electrical signal. An active peak detector is included in the circuit to avoid multiple triggering of the counter. The counts are finally recorded by a microprocessor based data acquisition system. Genuine triggers, missed by the sensor, were studied using a simulated clock pulse. The neutron energy spectrum of (252)Cf fission neutron source was measured using the device with R114 as the sensitive liquid and compared with the calculated fission neutron energy spectrum of (252)Cf. Frequency analysis of the detected signals was also carried out.

A new experimental setup to study UHE cosmic ray based on measurement of arrival time spread of secondary particles from EAS

A new experimental setup has been developed in the Mini Array Research Laboratory, Gauhati University to study UHE Cosmic rays by measuring the arrival time spread of the secondary particles from Extensive Air Showers (EAS) produced by primary particles of energy ≥10 15 eV. The setup consists of fast timing detectors, necessary electronics and microprocessor based data acquisition system. In this paper we discuss details about the hardware and software aspect of the experimental setup.

Disturbance recorders trigger detection and protection

The ability to perform power system measurements synchronously over large areas opens a new window on dynamics occurring within the power system. A number of events were recorded by GPS satellite-locked disturbance recorders, and the records illustrate the frequency variation that exists across a network during transients, the swinging of various points in the system with respect to each other during a disturbance, and the effects of loss of generation or load over extremely long distances. Measurements are made possible by the use of embedded computers and digital signal processing technology. The author discusses the use of phasor measurement unit, a microprocessor based data acquisition system and signal processing platform with an integral GPS clock and multiple inputs. The system allows more accurate recording of power system phenomena that would otherwise remain undetected. System response data permits the validation of models, real-time measurement of protection characteristics, and early detection of potential system instabilities or equipment malfunction.

In vivo liver differentiation by ultrasound using an artificial neural network.

A pattern recognition algorithm and instrumentation for in vivo ultrasound human liver differentiation are presented. An available 16-MHz microprocessor-based data acquisition and analysis system with 6-bit resolution is used to capture, digitize, and store the backscattered ultrasound signal. The algorithm is based on a multilayer perception neural network using the backpropagation training procedure. The network is implemented to differentiate between normal and abnormal liver. Data earlier obtained from 18 volunteers with normal liver history and from 12 volunteers with liver abnormalities are used to test the algorithm. The power spectra of the backscattered signal from depths of 5, 6.5, and 8 cm in the liver are calculated. The acoustic attenuation coefficient is calculated by the log spectral difference technique over the frequency range from 1.5 to 4.5 MHz. The change of speed of sound with frequency (dispersion) is estimated over the 3-MHz bandwidth. The attenuation and velocity dispersion are used as differentiation features. The results show that of the 22 tested cases, the system differentiated correctly 19 and 20 cases when using the attenuation and the velocity dispersion, respectively. The average magnitude of dispersion of liver is estimated to be 1.67 +/- 0.1 m/s/MHz and about 2.3 +/- 0.18 m/s/MHz in the normal and abnormal cases, respectively. The overall performance of the system for liver differentiation is 91% for normal cases, and 86% for abnormal cases. The data files are also differentiated using the nearest neighbor statistical classifier. The results show that of the 30 tested cases, 23 files are differentiated correctly using the attenuation coefficient.

A setup for determination of EAS parameters

A new experimental setup has been developed at the Cosmic Ray Research Laboratory of Gauhati University to study the complex characteristics of large extensive air showers. The system consists of particle detectors, Cherenkov light detectors, radio pulse detector, necessary electronics and microprocessor based data acquisition system. The versatility of this setup has been described in this paper.

Real-time measurement of the contribution of the muscular activity to the metabolic rate in freely moving rats

A new real-time ergometric system, ERGORAT, for measuring the energy expenditure due to muscular activity of small mammals is described. The method is based on measuring the vibrations induced by a freely moving rat to a platform on which it is living. Six accelerometers placed on the platform detect all the vibrations produced by the rat. The co-ordinates of the centre of mass of the animal are located by an optoelectronic device. This location and the six accelerations are fed to a microprocessor-based data acquisition and processing system. Using a Lagrangian dynamic model, the values of the mechanical energy transferred to the platform are computed every second. ERGORAT is used as part of an experimental setup allowing the measurement of the energetic balance of lean and obese rats. The results clearly show that the increase in metabolic rate of obese rats during cold exposure can be entirely explained by the cost of their increase in locomotor activity, whereas for lean rats, this cost accounts for only 41.5 per cent of their metabolic increase, the remaining being the contribution of their active brown adipose tissue.

Microprocessor-based Data Acquisition System for Measuring Soil Moisture and Temperature

A microprocessor-based data acquisition system for measuring soil moisture and temperature was developed. The battery-powered system, consisting of a datalogger, multiplexer circuit, and interface circuit, was tested with three types of sensors: tensiometer-mounted pressure transducers, resistance-type moisture blocks, and thermocouples. Readings from the different sensors were not adversely affected by either the multiplexer or interface circuitry, except when reading small resistances, encountered when using moisture blocks in high moisture conditions. There was excellent agreement between datalogger measurements read through the system and those read either manually or directly connected to the datalogger for input confirmation.

A decision table and rule based interpretation system for epileptic discharges.

The representation of the various features of waveforms and their correlations, in EEG recording for the diagnosis of different diseases have been carried out by many researchers due to the impact of knowledge based on expert systems development tools and techniques. The realisation of these system requires a specific hardware and software tool for its implementation, which may be a costly affair. The design and development of low cost effective system for the diagnosis of epileptic patients have been reported in this paper. Two different and linked (at certain stage) approaches (i) decision table; (ii) rule based system have been followed to model the reasoning processes of physician in the diagnosis. In the decision table the features of specific waveforms of EEG are represented in the tabular form. The features are obtained from a 8086 microprocessor based data acquisition system. The rule based system is designed with IF and THEN form of rules using Turbo-Prolog as programming language tool and is implemented on low cost PC-AT. The results obtained are at an intermediate stage of data processing by decision tables and at the final stage being carried out by rule based model. The performance of the system is evaluated by recording of EEG of some epileptic patients. The results obtained are comparable and to a certain extend appreciable in the opinion of the physician.

Analysis of human muscle contractility with a microcomputer-controlled stimulus and data acquisition system.

This report describes and assesses a technique to indirectly stimulate and quantify the human in vivo muscle response for clinical use. A method has been developed to isolate, stimulate, and record the flexor function of the first dorsal interosseus and first volar interosseus at the metacarpophalangeal (MCP) joint by stimulation of the ulnar nerve at the wrist. A microprocessor-based data acquisition and analysis system was built to deliver the electric stimulus and convert the muscle action potential (M-wave) and force measurements into digital form for analysis. To evaluate the technique, the twitch, paired twitch, and tetanic contractions were analyzed in 81 normal subjects. The tension developed by the youngest subjects (14 to 19 years old) was significantly less than the tension developed by subjects in the three older groups (20 to 34 years, 35 to 50 years, and 50 to 65 years); the tensions in the older groups were not significantly different from each other. Only minor gender differences were noted. This indicates that it is necessary to use age-group controls when looking for evidence of a muscle contractile abnormality in patients with neuromuscular disorders. posttetanic potentiation of the twitch was observed in all healthy subjects, and there was no evidence of an age or gender influence. The posttetanic increase in twitch tension was not associated with a prolongation of the twitch contraction time.

A portable insole plantar pressure measurement system

To analyze plantar pressures during activities of daily living, one needs a fully portable system capable of measuring many steps over extended periods. This paper presents an inexpensive, reliable, portable plantar pressure acquisition system which we have developed. It allows the long-term recording (up to 2 hours) of pressure-time data from 14 pressure sensors within insoles. The sensor chosen is an inexpensive, conductive polymer sensor that is only 0.25 mm thick yet able to withstand sudden overloads. The portable, battery-powered, microprocessor-based data acquisition system has a memory space of 480 kbytes for data storage. It can collect pressure data from 14 insole sensors at a 20 Hz sample frequency for 5 seconds every minute over a 2-hour period. It enables the long-term measurement of plantar pressures during normal activities in a natural unrestricted environment. The design and development of this portable insole plantar pressure measurement system is described.

Improved microprocessor based data acquisition system for Mössbauer spectroscopy

A low cost data acquisition system for Mössbauer spectroscopy based on a microprocessor development system with a low dead time of the order of 0.16 μs per channel is discussed here.

A microprocessor-based data-acquisition system for measuring plantar pressures from ambulatory subjects

We have developed a portable microprocessor-based data-acquisition system to measure discrete plantar pressures within the shoe from ambulatory subjects. The system offers improved accuracy, repeatability, portability, and flexibility not available in current commercial systems. It consists of 14 conductive polymer pressure sensors, 14 analog amplifiers, an 8-bit analog-to-digital converter, a microprocessor, 120 kbytes of memory space, and a parallel I/O interface. Seven pressure sensors are embedded within each insole and located at the posterior heel, anterior heel, the four metatarsal heads, and hallux of each foot. The system is capable of continuously sampling 14 channels of pressure data for 7 min at a 20-Hz sample rate. The recorded data are downloaded into a microcomputer for further processing, analysis, and display. Foot pressures have been acquired from a sensate subject during multiple walking trials.

Microprocessor-based diagnostic X-ray beam quality assurance dosimeter using a photovoltaic detector/amplifier device

A novel instrument for non-invasive testing and quality assurance of diagnostic x-ray units, using a photovoltaic detector/amplifier device as a dosimeter is described. This small-size, fast, low power transducer has a uniform stable response (within ± 6%) of 3.7 V/(cGy min −1, air kerma rate) for 50–150 kV lightly filtered x-rays. A microprocessor based data acquisition system samples the x-ray intensities with an unshielded detector, or their ratio, with a pair of detectors shielded by differential filters and stores these data in memory; then evaluates and displays kVp, exposure time (number of x-ray pulses), beam output and waveform.

A microprocessor-based semiconductor solar radiometer

The photocurrent produced by a silicon PN junction is used as a solar radiation transducer. It has high and linear sensitivity in the main part of open sunlight spectrum. Using a commerical device as sensor, a low-cost solar radiometer can be constructed. The photocurrent produced is electronically tailored to store solar radiation data in a microprocessor-based data acquisition system. This portable instrument can be used in remote sites and substitutes solar monitor, integrator and data-logger equipment. The data can be transported by a RS-232 port or in a nonvolatile static RAM card, interfaceable with personal microcomputer.

Automated analysis of prerecorded evoked electromyographic activity from rat muscle

An automated microprocessor-based data acquisition and analysis system has been developed specifically to quantify electromyographic (EMG) activity induced by the convulsant agent catechol in the anaesthetized rat. The stimulus and EMG response are recorded on magnetic tape. On playback, the stimulus triggers a digital oscilloscope and, via interface circuitry, a BBC B microcomputer. The myoelectric activity is digitized by the oscilloscope before being transferred under computer control via a RS232 link to the microcomputer. This system overcomes the problems of dealing with signals of variable latency and allows quantification of latency, amplitude, area and frequency of occurrence of specific components within the signal. The captured data can be used to generate either signal or superimposed high resolution graphic reproductions of the original waveforms. Although this system has been designed for a specific application, it could easily be modified to allow analysis of any complex waveform.

The effect of increased transpiration on photosynthesis of corn part I. A field portable single plant enclosure system

A climate-controlled, field-portable, single-plant enclosure system is described. The system is capable of measuring the photosynthesis (PS) and transpiration (TS) of a single corn plant on a half-hourly basis to better than ±5% of typical PS values and ±16% of typical TS values. All data acquisition and climate control is aided by a microprocessor-based data acquisition system. Humidity is controlled and TS measured by absorbing transpired water on a column of CaSO 4; PS is obtained from required CO 2 injection rates. Both water vapour and CO 2 concentrations are kept constant and air temperature is maintained close to ambient by a water-to-air heat exchange system. At present, the system is capable of controlling to constant, user-selected CO 2 and water vapour concentrations. The system could be easily modified to study the effects of elevated CO 2 concentrations, levels of various pollutants, changes in air temperature, PPFD, and many other environmental variables.