Low-power direct resistive sensor-to-microcontroller interfaces

“© © 2016 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.”This paper analyzes the energy consumption of direct interface circuits where the data conversion of a resistive sensor is performed by a direct connection to a set of digital ports of a microcontroller (µC). The causes of energy consumption as well as their relation to the measurement specifications in terms of uncertainty are analyzed. This analysis yields a tradeoff between energy consumption and measurement uncertainty, which sets a design procedure focused on achieving the lowest energy consumption for a given uncertainty and a measuring range. Together with this analysis, a novel experimental setup is proposed that allows one to measure the µC’s timer quantization uncertainty. An application example is shown where the design procedure is applied. The experimental results fairly fit the theoretical analysis, yielding only 5 µJ to achieve nine effective number of bits (ENOB) in a measuring range from 1 to 1.38 k. With the same ENOB, the energy is reduced to 1.9 µJ when the measurement limits are changed to 100 and 138 k.Peer ReviewedPostprint (published version

Micromachined two dimensional resistor arrays for determination of gas parameters

A resistive sensor array is presented for two dimensional temperature distribution measurements in a micromachined flow channel. This allows simultaneous measurement of flow velocity and fluid parameters, like thermal conductivity, diffusion coefficient and viscosity. More general advantages of measuring temperature distributions are the inherent compensation of heat losses to the support and the insensitivity to variations in the temperature coefficient of resistance

Measuring dynamic signals with direct sensor-to-microcontroller interfaces applied to a magnetoresistive sensor

This paper evaluates the performance of direct interface circuits (DIC), where the sensor is directly connected to a microcontroller, when a resistive sensor subjected to dynamic changes is measured. The theoretical analysis provides guidelines for the selection of the components taking into account both the desired resolution and the bandwidth of the input signal. Such an analysis reveals that there is a trade-off between the sampling frequency and the resolution of the measurement, and this depends on the selected value of the capacitor that forms the RC circuit together with the sensor resistance. This performance is then experimentally proved with a DIC measuring a magnetoresistive sensor exposed to a magnetic field of different frequencies, amplitudes, and waveforms. A sinusoidal magnetic field up to 1 kHz can be monitored with a resolution of eight bits and a sampling frequency of around 10 kSa/s. If a higher resolution is desired, the sampling frequency has to be lower, thus limiting the bandwidth of the dynamic signal under measurement. The DIC is also applied to measure an electrocardiogram-type signal and its QRS complex is well identified, which enables the estimation, for instance, of the heart rate.Postprint (published version

Fabrication of graphene-based resistive sensor for eschericia coli bacteria sensing

The presence of fecal coliform bacteria like Escherichia coli (E. coli) in aquatic environments indicates that the water has been contaminated with the fecal material of human or animals. The risk of health threatening to humans become high when E. coli bacteria are exposed to water, not only causes diarrhea but also lead to death if not treated immediately. Many existing sensors to detect E. coli bacteria are not portable and expensive, while the conventional methods are time consuming and need the sterile procedure. Therefore, it is important to develop a sensor to detect E. coli rapidly, portable and user friendly. In this work, bacteria sensor based on resistivity was developed using graphene nanostructure as a sensing layer, since carbon material like graphene has been known to have a biocompatibility and excellent electrical property. The E. coli bacteria used in this experiment were collected from domestic wastewater and commercial of E. coli strain no. ATCCC 25922. A biochemical test was performed to detect the presence of E. coli in wastewater. The physical characterization of the bacteria was carried out by using FESEM and it was found that the E. coli has size ranging from 1.4-1.6 μm in length. The wettability properties of graphene confirmed that graphene surface is hydrophobic with contact angle of 108.9o which is suitable for bacterial detection. Raman spectroscopy measurements shows that the ratio of G peak and D peak intensity increase due to increase in the number of E. coli. Moreover, the electrical property of graphene shows increasing the number of the bacteria from 4 to 273 colony forming-unit (cfu) result decreasing the resistance from 4.371 to 3.903 ohm gradually. Finally, the sensor was successfully designed using SolidWorks and fabricated by integrating graphene film as a sensing layer with Arduino micro-controller. The validation of the sensor was performed by comparing the data obtained by sensor device and plate culture and has been found to have an error rate of ±12.3%

Microcontroller-Based Seat Occupancy Detection and Classification

This paper presents a microcontroller-based measurement system to detect and confirm the presence of a subject in a chair. The system relies on a single Force Sensing Resistor (FSR), which may be arranged in the seat or backrest of the chair, that undergoes a sudden resistance change when a subject/object is seated/placed over the chair. In order to distinguish between a subject and an inanimate object, the system also monitors small-signal variations of the FSR resistance caused by respiration. These resistance variations are then directly measured by a low-cost general-purpose microcontroller without using either an analogue processing stage or an analogue-to-digital converter, thus resulting in a low-cost, low-power, compact design solution.Peer ReviewedPostprint (published version

Sensor Explosive Concentrations of Hydrogen

The article describes a resistive sensor explosive concentrations of hydrogen with a response time of about 0.1 s is completely selective for hydrogen

Three Realizations and Comparison of Hardware for Piezoresistive Tactile Sensors

Tactile sensors are basically arrays of force sensors that are intended to emulate the skin in applications such as assistive robotics. Local electronics are usually implemented to reduce errors and interference caused by long wires. Realizations based on standard microcontrollers, Programmable Systems on Chip (PSoCs) and Field Programmable Gate Arrays (FPGAs) have been proposed by the authors for the case of piezoresistive tactile sensors. The solution employing FPGAs is especially relevant since their performance is closer to that of Application Specific Integrated Circuits (ASICs) than that of the other devices. This paper presents an implementation of such an idea for a specific sensor. For the purpose of comparison, the circuitry based on the other devices is also made for the same sensor. This paper discusses the implementation issues, provides details regarding the design of the hardware based on the three devices and compares them.This work has been partially funded by the Spanish Government under contracts TEC2006-12376 and TEC2009-14446

Experimental testing of a resistive sensor for monitoring frost formation in refrigeration systems

An experimental study of a resistive sensor is developed. Its performance is evaluated in function of the temperature and relative humidity of air, the temperature of the refrigerant and the relative position of the sensor on the evaporator’s surface. A resistive sensor that include two electrodes measures the electrical resistance of the medium. The experimental study was developed in an experimental facility where different air and refrigerant conditions were set up. The results of the experimental study allowed analyzing the propagation of the frost layer and determining the existence of ice on the evaporator’s surface. The results agreement is satisfactory for water detection and high for the detection of the frost layer. The ice behavioral characteristics plays a key role in frost detection using resistive sensors.info:eu-repo/semantics/publishedVersio

Efficient Sound Card Based Experimention At Different Levels Of Natural Science Education

Sound cards, which count as standard equipment in today's computers, can be turned into measurement tools, making experimentation very efficient and cheap. The chief difficulties to overcome are the lack of proper hardware interfacing and processing software. Sound-card experimentation becomes really viable only if we demonstrate how to connect different sensors to the sound card and provide suitable open-source software to support the experiments. In our talk, we shall present a few applications of sound cards in measurements: photogates, stopwatches and an example of temperature measurement and registration. We also provide the software for these applications.Comment: MPTL-HSCI 2011 Joint conference, 15-17 September 2011, Ljubljana, Sloveni

LIG for Use as a Resistive Sensor

Certain species of sagebrush extant in Idaho emit volatile organic compounds. It is of interest to the scientific community to detect these compounds to glean insight into sagebrush and sage-grouse population decline, or possible intraspecies sagebrush communication. Therefore a sensor is devised to exploit the chemiresistive properties of laser-induced graphene to this end, fabricated by means of irradiating a polyimide with coherent infrared radiation. Properties of the sensory material are discussed, including its resistive response to the compounds of interest, resistive response to temperature, signal interference from physical deformation, and long-term material degradation induced by normal use. Initial results are promising and in line with existing literature. Further research is required to fine-tune the fabrication process