Novel Resistance Measurement Method: Analysis of Accuracy and Thermal Dependence with Applications in Fiber Materials

Abstract

Material resistance is important since different physicochemical properties can be extracted from it. This work describes a novel resistance measurement method valid for a wide range of resistance values up to 100 GΩ at a low powered, small sized, digitally controlled and wireless communicated device. The analog and digital circuits of the design are described, analysing the main error sources affecting the accuracy. Accuracy and extended uncertainty are obtained for a pattern decade box, showing a maximum of 1% accuracy for temperatures below 30 ∘C in the range from 1 MΩ to 100 GΩ. Thermal analysis showed stability up to 50 ∘C for values below 10 GΩ and systematic deviations for higher values. Power supply Vi applied to the measurement probes is also analysed, showing no differences in case of the pattern decade box, except for resistance values above 10 GΩ and temperatures above 35 ∘C. To evaluate the circuit behaviour under fiber materials, an 11-day drying process in timber from four species (Oregon pine-Pseudotsuga menziesii, cedar-Cedrus atlantica, ash-Fraxinus excelsior, chestnut-Castanea sativa) was monitored. Results show that the circuit, as expected, provides different resistance values (they need individual conversion curves) for different species and the same ambient conditions. Additionally, it was found that, contrary to the decade box analysis, Vi affects the resistance value due to material properties. In summary, the proposed circuit is able to accurately measure material resistance that can be further related to material properties.

Sensor Node Network for Remote Moisture Measurement in Timber Based on Bluetooth Low Energy and Web-Based Monitoring System

“…The moisture sensor device described in [ 15 ] was formed of two main parts: analog part containing the amplification and filtering section, responsible for resistance measurement; and a digital part that reads the sensed values from the analog part and transmits them via Wi-Fi. The analog part and the digital part were designed as two separated boards to minimize interference, and to make the design more flexible.…”

“…The authors have previously developed [ 15 ] a device with a novel and accurate resistance measurement method: the resistance value of any material or substance can be obtained and then converted into a physicochemical magnitude “e.g., moisture content in percentage”. In this paper, this measurement device was adapted to build an IoT network system for remote monitoring of the moisture content of wood through a web application running on computers and smartphones.…”

Novel Wood Resistance Measurement Method Reducing the Initial Transient Instabilities Arising in DC Methods Due to Polarization Effects

“…Obviously, these methods are not applicable in case of wood already fixed in a building, timber or furniture. Indirect methods are based on the measurement of a physical property of wood heavily dependent on its moisture content [3], such as the electrical resistance for the so-called resistive methods [8][9][10][11], dielectric constant for the capacitive [4,12] or microwave methods [13], sorption capacity methods [14] and others [3].…”

“…Concerning resistive measurement methods, both direct current (DC) [8][9][10][11] or alternating current (AC) [21,22] can be applied to the electrodes in order to determine its equivalent resistance R. In the DC resistance measurement method, a polarization effect exists, which results in a transient response in the measured resistance [6,7,18]. To minimize this polarization effect, References [21,22] propose to alternate the polarity of the voltage applied to the electrodes, that is, the application of an alternating current (AC).…”

Development of instrumentation setup for discrimination of analytes using principal component analysis

“…A sensor array consists of a combination of sensors, which are based on the change in electrical property with the change of analyte. The electronic circuit measures the conductivity of the sensor [20][21][22][23]. Data acquisition software collects the sensor data and saves in a file for post analysis [24][25][26][27].…”