Sensor Attachment Research Articles

Cryogenic thermometry for refrigerant distribution system of JT-60SA

JT-60SA is a fully superconducting fusion experimental device involving Japan and Europe. The cryogenic system supplies supercritical or gaseous helium to superconducting coils through valve boxes or coil terminal boxes and in-cryostat pipes. There are 86 temperature measurement points at 4 K along the distribution line. Resistance temperature sensors will be installed on cooling pipes in vacuum. In this work, two sensor attachment methods, two types of sensor, two thermal anchoring methods, and two sensor fixation materials have been experimentally evaluated in terms of accuracy and mass productivity. Finally, the verification test of thermometry has been conducted using the sample pipe fabricated in the same way to the production version, which has been decided by the comparison experiments. The TVO sensor is attached by the saddle method with Apiezon N grease and the measurement wires made of phosphor bronze are wound on the pipe with Stycast 2850FT as the thermal anchoring. A Cernox sensor is directly immersed in liquid helium as a reference thermometer during the experiment. The measured temperature difference between the attached one and reference one has been within ±15 mK in the range of 3.40-4.73 K. It has satisfies the accuracy requirement of 0.1 K.

Remote monitoring of breathing dynamics using infrared thermography.

An atypical or irregular respiratory frequency is considered to be one of the earliest markers of physiological distress. In addition, monitoring of this vital parameter plays a major role in diagnosis of respiratory disorders, as well as in early detection of sudden infant death syndrome. Nevertheless, the current measurement modalities require attachment of sensors to the patient's body, leading to discomfort and stress. The current paper presents a new robust algorithm to remotely monitor breathing rate (BR) by using thermal imaging. This approach permits to detect and to track the region of interest (nose) as well as to estimate BR. In order to study the performance of the algorithm, and its robustness against motion and breathing disorders, three different thermal recordings of 11 healthy volunteers were acquired (sequence 1: normal breathing; sequence 2: normal breathing plus arbitrary head movements; and sequence 3: sequence of specific breathing patterns). Thoracic effort (piezoplethysmography) served as "gold standard" for validation of our results. An excellent agreement between estimated BR and ground truth was achieved. Whereas the mean correlation for sequence 1-3 were 0.968, 0.940 and 0.974, the mean absolute BR errors reached 0.33, 0.55 and 0.96 bpm (breaths per minute), respectively. In brief, this work demonstrates that infrared thermography is a promising, clinically relevant alternative for the currently available measuring modalities due to its performance and diverse remarkable advantages.

Behavior of Humidity Sensors Attached With Anisotropic Electrically Conductive Adhesives in Corrosive Environment

Sensors are used increasingly in different applications. In some of these applications, they need to be able to tolerate harsh environments and also operate for long periods of time. One of the most challenging environments is corrosive media which may be present in many applications. In this paper, the reliability of humidity sensors attached to an FR-4 substrate was studied using a salt spray test to determine their tolerance for corrosion. Because of their structure, the attachment methods for the sensor components were restricted. Consequently, the sensor components were attached using flip chip technology with two different anisotropic conductive adhesives (ACAs). Afterward, the reliability of the sensor components was investigated using the salt spray test. During testing resistance of the ACA interconnection was measured in real time. To extract the failure mechanism, an extensive failure analysis was performed with scanning electron microscopy. The main failure mechanism was found to be corrosion of a polymer film in the sensor component. The results showed that ACA is promising material for sensor attachments, as most of the sensor components were able to withstand a considerable period of time under the salt spray test without failures.

Development of an objective mental workload assessment tool based on Rasmussen's skill–rule–knowledge framework

It is important to monitor operators’ mental workload during the operation phase. Physiological measurement approaches could record the operator's mental data continuously, and might be less interruptive on the work activities. However, these methods often require the attachment of physical sensors, which are not unobtrusive in the physical sense. Furthermore, the individual difference makes calibrating to each individual tedious and requires trained persons to use. Often high noise-to-signal ratio data are hard to analyze. Due to these factors, physiological workload measurements are hardly widely applied in practical fields. In this study, an objective, non-intrusive and performance-based mental workload predictive model was proposed with high validity (R2 = 0.51), which can be applied during the operation phrase. This model, developed based on the Rasmussen's skill–rule–knowledge framework, is comprised of two novel cognitive indices, the attention required index and uncertainty index. It can be used as the basis for establishing an early online warning system automatically. Furthermore, this model also predicts the types of error-prone tasks. This kind of information is expected to provide managers and supervisors with opportunities to intervene and improve tasks before error occurred. Finally, the predictive model proposed in this paper requires more practical application in fields to be completed.

Lightweight physiologic sensor performance during pre-hospital care delivered by ambulance clinicians.

The aim of this study was to explore the impact of motion generated by ambulance patient management on the performance of two lightweight physiologic sensors. Two physiologic sensors were applied to pre-hospital patients. The first was the Contec Medical Systems CMS50FW finger pulse oximeter, monitoring heart rate (HR) and blood oxygen saturation (SpO2). The second was the RESpeck respiratory rate (RR) sensor, which was wireless-enabled with a Bluetooth® Low Energy protocol. Sensor data were recorded from 16 pre-hospital patients, who were monitored for 21.2 ± 9.8 min, on average. Some form of error was identified on almost every HR and SpO2 trace. However, the mean proportion of each trace exhibiting error was <10 % (range <1–50 % for individual patients). There appeared to be no overt impact of the gross motion associated with road ambulance transit on the incidence of HR or SpO2 error. The RESpeck RR sensor delivered an average of 4.2 (±2.2) validated breaths per minute, but did not produce any validated breaths during the gross motion of ambulance transit as its pre-defined motion threshold was exceeded. However, this was many more data points than could be achieved using traditional manual assessment of RR. Error was identified on a majority of pre-hospital physiologic signals, which emphasised the need to ensure consistent sensor attachment in this unstable and unpredictable environment, and in developing intelligent methods of screening out such error.

Inter- and intra-tester reliability when measuring seated spinal postures with inertial sensors

Prolonged awkward sitting postures may be associated with neck or back pain, but it is often unclear which specific postures cause most problems and which mechanisms that may underlie the pain. In order to increase the knowledge in this field, it seems crucial first of all to be able to analyse, in depth, different seated spinal postures. A problem is however the lack of reliable and direct measurement methods of the posture, especially for sitting. Recently developed systems with inertial sensor attached along the spine have potential for this purpose. The aim of the present study was therefore to test the reliability of using such a system to assess various seated postures.Inter- and intra-tester as well as intra-subject relative reliability was estimated with intra-class correlation coefficient (ICC). Absolute reliability was estimated with standard error of measurement (SEM) and smallest detectable change (SDC). Ten + ten healthy subjects and four testers participated. Three standardised unsupported seated postures (lumbar lordosis, lumbar kyphosis and neutral posture) and two standing postures (neutral and lumbar kyphosis) were evaluated using five sensors attached to the head, the thorax (high and low), the lumbar spine and the pelvis. The ICC for intra-tester reliability ranged from 0.37 to 0.90, SEM 2.5–12.0°, and SDC 7.1–33.3° where the largest measurement error was from the head. Intra-tester reliability was higher than inter-tester reliability but not as good as intra-subject reliability. The intra-tester absolute reliability was nevertheless not considered sufficient to distinguish smaller differences. The low reliability may depend on inertial sensor size and attachment but also on the tester's accuracy. This study shows that assessing unsupported seated spinal postures with inertial sensors could be performed with higher reliability if done by the same, rather than different, testers. Relevance to industryProlonged awkward seated postures at work may be associated with back and neck pain and should therefore be analysed. Inertial sensor units is a promising tool to measure spinal posture. Smaller sensors attached by one skilled tester directly onto the body will most likely improve assessment in the future.

High temperature reliability of electrically conductive adhesive attached temperature sensors on flexible polyimide substrates

The attachment and packaging of temperature sensors may be challenging due to their structure and materials. Sensing requires a structure which is open to the environment and the materials often differ from those used in silicon-based electronics. Thus, traditional attachment techniques and materials such as soldering may be inappropriate. Polymer-based electrically conductive adhesives (ECA) are an alternative. The operating environment of a sensor may, however, be very demanding. Very little research data is available on the use of ECAs in challenging conditions, thus restricting their use in many applications. This study tested the behaviour of temperature sensors attached with ECAs onto flexible polyimide (PI) substrates in thermal storage at 200°C. More than 1000h of testing without failures were conducted on the ECA sensor structures. Good high temperature reliability therefore seems to be possible with ECAs. However, the PI substrate was observed to be critical to reliability. An adhesive layer used in the PI substrate reacted at the test temperature and severe oxidation of the copper pads and reaction between the materials consequently destroyed the interconnection and caused failures.

Preliminary study for the assessment of physical activity using a triaxial accelerometer with a gyro sensor on the upper limbs of subjects with paraplegia driving a wheelchair on a treadmill.

This study aimed to examine whether, on the basis of the relationship between sensors attached on the upper limbs and energy expenditure (EE) at the time of wheelchair propulsion, there are differences in the measurement of EE depending on the sensor attachment site and whether addition of the angular velocity information to the acceleration value is advantageous. We also aimed to clarify the variables used to estimate EE as well as the estimated error. Laboratory of the National Hospital Organization Murayama Medical Center, Japan. Six male subjects with spinal cord injuries participated in the study. Each wore sensors at the wrist and the middle upper arm on both sides while driving a wheelchair on a treadmill at three levels: very, very light; very light; and fairly light. Triaxial acceleration, triaxial angular velocity and EE were measured during driving. We analyzed the correlation between EE and acceleration, angular velocity and synthesized values of acceleration and angular velocity at each location using regression, multiple regression and Bland-Altman analyses. The determination coefficients between EE and the acceleration, angular velocity and synthesized values of acceleration and angular velocity varied from 0.68 to 0.87 at each location. The mean difference between the measured and estimated EE varied from 0.0028 (s.d., 0.0027) kcal min(-1) kg(-1) on the right upper arm. These findings suggest that combining the synthesized values of angular velocity and acceleration of the motion sensors on the upper limbs might reflect EE during a wheelchair driving activity on a treadmill.

Automatic identification and removal of ocular artifacts in EEG--improved adaptive predictor filtering for portable applications.

Electroencephalogram (EEG) signals have a long history of use as a noninvasive approach to measure brain function. An essential component in EEG-based applications is the removal of Ocular Artifacts (OA) from the EEG signals. In this paper we propose a hybrid de-noising method combining Discrete Wavelet Transformation (DWT) and an Adaptive Predictor Filter (APF). A particularly novel feature of the proposed method is the use of the APF based on an adaptive autoregressive model for prediction of the waveform of signals in the ocular artifact zones. In our test, based on simulated data, the accuracy of noise removal in the proposed model was significantly increased when compared to existing methods including: Wavelet Packet Transform (WPT) and Independent Component Analysis (ICA), Discrete Wavelet Transform (DWT) and Adaptive Noise Cancellation (ANC). The results demonstrate that the proposed method achieved a lower mean square error and higher correlation between the original and corrected EEG. The proposed method has also been evaluated using data from calibration trials for the Online Predictive Tools for Intervention in Mental Illness (OPTIMI) project. The results of this evaluation indicate an improvement in performance in terms of the recovery of true EEG signals with EEG tracking and computational speed in the analysis. The proposed method is well suited to applications in portable environments where the constraints with respect to acceptable wearable sensor attachments usually dictate single channel devices.

On the importance of telemetric temperature sensor location during intraperitoneal implantation in rats

This study aims to assess the thermal homogeneity of the intraperitoneal (IP) cavity and the relevance of using a fixed telemetric temperature sensor at a given location in studying rodents. Ten rats were intraperitoneally implanted with three Jonah® capsules each; after assessing the accuracy and reliability of the sensors. Two capsules were attached, one to the right iliac fossa (RIF) and the other to the left hypochondrium (LH), and another was placed between the intestines but not attached (Free). In the ex vivo condition, the differences between sensors and reference values remained in the range of ±0.1. In the invivo condition, each sensor enabled the observation of temperature patterns. However, sensor location affected mean and median temperature values while the rats were moving freely. Indeed, temperature data collected in the LH were 0.1 significantly higher than those collected in the RIF and temperature data collected in the LH were 0.11 significantly higher than those collected with the Free capsules. In invivo conditions, intra-sensor variability of temperature data was not affected by sensor location. Taking into account sensor accuracy, similar intra-sensor variability, and mean differences observed between the three locations, the impact of sensor location within the IP cavity could be considered negligible. In invivo conditions, temperature differences between locations regularly exceeded ±0.2 and reached up to 2.5. These extreme values could be explained by behavioral factors such as food or water intake. Finally, considering the good thermal homogeneity of the IP cavity and possible adverse consequences of sensor attachment, it seems better to let sensors range free within the cavity.

Non-invasive damage detection in beams using marker extraction and wavelets

For structural health monitoring applications there is a need for simple and contact-less methods of Non-Destructive Evaluation (NDE). A number of damage detection techniques have been developed, such as frequency shift, generalised fractal dimension and wavelet transforms with the aim to identify, locate and determine the severity of damage in a material or structure. These techniques are often tailored for factors such as (i) type of material, (ii) damage pattern (crack, delamination), and (iii) the nature of any input signals (space and time). This paper describes and evaluates a wavelet-based damage detection framework that locates damage on cantilevered beams via NDE using computer vision technologies. The novelty of the approach is the use of computer vision algorithms for the contact-less acquisition of modal shapes. Using the proposed method, the modal shapes of cantilever beams are reconstructed by extracting markers using sub-pixel Hough Transforms from images captured using conventional slow motion cameras. The extracted modal shapes are then used as an input for wavelet transform damage detection, exploiting both discrete and continuous variants. The experimental results are verified and compared against finite element analysis. The methodology enables a non-invasive damage detection system that avoids the need for expensive equipment or the attachment of sensors to the structure. Two types of damage are investigated in our experiments: (i) defects induced by removing material to reduce the stiffness of a steel beam and (ii) delaminations in a (0/90/0/90/0)s composite laminate. Results show successful detection of notch depths of 5%, 28% and 50% for the steel beam and of 30mm delaminations in central and outer layers for the composite laminate.

Orientation-Compensative Signal Registration for Owner Authentication Using an Accelerometer

SUMMARY Gait-based owner authentication using accelerometers has recently been extensively studied owing to the development of wearable electronic devices. An actual gait signal is always subject to change due to many factors including variation of sensor attachment. In this research, we tackle to the practical sensor-orientation inconsistency, for which signal sequences are captured at different sensor orientations. We present an iterative signal matching algorithm based on phase-registration technique to simultaneously estimate relative sensor-orientation and register the 3D acceleration signals. The iterative framework is initialized by using 1D orientation-invariant resultant signals which are computed from 3D signals. As a result, the matching algorithm is robust to any initial sensororientation. This matching algorithm is used to match a probe and a gallery signals in the proposed owner authentication method. Experiments using actual gait signals under various conditions such as different days, sensors, weights being carried, and sensor orientations show that our authentication

Monitoring and Analysis of Respiratory Patterns Using Microwave Doppler Radar.

Noncontact detection characteristic of Doppler radar provides an unobtrusive means of respiration detection and monitoring. This avoids additional preparations, such as physical sensor attachment or special clothing, which can be useful for certain healthcare applications. Furthermore, robustness of Doppler radar against environmental factors, such as light, ambient temperature, interference from other signals occupying the same bandwidth, fading effects, reduce environmental constraints and strengthens the possibility of employing Doppler radar in long-term respiration detection, and monitoring applications such as sleep studies. This paper presents an evaluation in the of use of microwave Doppler radar for capturing different dynamics of breathing patterns in addition to the respiration rate. Although finding the respiration rate is essential, identifying abnormal breathing patterns in real-time could be used to gain further insights into respiratory disorders and refine diagnostic procedures. Several known breathing disorders were professionally role played and captured in a real-time laboratory environment using a noncontact Doppler radar to evaluate the feasibility of this noncontact form of measurement in capturing breathing patterns under different conditions associated with certain breathing disorders. In addition to that, inhalation and exhalation flow patterns under different breathing scenarios were investigated to further support the feasibility of Doppler radar to accurately estimate the tidal volume. The results obtained for both experiments were compared with the gold standard measurement schemes, such as respiration belt and spirometry readings, yielding significant correlations with the Doppler radar-based information. In summary, Doppler radar is highlighted as an alternative approach not only for determining respiration rates, but also for identifying breathing patterns and tidal volumes as a preferred nonwearable alternative to the conventional contact sensing methods.

Non-invasive Muscle Temperature Control during Cooling

The aim of this work was to investigate the possibilities of using the non-invasive method to control the temperature of deep layers in limb tissues during cooling, using thermistors as temperature sensors. The invasive temperature control of the deep tissue layers is not always acceptable to the test subject. The temperature distribution was simulated using computer software, when the limb was cooled in the +15 °C temperature water bath and frozen by adding the ice pack. The temperature was measured experimentally by using thermistor as a temperature sensor. The uncertainty of calibrated temperature transducer was ±0.05 °C. The 3 cm thickness layer of thermal insulation separated the temperature sensor from the cooling agent. After 30 min of cooling the tissue surface temperature at the sensor attachment point was 31.5±0.65 °C. During modeling it was determined, that in case when temperature underneath the sensor was 31.5 °C, then the tissue temperature in 30 mm depth should be 31.9 °C, what corresponds to the temperature values determined by other researchers using invasive measurements under analogous conditions. On the basis of the study results the structure of a hand-held device for control of temperature in deeper muscle layers via measurement of the skin surface temperature was offered. DOI: http://dx.doi.org/10.5755/j01.eee.19.9.5647

Removal of Ocular Artifacts in EEG—An Improved Approach Combining DWT and ANC for Portable Applications

A new model to remove ocular artifacts (OA) from electroencephalograms (EEGs) is presented. The model is based on discrete wavelet transformation (DWT) and adaptive noise cancellation (ANC). Using simulated and measured data, the accuracy of the model is compared with the accuracy of other existing methods based on stationary wavelet transforms and our previous work based on wavelet packet transform and independent component analysis. A particularly novel feature of the new model is the use of DWTs to construct an OA reference signal, using the three lowest frequency wavelet coefficients of the EEGs. The results show that the new model demonstrates an improved performance with respect to the recovery of true EEG signals and also has a better tracking performance. Because the new model requires only single channel sources, it is well suited for use in portable environments where constraints with respect to acceptable wearable sensor attachments usually dictate single channel devices. The model is also applied and evaluated against data recorded within the EUFP 7 Project--Online Predictive Tools for Intervention in Mental Illness (OPTIMI). The results show that the proposed model is effective in removing OAs and meets the requirements of portable systems used for patient monitoring as typified by the OPTIMI project.

Investigation on the Molecular Shear-Induced Organization in a Molecularly Thin Film of N-hexadecane

The frictional properties of a thin hexadecane film confined between two atomically smooth surfaces of mica were studied using the surface forces apparatus equipped with a 3D actuator–sensor attachment specially designed to investigate static and dynamic forces in three orthogonal directions simultaneously. The use of this attachment allows the relative alignment of the reciprocal sliding motion to be changed by an angle of 90° while maintaining the film under the same confinement conditions. The effects of the commensurability of the confining mica surfaces as well as the relative sliding direction on the frictional behavior of the hexadecane film were determined for different temperatures (18–29 °C) and sliding velocities (4 nm/s to 4 μm/s). The confined hexadecane film exhibited smooth sliding friction whose amplitude increased with the commensuration of the surfaces. A progressive evolution in the kinetic friction force toward a steady-state value was observed over reciprocal sliding motion for given experimental conditions of applied load, sliding velocity and environmental temperature. This friction evolution shows to be dependent on the sliding history of the film and could result from a partial molecular ordering, occurring during shear.

Formant Frequency as a Measure of Physical Fatigue

Objective: The current study investigated a non-obtrusive measure for detecting physical fatigue based on the analysis of formant frequencies of human voice. Background: Fatigue has been considered as a main cause in industrial and traffic accidents. Therefore, it is critical to detect worker"s fatigue for accident prevention. Method: After running exercises on a treadmill, participants were instructed to read a sentence and their voices were recorded under four different physical fatigue levels. Korean vowels of "아", "어", "오", "우", and "이" from the voice recorded were then used to collect formant 1 frequencies. Results: Results of separate ANOVAs showed a significant main effect of physical fatigue on formant 1 frequency of "아", "어", and "이". Furthermore, post-hoc comparisons revealed that formant 1 frequency of "아" was most sensitive to physical fatigue level employed in this experiment. Conclusion: Formant 1 frequencies of some vowels significantly decrease as the physical fatigue level increases. Application: Potential application of this study includes the development of a measure of physical fatigue state that is free from sensor attachment and requires little preparation.

An unusual case of facial burn in which a flammable, alcohol-free liquid barrier film caught fire probably from static electricity when a bispectral index sensor was applied to the patient

To the Editor: Bispectral index (BIS , Aspect Medical Systems Inc., Natick, MA, USA) monitoring is useful for measuring the depth of anesthesia, but the sensor can cause skin lesions [1, 2]. In our hospital, an alcohol-free liquid barrier film (Cavilon) is used for skin protection. We recently encountered a case in which this liniment caught fire probably due to static electricity upon BIS sensor attachment. A 76-year-old male patient (height 164 cm, weight 54 kg) was diagnosed with rectal cancer and was scheduled for rectal resection (Hartmann’s procedure). He had complications of rheumatoid arthritis and interstitial pneumonia. Preoperative tests revealed slight anemia (hemoglobin 11.0 g/dl), restrictive ventilatory impairment (vital capacity was 55.3 %), and ground-glass opacity on a chest X-ray image. Other tests showed no abnormalities. After arrival at the operating room, administration of 6 l/min oxygen was started via a face mask, and the patient’s forehead was wiped with an isopropanol pad. After alcohol evaporation, his forehead was smeared with a Cavilon stick. When we were about to attach a BIS sensor to him, a fire suddenly flared up on his forehead. The fire burned his eyebrows and paper cap, and went out quickly. The skin of the forehead showed an erythematous change (Fig. 1). We applied a steroidal ointment to the erythematous lesion and started cooling. We explained the situation to the patient and his family and continued the anesthesia and operation without BIS monitoring. Anesthesia was induced and maintained with propofol (target-controlled infusion 2.0–2.5 mcg/ml) and remifentanil (continuous infusion 0.6–1.0 mcg/kg/min) throughout the operation. The operation was completed uneventfully, and the patient awoke from the anesthesia without delay. Although his burn site developed blisters, the lesion was cured by conservative treatment about 30 days after surgery. Fires in operating rooms are rare but preventable dangers. It is estimated that about 600 surgical fires occur in the USA annually. Fire consists of three components: an oxidizer, an ignition source, and a fuel [3]. It is reported that a common oxidizer contributing to many surgical fires during head and neck surgery is a high concentration of oxygen via a face mask [4], as in this case. Most ignition sources are electrosurgical or laser devices, defibrillators, and light sources. In this case, no ignition source was close to the patient, and the BIS sensor was not connected to the power. Static electricity might have been generated between the patient and the BIS sensor. Fuels are flammable prepping agents, disinfectants, and medical materials such as drapes and tubes. Cavilon is a skin barrier film used for skin protection. As it contains some flammable contents with a flash point of -6.7 C, and as the lower flammability concentration is 0.7 %, the material safety data sheet states the precaution that all ignition sources such as heat, flames, or sparks should be removed. In conclusion, to prevent fires in operating rooms, we should always consider the flammability of agents used on the face, head, and neck when the patient is receiving oxygen via a face mask. M. M. Wakimoto K. S. Suzuki (&) Department of Anesthesiology, School of Medicine, Iwate Medical University, Uchimaru 19-1, Morioka, Iwate 020-8505, Japan e-mail: kenjis@iwate-med.ac.jp

Automatic recognition and classification of cattle chewing activity by an acoustic monitoring method with a single-axis acceleration sensor

Monitoring the eating habits and rumination of cattle is effective for evaluating forage values and making animal management decisions for stalls and grazing pastures. Acoustic monitoring is a feasible method to monitor these activities, but it requires automatic distinction and quantification of activities to gain broader application. This automatic distinction and quantification may be possible using a pattern matching method, which distinguishes jaw movements by extracting characteristic patterns from eating and ruminating, and then matches similar characteristic patterns in unanalyzed activities. The objectives of this study were to define an acoustic monitoring system with a single-axis acceleration sensor, to determine an effective sensor attachment site (i.e., the horn, forehead, or nasal bridge), and to assess the automatic classification of ingestive and ruminative chewing behaviors using a pattern matching method. Four beef cows fed Italian ryegrass silage were each recorded eating and ruminating for more than 60 and 20min, respectively. The oscillatory waveforms generated while eating and ruminating were clearly recorded by the single-axis acceleration sensor, regardless of sensor attachment site. The pattern matching method correctly distinguished ingestive chewing with an accuracy of over 0.9, regardless of the sensor site (estimated number of chews by automatic detection/true number of chews by manual detection). Placement of the sensor on the horn of the animal resulted in the most matched measurement (0.99). In contrast, the method overestimated ruminating chewing time (approximately 1.50) because noises that occurred during idling were misclassified as ruminating chewing. The provision of an additional chewing criterion for automatic detection, i.e., chewing is performed consecutively (context-based cues), improved the classification accuracy of ruminating to a range of 1.02–1.08. In conclusion, automatic detection using a pattern matching method successfully classified ingestive chewing and ruminating chewing in cattle, and a single-axis acceleration sensor was useful for acoustic monitoring at all sensor attachment sites.

Effects of accelerometer coupling on step counting accuracy in healthy older adults

Motion artefact and signal noise represent challenges when sensor technology is incorporated within clothing. The aim of this study is to assess the effect that device/body coupling has on an accelerometer’s ability to function accurately as a step counter. Data were recorded from 12 subjects (male n = 6) as they walked on a motorised treadmill at speeds of 0.89 m/s and 1.34 m/s. Each subject wore three accelerometers attached directly to the skin. These were located at the sternum, lower back and waist. Three further accelerometers were placed in a harness structure that was worn by the subject. These were located in the same positions as the skin attached accelerometers (sternum, lower back and waist). Increased noise was evident in the signals obtained from accelerometers positioned within the harness. This was evident in an increased peak amplitude and resonance at roughly the same time each heel strike occurred. The signal to noise ratio (SNR) at the waist was significantly lower than that at the sternum (p < 0.001) and lower back (p < 0.001). The method of sensor attachment (skin versus harness) had no significant effect on the accuracy of step count obtained from devices at the sternum (p = 0.962), waist (p = 0.894) or lower back (p = 0.729). This study has shown that accelerometer coupling has no significant effect on step count accuracy. Nevertheless, walking represents only a small part of normal daily physical activity. Further investigation is required to assess the effect of accelerometer /body coupling under free living conditions.