CALIBRATION PROCEDURE AND UNCERTAINTY ANALYSIS OF AN ELECTRONIC SCALE BASED ON TWO-CURRENT SOURCE SUPPLIED CIRCUIT
Original scientific paper The article presents the prototype version of an original weight scale in which a non-conventional supplying circuit of strain gauge load cells is applied. The paper discusses construction of an electrical circuit, the way of strain gauge transducer connection and the measuring procedure. As far as the authors know, this novel electrical circuit and its application in a weight scale system have never been mentioned in literature. The specifications for directreading weight scales typically include readability, repeatability, linearity and eccentricity. The values of these parameters were estimated and used for calculation of the weight measurement uncertainty in the tested measuring range of the designed device.
Levels and Patterns of Physical Activity and Sedentary Behaviour of Primary School Learners in Lagos State, Nigeria
Background: Physical activity (PA) and sedentary behaviour (SB) assessment in children is critical for the prevention of noncommunicable diseases. African studies examining PA and SB of primary school-age children are few. This study investigated PA, SB levels and their correlates among primary school children in Lagos, Nigeria. Method: In a cross-sectional study of 733 learners, their self-reported PA and SB were assessed using the Children PA Questionnaire (CPAQ) (6–9 years age category) and Youth Activity Profile (YAP) (10–12 years age category) while pedometers were used for objective PA and SB assessment, and socioeconomic status (SES) index were measured using a structured questionnaire. Standardised procedures were used for anthropometric and cardiovascular measures. Results Based on CPAQ, 87.5% and 100% of the learners aged 6–9 years met the recommended PA and SB guidelines, respectively which were lower with pedometers (72.8% and 87.3%). The proportion of boys aged 6–9 years who met the guidelines for PA and SB (using pedometer) was significantly higher than that of the girls(PA: 80.7% vs. 64%, p = 0.018; SB: 94% vs. 80%, p = 0.008). Self-reported PA was positively associated with age (CPAQ: B = 455.39, p < 0.001; YAP: B = 1.638, p = 0.009) and negatively with SES (CPAQ: B = −201.39, p < 0.001; YAP: B = −1.000, p < 0.001). Objective PA was positively associated with waist to hip ratio(WHR) (6–9 years: B = 66090.24, p = 0.032) and negatively with sex (6–9 years: B = −5533.41, p = 0.027) and hip circumference (10–12 years: B = −1269.13, p = 0.017). SB was associated with SES in learners aged 10–12 years (B = −0.282, p = 0.003).Conclusion: High SES is a major predictor of reduced PA among these cohort of learners.
Pressure sensor development using hard anodized aluminum diaphragm and sputtered Pt-W thin film strain sensors
Pressure sensors with a metallic diaphragm and bonded strain gauge are by far the most widely used sensors in pressure measurement. In this work, we describe a method to fabricate a low power, light weight and low cost pressure sensor using aluminum diaphragm. The diaphragm is hard anodized to get insulating base over which Pt-W (Pt: 92%, W: 8%) thin film strain sensors are sputter deposited for sensing the pressure. Hence, this technique eliminates the application of adhesive to bond the strain gauges to the metallic diaphragm. The required level of insulation resistance (in the range of giga-ohms) between the metal diaphragm and the sputtered stain gauge is provided by the hard anodic film. The hard anodic coating is obtained by the wet electrochemical method with pulsed power supply arrangement. The details of diaphragm fabrication, hard anodization of aluminum, testing, calibration of sensor and its applications are discussed and compared with sensors fabricated from different aluminum alloys (AA2024, AA6061 and AA7075).