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This paper concerns the development and design of filtering and linearization stage of potentiometric transducer to measure human stress level based on salivary amylase activity. The design of this new way approached is implemented using Cadence OrCAD Capture CIS 15.7 software and hardware construction and troubleshooting. From the previous research, it has been found that for a sensor input range of 1.1 to 1.3 kilo ohms, an output range of -100 to +100 millivolts is obtained. The design for filtering stage used the first order passive low pass filter to accommodate the stress signal frequency for 0.4Hz. Besides the design also focus to boost up the low voltage input of 108.6mV - (-100mV) to 0V-5V output voltage. Its involved low pass filter, voltage follower and linearization stages. The result indicates discrepancy within 4.5% and 3.7% were found between the simulation and experimental results for voltage follower after filtering and linearization circuit respectively, on the average. This development allowed stress measurement with relatively high precision and accuracy.
Date of Conference: 7-10 May 2010