This thesis presented the design and construction of an adaptive active band-pass filter by using a tachometer circuit. The main part was the multi voltage-mode filter circuit based on an operational transconductance amplifier which could automatically adjust the center frequency to adapt to the input signal frequency by the tachometer circuit. The frequency error value in the center frequency was set to be ≤ 3% of the input signal. Furthermore the proposed filter could support the input signal in the frequency range of 10 Hz - 10 kHz. From the simulation and experimental results of the proposed prototype filter it could respond to the frequency according to the theory of the band-pass filter and the error in choosing the center frequency which was 1.45 % and 2.6 % respectively (below the set error value of 3 %). Therefore the proposed filter could be used for real application. The working principles of the proposed prototype filter could also be applied to the noise attenuation circuit of an electrocardiogram machine. Moreover this research could be used as a guideline study for those who want to develop other types of adaptive active filters for higher efficiency.

In general the measured resistance with a digital multimeter. Users tend to be measured and then displayed on the screen to the user regardless of the value that is accurate or not. The value displayed on screen digital multimeter may be incorrect. As a result from wires access point measurement and other factor that affect to the value of measurement. Thus the study of factors that affect the measurement to get the accurate and more precise and also can be used in the operations. According to international standard quality system requirements for ISO are clearly on the meter or the measuring device must be calibrated and in the certificate specifies the gain calibration and the uncertainty of measurement. Therefore it is necessary to evaluate the uncertainty of measurement to comply with the standard splash. This thesis presents a study of the effect to the measurement resistance in 0.01 ohm to 100 mega-ohm by direct measurement for 2wire & 4wire Loading effect Using different kinds of conductors Thermal EMF and the stability of the resistor. Include the statistical analysis was used to estimate the uncertainty. From this study can be applied to measure the resistance in a variety of accurately and precisely.