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This work deals with the designing of an oscillator based bridge set-up that can be used for in-circuit resistance measurement for a wide range of values. The circuit utilizes op-amp based active bridge in integration with relaxation oscillator to convert the resistance change into time period or duty cycle. The addition of an oscillator makes the bridge self-sustaining in nature. A novel, low cost,...
A setup has been developed for the accurate calibration of DC current ratios for DC currents up to 600 A. The setup is based on a DC current comparator and suitable for the calibration of DC current ratio measurement devices up to 100 A primary current. For higher primary currents, multiple turns of the primary conductor are made through the device under test. It has been verified that for well-designed...
An overview is presented on precision high-ohmic resistance measurements for values of 100 MΩ and above. The two main measurement techniques in this resistance range are discussed, the current integration technique and the adapted Wheatstone bridge. The quality of high-ohmic resistance standards, especially their time constants, temperature and voltage dependence, often is limiting the final uncertainty...
The load effect of the resistor should be paid great attention for the precise measurement. Here a high accurate resistance voltage divider (RVD) used to precisely measure the load effect of the resistor is provided. A self-calibrated standard resistor at 100Ω with zero load effect is employed as one arm of the bridge, and several stable resistors with the same temperature coefficient and structure...
This paper describes the thermal characterization of a coaxial calculable resistor, part of traceability chain of the capacitance unit to the quantum Hall effect, in construction at Inmetro. The realization of the capacitance unit (farad) is related to the QHE by a calculable coaxial resistor, and three low-uncertainty coaxial bridges: the two-terminal and the four-terminal bridges, already in operation...
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