engleski

Calibration of 100 Mohm Hamon resistor using current-sensing Wheatstone bridge

Primary electromagnetic laboratory in Zagreb maintains standards of four major electromagnetic units: volt, farad, ohm and second. Reference standards are periodically calibrated in PTB (Germany) and several methods has been realized for internal laboratory traceability check. RC-comparison method uses Hamon divider constructed of 100 equally balanced 1-megaohm resistors that connected in parallel or serially exhibit Hamon ratio of 100 Mohm : 10 kohm with relative uncertainty of 10-8. Hamon resistance of 100 Mohm is directly compared with impedance of 100 pF capacitance reference at frequency of 15, 873 Hz. Measurement of low-frequency voltage ratio is based on two digital voltmeters HP 3458A with improved algorithm for data processing. Accuracy of reference standards comparison 10 kohm - 100 pF depends on consistency of Hamon divider that can be disturbed by aging of used metal-film components. In this paper a recently realized method for accurate measurement of 100 Mohm Hamon resistor by means of comparison with calibrated and stable 10 Mohm resistance standard at higher voltage levels has been presented.

resistor calibration ; Hamon divider ; current-sensing detector

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