High value resistance comparison using modified Wheatstone bridge based on current detection

• Modified Wheatstone bridge was developed for high value resistance comparison.
• Advantage of current detection method in bridge balance was evaluated.
• A simple “4-step” bridge balancing procedure is suggested.
• Virtual grounding of measured resistors reduces parasitic capacitive currents.
• Ratio of compared high resistance standards can be measured at ppm level.

In this paper is presented the method for comparison of high value resistance standards by using the modified Wheatstone bridge and picoammeter as current detector. The advantage of current detection method over voltage detection method in bridge balancing using available laboratory equipment was evaluated. A four-step procedure for accurate and fast balancing of the bridge is explained. Experimental results confirm that resistance ratios in gigaohm range can be determined with relative uncertainties of only a few parts per million (ppm). By measuring the ratio on the level of 10:1, this method is introduced in Primary Electromagnetic Laboratory (PEL) for maintaining traceability chain of reference standards ranging from 10 MΩ to 100 GΩ.