High-resistance measuring standards of electrical resistance

Measuring standards of electrical resistance are developed to cover the .1 to 10 to the 7th power ohm range, with a standard deviation of from five times ten to the minus 7th to .0001 at frequencies from 20 Hz to 50 kHz. A coil of microwave wound on a hollow glass bobbin is slipped into a glass cylinder, the ends of which are then hermetically sealed, whereupon the entire unit is placed in a rectangular metal canister. The canister is grounded on the outside and lined with a resistive microwire-mesh shield inside. These resistance standards are calibrated and tested for certification against etalons with the aid of class-1 comparators, a digital voltmeter and a semiautomatic bridge.