High-Precision Digital Volt Ratiometer by a Method of Measuring Difference of Magnetic Field among Three Windings

The purpose of this work is to establish a highly accurate automatic ratio measuring instrument for dc voltage and resistance. In voltage and resistance ratio measurements, accuracy of 0.1 ppm has now become necessary due to recent developments in quantum metrology. To obtain the accuracy, we have just developed a technique to automatically compensate the measuring error caused by the deviation of electrical components, such as resistances used in the instrument. The instrument described incorporates this technique. With internal reference voltage and resistance, it can be a precision voltohmmeter and also, it can be standardized to an external standard with an accuracy of 0.1 ppm.