A method for calibration of precision voltage dividers

One phase of electrical measurements which is rapidly becoming more important and requiring higher degrees of accuracy is the measurement of voltage ratio. Conventional 4-arm bridge techniques are often used where two impedances are connected in series, energized from either or both of the voltages whose ratio is being measured, and adjusted so that the voltages across them exactly match the two being compared, both in magnitude and phase angle. The voltage ratio can easily be computed if the characteristics of the impedances are known. Sze has developed a system which uses this technique and will measure voltage ratio with an accuracy of about 50 parts per million (ppm) and phase angle to 0.2 minute at frequencies up to 10,000 cycles per second (cps).1