Measuring system for detecting polarity of direct current - senses voltages across windings for comparison with excitation voltage

摘要

The direction of flow of direct current in a conductor is detected by comparison with an excitation voltage and overcomes problems experienced when saturable transformers are used. Direct current (IDC) flowing in a conductor is detected by a circuit comprising a winding (10) and an excitation voltage supply (14). The winding produces a voltage output dependent on the direct current and a comparison circuit (18) compares the voltage with the excitation voltage. A second winding (12) connected in series opposition to the dirst winding is also connected to the comparison circuit in order to determine polarity. The voltage developed across a load resistor (16) is rectified (20) and enables the direction of the direct current flow to be determined.