A current-to-voltage converter for 5 A to 5 V and 30 Hz to 30 kHz

A current-to-voltage converter (CVC) is presented, which has three input ranges for nominal input currents of 0.2, 1, and 5 A with frequencies from 30 Hz to 30 kHz. The converter uses an amplifier-aided two-stage current transformer which operates with a very small number of ampere-turns and the primary (measurement) current path of which may be potentially elevated without its error characteristics being affected. The secondary current of 5 mA of the transformer is converted into voltage using an inverting amplifier with a feedback resistor of 1 kΩ. By fine adjustment of its frequency-dependent feedback, small errors and a small error variation are achieved over the whole frequency range. The variation of errors between 20 and 100% of nominal current in each current range is negligibly small. In the frequency range from 30 Hz to 1 kHz, relative errors of less than 10^-4±2×10^-5 are achieved. From 1 to 30 kHz, the errors increase up to 2×10^-4 with ±5×10^-5 uncertainty for the in-phase and ±40×10-5 for the quadrature component. The current-to-voltage converter was calibrated by means of a high-quality current shunt, which was especially developed for this purpose