Voltage divider with variable division ratio - has AC test voltage applied to divider to control variable resistance

摘要

The division ratio is determined by a variable resistor used as a control element. DC (Ur) and AC (Ue) are applied to the input of voltage divider provided at its output with a filter (TP, C2) separating these two voltages (Ur, Ue). One of these voltages (Ue) is the voltage to be divided, and the voltage (Ur) is a constant amplitude test voltage. Output from the latter (TP) is applied, possibly through a rectifier to the first input of a differential amplifier (3). A variable control voltage (UF) whose amplitude is smaller than that of voltage (Ur), is applied to the amplifier second input. The variable resistor is set to such a resistance by the amplifier (3) output, that differential amplifier input voltages are as equal as possible. The variable resistor has about the same resistance for DC and AC.