Measuring circuit for determining capacitances and resistances - is operation by compensating measuring bridges balanced by hand

摘要

After the switch (9) has been opened, the capacitance (Cx) discharges through the resistor (R). The discharge current flows through an impedance converter (1) and then flows to two comparators (2a) and (2b) connected in parallel. These comparators produce a time signal propositional to the capacitance. A switching arrangement for the measuring circuit ensures that a balancing of parasitic input capacitances is achieved by the adjustable pulse delay circuit (3). In an alternative version of the measuring circuit, the discharge of definite capacitances (C) with unknown resistances (Rx) can be used to measure the value of the resistances. The counter (7) receives signals from a control device (8) connected to the relay coil of the switch (9). The counter is connected to gates (5) and (4).