Digital LCR Meter Principle and Core Function A digital LCR meter measures inductance, capacitance, and resistance by applying a predetermined test signal to the component. An LCR function switch selects the required parameter, and a 1 kHz oscillator generates the test signal with automatic gain control. The process relies on simultaneously measuring the voltage across and the current through the component to determine its value.
Test Signal Application and Voltage Measurement A controlled 1 kHz test signal is generated and sent through a source resistor to the component, establishing a voltage proportional to the applied input (E1). Simultaneously, the current flowing through the component is converted into a proportional voltage (E2) using an operational amplifier. These voltages encapsulate the primary electrical response needed for measurement.
Impedance-Based Signal Conditioning and Comparison The resistor values (RS and RR) are chosen based on the component’s impedance, with high RS used for low-impedance inductors and low RS for high-impedance capacitors. The voltages E1 and E2 are processed through a differential amplifier and control switch that determines the larger and smaller signals. The higher voltage is routed to averaging circuitry while the lower one is directed to phase-sensitive detection, preparing the signals for further analysis.
Phase Synchronization, Digital Integration, and Display Phase-locked loops and voltage-controlled oscillators generate clock signals that are phase-shifted by 90° or 270° to align with the reference signal. The outputs from the phase-sensitive detector and averaging block are fed into a digital integrator that steadily adjusts the measurement output. The final processed value is displayed on a four-digit LED display with automatic decimal placement, ensuring an accurate readout of the component under test.