Capacitance and Inductance Tester is a professional device used in the field of power systems and electronic engineering to measure passive components such as capacitors and reactors (inductors). It can not only measure basic capacitance (C) and inductance (L) values, but also typically measure key indicators such as dissipation factor (tanδ) and equivalent series resistance (ESR), making it an important tool for evaluating equipment insulation condition and performance.



Depending on the application scenario, these instruments are mainly divided into power system specific types (focusing on high voltage, large capacity, on-site without disconnecting lines) and precision electronic types (focusing on high frequency, high precision, small components).

⚙️ Core Working Principle

Although technical details vary among different models, mainstream testers are typically based on the following principles:

Bridge Circuit and Vector Measurement Method:

This is the core of power-type testers. The instrument internally generates a stable sinusoidal AC signal (excitation source) applied to the component under test. It synchronously collects voltage and current signals through high-precision voltage and current sensors (such as clamp-type current transformers).

Calculation Logic: Using the formula 

to distinguish capacitive (current leads voltage by 90°) or inductive (current lags voltage by 90°) characteristics, thereby accurately calculating capacitance or inductance values.

Heterodyne Anti-Interference Technology:

In strong electromagnetic interference environments such as substations, power frequency (50Hz) interference can seriously affect measurement accuracy. Modern instruments typically use heterodyne power supplies (such as 45Hz, 55Hz, 60Hz, etc.) for testing, combined with digital filtering algorithms to effectively strip on-site interference and ensure data accuracy.

Main Functions and Features

Table

Function Dimension    Detailed Description

Non-disconnect Measurement    The core advantage of power-type instruments. Using a clamp-type ammeter combined with voltage sampling, it can measure the capacitance of a single capacitor without disconnecting the capacitor bank's connecting wires (star or delta connection), greatly improving on-site maintenance efficiency.

Multi-parameter Testing    In addition to capacitance (C) and inductance (L), it can also measure dielectric loss (tanδ), impedance (Z), phase angle, resistance (R), etc., to comprehensively assess component health.

Automatic Identification    The instrument can automatically determine whether the component under test is a capacitor or inductor, and automatically switch ranges and calculation models, simplifying the operation process.

Data Processing    Equipped with large-capacity storage, it can save historical test data, support USB export or on-site printing, facilitating the generation of test reports.

Detection of Reactive Power Compensation Devices in Power Systems:

Used for regular inspections and preventive tests of parallel capacitor banks and reactors in substations and distribution rooms.

Detect faults such as bulging, oil leakage, internal component breakdown or open circuit in capacitors.

Research and Production of Electronic Components:

Used to measure precise parameters of components such as ceramic capacitors, electrolytic capacitors, and chip inductors (LCR testing), typically using high-precision LCR digital bridges.

CVT (Capacitive Voltage Transformer) Testing:

Some high-end models support CVT ratio and dielectric loss testing.

 Typical Technical Parameters (Reference)

Indicators vary among different models; the following are common parameter ranges for power-type testers:

Capacitance measurement range: 0.1μF to 20,000μF (or higher)

Inductance measurement range: 1mH to 20H

Measurement accuracy: typically around ±1% (depending on range)

Working power supply: AC 220V or built-in lithium battery (for outdoor operation without power supply)