Insulation Resistance Tester, commonly known as "megger" or "megohmmeter", is the core tool for insulation performance testing of electrical equipment and lines in power and electrical systems. It outputs high-voltage DC, measures the leakage current of the tested object under high voltage, and calculates the insulation resistance value to determine whether the equipment is damp, aged, or has insulation defects. Combined with the latest market data and industry evaluations in 2026, here is an in-depth guide to insulation resistance testers: 1. Core Classification and Technical Indicators According to application scenarios and voltage levels, they are mainly divided into two categories: Traditional hand-cranked type: gradually being phased out, only used in extreme environments without power supply. Digital type (mainstream): Voltage levels: common specifications include 250V, 500V, 1000V, 2500V, 5000V, 10000V. Low-voltage equipment (<500V): choose 500V or 1000V range. High-voltage equipment (10kV and above): usually requires 2500V or 5000V range. Ultra-high voltage / large transformers / cables: requires 5000V or 10000V range. Key functions: PI (Polarization Index) & DAR (Dielectric Absorption Ratio): automatically calculated and recorded to determine the degree of insulation dampness (this is the key to distinguishing high-end from low-end instruments). Step voltage test: automatically switches between multiple voltage levels to evaluate insulation nonlinear characteristics. Filtering and anti-interference: maintains stable readings in strong electromagnetic fields (such as substations). Safe discharge: automatically discharges the tested object after the test to protect operators. 2. Top 10 Brand Rankings in 2026 (comprehensive CNPP, MAIGOO, and industry reputation) According to major authoritative rankings updated in February 2026, the market pattern shows a trend of "imported brands dominate high-end, domestic brands offer cost-effective alternatives": First tier: International top brands (high precision, high reliability, high price) These brands are commonly used in foreign-related projects, scientific research laboratories, and occasions requiring high data authority. Megger - UK Status: the "gold standard" in insulation testing, the inventor. Its MIT series (such as MIT515, MIT1525) are industry benchmarks. Features: extremely durable, CAT IV safety rating, powerful data analysis software, but expensive (usually tens of thousands of RMB). HIOKI - Japan Status: representative of Asian high-end, known for compactness, portability, and high precision. Features: user-friendly operation, extremely strong anti-interference capability, suitable for work in narrow spaces. Fluke - USA Status: giant in general test instruments. Features: its 1587 FC and other models combine multimeter functions, support wireless transmission, suitable for multi-functional needs of field maintenance personnel. GMC INSTRUMENTS - Germany Features: European high-end brand, excels in precision measurement in complex environments. KIKUSUI / KYORITSU - Japan Features: Kyoritsu has unique advantages in combining analog and digital types, with high cost-effectiveness; Kikusui excels in safety testing integration. Second tier: Leading domestic brands (high cost-effectiveness, fast service, full features) With technology maturity, domestic brands have taken a dominant position in power maintenance and factory inspection. 6. UNI-T * Features: domestic instrument leader, extremely wide product line. Its UT500 series has huge sales in civil and industrial general use, with extremely high cost-effectiveness. 7. VICTOR * Features: established domestic instrument brand, good durability, nationwide after-sales network, suitable for grassroots electricians and routine maintenance. 8. Tonghui * Features: focuses on electronic measuring instruments, its insulation resistance testers perform outstandingly in laboratories and precision manufacturing. 9. Ainuo * Features: deep accumulation in safety testing and specialized high-voltage testing. 10. Other professional power brands: such as Wuhan UHV, Shanghai Shenggao, etc. (refer to the previous loop resistance tester brands), in terms of 5kV/10kV high-power insulation testers for power systems (such as transformers, GIS), these professional manufacturers often have more advantages than general instrument manufacturers. (Note: some lists such as "Anli Touch" and "Jinguan Electric" mainly appear in specific niche or emerging voting lists; when purchasing, verify their specific qualifications and market share.) 3. New Industry Trends in 2025-2026 Intelligence and Internet of Things (IoT): new instruments generally come standard with Bluetooth/WiFi, test data can be uploaded in real-time to mobile apps or cloud management systems, automatically generating electronic reports that meet State Grid/Southern Grid standards, reducing manual entry errors. Large-capacity batteries and fast charging: abandoning traditional dry batteries or bulky lead-acid batteries, fully adopting lithium-ion batteries, supporting long continuous testing and fast charging. Multi-parameter integration: one instrument simultaneously has insulation resistance, polarization index, dielectric loss (some high-end), and even leakage current testing functions, achieving "multi-function in one machine". Safety upgrades: enhanced automatic discharge logic for capacitive loads (such as long cables) to prevent residual high voltage from harming people; shell protection rating generally reaches IP65 or even IP67, suitable for harsh outdoor weather. 4. Selection and Usage Recommendations Select by voltage level: 380V motor/line -> choose 500V/1000V range. 10kV switch/cable -> choose 2500V/5000V range. 35kV and above main transformer/long cable -> must choose 5000V/10000V with high output power (otherwise charging time is too long, unable to measure accurately). Pay attention to short-circuit current: high-quality instruments should have short-circuit current ≥1mA (or even 5mA) to ensure charging speed for large capacitive test objects. Operating specifications: Power off and verify: before testing, confirm that the equipment is powered off and fully discharged. Correct wiring: L connects to the line, E connects to ground, G connects to the shielding ring (to eliminate surface leakage effects, especially important when measuring cables). Reading timing: read values at 15 seconds (R15) and 60 seconds (R60) to calculate the absorption ratio, or 1 minute and 10 minutes to calculate the polarization index. Discharge after testing: after the test, ensure the instrument automatically discharges or manually discharge, and only after confirming no voltage can you disconnect the wires. If you need specific model recommendations for specific equipment (such as "110kV transformer" or "photovoltaic DC cable"), please let us know
