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S451 Transformer Ohmmeter

  • High-Precision 10A Current Output & 0.1μΩ Resolution

  • Ultra-Wide Resistance Range (0.5μΩ to 1MΩ)

  • Automated Resistance Temperature Conversion (75°C / 115°C)

  • Multi-Tiered Safety Discharge & Circuit Protection (Back-EMF / Over-Temp)

  • Built-in Diagnostic & Self-Test Routine (0.1% Accuracy Verification)

  • High-Capacity Data Storage (9,999 Datasets) & Field Connectivity

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Product Description

Measuring the DC winding resistance of high-power transformers, 3-phase motors, and inductive devices is critical for operational safety and predictive maintenance.
The S451 Transformer Ohmmeter (Winding Resistance Tester 10A) is engineered to tackle complex field testing challenges with high speed, 0.1μΩ resolution, and maximum
operator safety.


Designed as a rugged, high-performance alternative to conventional market test sets, the S451 extends its DC resistance measurement range from 0.5μΩ up to 1MΩ . This ultra-wide range
allows field engineers to test both low-resistance power windings and high-resistance instrument transformers (CT/PT) with a single, portable unit.


Key Advantages & Performance Highlights:

  • High-Precision 10A Current Output: Rapidly magnetizes heavy inductive coils with up to 10A output current to drastically shorten test duration during field diagnostics.

  • Extended 1MΩ Resistance Range: Covers a broader scope of applications, from power transformer windings to high-resistance CT/PT units and 3-phase AC motor windings.

  • Automated Impedance & Temperature Conversion: Automatically converts raw resistance readings for copper (Cu) and aluminium (Al) to standard reference
    temperatures (75° C / 115° C), eliminating manual field calculation errors.

  • Dual Safety Discharge Protection: Integrated back-EMF protection, disconnection protection, and an active discharge warning system safely dissipate stored inductive energy, providing
    clear audible alerts.

  • Built-in Diagnostic & Self-Test Routine: Features advanced anti-interference filtering and automatic self-checks (0.1% accuracy verification) to ensure stable readings even in high- noise
    substation environments.


Technical FAQ
What is a transformer winding resistance test, and why is it essential?
A transformer winding resistance test measures the DC resistance of transformer windings to detect shorted turns, loose internal connections, broken strands, or tap changer contact deterioration. Regular testing complies with IEC61010-1 standards.
How does this high-precision winding resistance tester compare to standard market test sets?
The S451 delivers benchmark-level 10A testing precision, robust noise immunity, 0.1μΩ resolution, and an extended measurement range up to 1MΩ. Fully compliant with global testing standards, the S451 features automated discharge protection and built-in temperature correction (75°C / 115°C).
How does a portable transformer ohmmeter protect operators during high-inductive energy discharge?
Stored inductive energy in large transformer coils poses severe risks. The S451 features a multi-layer safety system: Back-EMF Protection, disconnection protection, and active audio- visual discharge alarms that alert operators when it is safe to disconnect test leads.
How does the automatic temperature conversion feature work on a digital DC resistance meter?
Winding Resistance Tester 10A varies with temperature. The S451 measures ambient/winding temperature and automatically converts raw data to standard reference temperatures (75°C for Cu / 115°C for Al) using standard conversion formulas.
Can this Winding Resistance Tester 10A be used for 3-phase motor winding resistance testing?
Yes. The S451 adjustable current (up to 10A) and broad 0.5μΩ to 1MΩ range make it ideal for measuring 3-phase AC motor winding resistance, generator coils, CT/PT units, and general electrical diagnostics.