TTR-400
The TTR-400 is a portable transformer turns ratio meter that measures turns ratio, voltage ratio and phase displacement…
- Ratio range 0.9 – 10000
- Accuracy (by ratio range) ±0.1 % / ±0.2 % / ±0.5 %
- Test voltage 0 – 160
TWO-1100S
Transformer Winding Ohmmeter
High-current 4-wire winding resistance meter with DC test current up to 100 A — measures 30 µΩ–4 Ω with ±0.2 % reading accuracy for transformer and rotating-machine windings.
Max. test current
100
Resistance range
30 µΩ – 4 Ω
Accuracy
±0.2 % rdg ± 2 µΩ
Resolution
0.1
Method
4-wire (Kelvin)
Weight
19.5
Overview
Technical Specifications
| Specification | Value | Unit |
|---|---|---|
| DC output range | 100 A · 50 A · 20 A · 10 A · 5 A (user-selectable maximum) | |
| Measuring range @ 100 A | 30 µΩ – 100 mΩ | |
| Measuring range @ 50 A | 100 µΩ – 200 mΩ | |
| Measuring range @ 20 A | 200 µΩ – 1 Ω | |
| Measuring range @ 10 A | 500 µΩ – 2 Ω | |
| Measuring range @ 5 A | 2 mΩ – 4 Ω | |
| Measuring accuracy | ±0.2 % reading ± 2 µΩ | |
| Resolution | 0.1 | µΩ |
| Method | 4-wire (Kelvin) | |
| Display | 320 × 240 colour LCD | |
| Memory capacity | 1000 test results | |
| Data download | USB port | |
| Printing | Built-in printer | |
| Discharge | Fast automatic safety-discharge circuit | |
| Protection functions | Overcurrent · overvoltage · discharge | |
| Power supply | Customized AC 220 V / 230 V ±10 %, 50/60 Hz (optional) | |
| Operating temperature | −10 … +50 | °C |
| Storage temperature | −20 … +60 | °C |
| Humidity | < 90 % | |
| Dimensions | 400 × 225 × 350 | mm |
| Weight | 19.5 | kg |
| Safety | Designed in accordance with IEC 61010-1 | |
| EMC | Light industrial IEC 61326 | |
Key Features
4-wire (Kelvin) measurement
Separate current and sense leads exclude test-lead resistance — essential for accurate milliohm-level winding measurement.
DC test current up to 100 A
User-selectable 100 / 50 / 20 / 10 / 5 A ranges to magnetize the core for a fast, stable reading.
Wide resistance range
Measures from 30 µΩ to 4 Ω across the selectable current ranges.
High accuracy & resolution
±0.2 % reading ± 2 µΩ accuracy with 0.1 µΩ resolution.
Fast automatic safety discharge
Safely dissipates the stored magnetic energy of inductive windings after each test.
Comprehensive protection
Overcurrent, overvoltage and discharge protection for operator and instrument safety.
Results storage, print & download
1000-test-result on-board memory, built-in printer and USB download for record keeping.
Clear colour display
320 × 240 colour LCD provides straightforward, readable results in the field.
Applications
Transformer winding-resistance testing
DC resistance measurement of power and distribution transformer windings across all phases and tap positions.
Rotating machines & reactors
Winding-resistance measurement of motors, generators and reactors.
Connection & joint verification
Detection of loose or high-resistance connections, brazed/soldered joints and conductor faults.
OLTC contact assessment
Resistance comparison across tap positions to evaluate on-load tap-changer contact condition.
Low-current circuit resistance
Resistance measurement of connections, contacts and control circuits at low current.
Frequently Asked Questions
Why is a high test current used for winding-resistance measurement?
Transformer windings are inductive. A high DC test current drives the core into a defined magnetizing state so the inductive time constant is minimized and the resistance reading stabilizes quickly. Higher currents also give better resolution on low-resistance, high-rated-power windings.
Which test current should I choose?
Start from the highest current the winding and tap can safely carry, then confirm the reading is within the current's specified resistance range. The TWO-1100S offers 100 / 50 / 20 / 10 / 5 A; lower currents are used for high-resistance windings or when the test current must be limited.
How does the 4-wire method improve accuracy?
Two leads carry the test current and two separate leads sense the voltage across the winding. Because the sense leads carry negligible current, the resistance of the test leads themselves is excluded from the result — critical when measuring milliohm-level winding resistance.
Is it safe to disconnect the test leads after a measurement?
No — a transformer winding stores magnetic energy during the test. The TWO-1100S has a fast automatic safety-discharge circuit that dissipates this energy after the test. Always wait for the discharge to complete before disconnecting the leads.
Downloads
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