Micro‑ohmmeter · Test & Measurement
GPS‑4660C
Portable 20 A digital micro‑ohmmeter for transformer windings, grounding, cables and contact resistance — 4‑wire Kelvin method with maximum resolution 0.1 µΩ, 5″ colour touchscreen, printer, temperature probe and 800‑set data memory.
Constant current to 20 AResolution 0.1 µΩ±0.2% FS accuracy
4‑wire Kelvin5″ touch LCDPrinter & 800 memories
Temp probe & conversionAuto dischargeBluetooth / USB
Key features
Up to 20 A
Selectable test currents incl. 20/10/5/1 A down to 1 mA.
High resolution
0.1 µΩ resolution with ±0.2% FS accuracy.
Four‑wire Kelvin
Lead‑drop eliminated; stable low‑ohmic readings.
Touch & print
5″ colour touchscreen with built‑in thermal printer.
Memory & comms
Stores 800 sets; USB + Bluetooth connectivity.
Smart workflow
Auto discharge, alarm settings and on‑screen guidance.
Where the GPS-4660C excels
Transformer windings
Winding resistance & tap‑changer contact checks.
Grounding & bonds
Substation grounding, busbar and mechanical joints.
Contacts & switches
Low‑ohmic resistance of breakers, relays and connectors.
Cables & coils
Conductor and motor/coil resistance with temperature conversion.
Ranges & key specifications
| Parameter | Specification |
|---|---|
| Resolution | 0.1 µΩ (maximum) |
| Accuracy | ±0.2% FS (typical) |
| Resistance ranges | 1.0 µΩ – 1000.0 µΩ (20 A) · 1.00 mΩ – 50.00 mΩ (20 A) · 1.000 mΩ – 10.000 mΩ (10 A) · 10.0 mΩ – 100.0 mΩ (10 A) · 100.00 mΩ – 1000.0 mΩ (2 A) · 1.000 Ω – 10.000 Ω (200 mA) · 10.00 Ω – 100.00 Ω (20 mA) · 100.0 Ω – 1000.0 Ω (2 mA) · 1.00 kΩ – 10.00 kΩ (1 mA) · 10.00 kΩ – 100.0 kΩ / 100.0 kΩ – 1000.0 kΩ (1 mA const. V) |
| Test current | 20 A, 10 A, 5 A, 1 A, 0.1 A, 10 mA, 1 mA (max short‑circuit 20 A) |
| Method | 4‑wire Kelvin |
| Display | 5″ touch colour LCD (854 × 480) |
| Data | 800 groups; auto shutdown 5/10/15/20/25/30 min; printer function |
| Interfaces | Bluetooth, USB |
| Battery | 14.6 V, 12,000 mAh Li‑ion (status on screen; low‑voltage prompt) |
| Power consumption | Standby ~4 W (30% brightness); Measurement ≤ 100 W |
| Dimensions / mass | 277 × 227 × 153 mm; ≈ 3.1 kg (incl. battery) |
| Operating / storage | −10–40 °C, RH < 80%; storage −10–60 °C, RH < 70% |
See datasheet for full specifications and conditions.
What’s in the box
Standard accessories
- Test wires ×2
- Temperature probe
- USB communication cable
- Charger / power adapter
- Aluminium carry case
- User manual
Items may vary by configuration.
Safety & Compliance
EMC
Designed to meet IEC 61010‑4‑3 RF field immunity ≤ 1 V/m.
SAFETY
IEC 61010‑1; CAT III 600 V; automatic discharge and protection circuits.
WARRANTY
1‑year warranty (with product registration; see datasheet).
Downloads
Kelvin hookup diagrams — GPS-4660C
4-wire Kelvin — winding / conductor
 -->
<rect x='34' y='86' width='200' height='48' rx='8' fill='%23fff' stroke='%23b7d4dc' stroke-width='2'/>
<text x='40' y='80' font-size='12' fill='%23456'>Winding / conductor under test</text>
<!-- DUT terminals -->
<rect x='34' y='110' width='16' height='16' rx='3' fill='%23eaf4f7' stroke='%2399c4cf'/>
<rect x='218' y='110' width='16' height='16' rx='3' fill='%23eaf4f7' stroke='%2399c4cf'/>
<text x='36' y='106' font-size='12' fill='%23456'>A</text>
<text x='224' y='106' font-size='12' fill='%23456'>B</text>
<!-- Current leads (thick) -->
<path d='M 360 130 C 300 120 260 118 234 118' fill='none' stroke='%23ff4d4d' stroke-width='3'/>
<circle cx='234' cy='118' r='3' fill='%23ff4d4d'/>
<path d='M 360 160 C 300 170 120 122 50 118' fill='none' stroke='%23222' stroke-width='3'/>
<circle cx='50' cy='118' r='3' fill='%23222'/>
<!-- Sense leads (thin, dashed) placed inside current clips -->
<path d='M 430 130 C 380 110 300 112 228 112' fill='none' stroke='%23ffa64d' stroke-width='2' stroke-dasharray='5,4'/>
<circle cx='228' cy='112' r='3' fill='%23ffa64d'/>
<path d='M 430 160 C 380 180 130 140 44 112' fill='none' stroke='%23666' stroke-width='2' stroke-dasharray='5,4'/>
<circle cx='44' cy='112' r='3' fill='%23666'/>
<!-- Note -->
<text x='34' y='170' font-size='12' fill='%23456'>Place V leads <tspan font-weight='bold'>inside</tspan> I clips to eliminate lead drop (Kelvin).</text>
</svg>)
- Connect I+/I- to the two DUT ends.
- Clip V+/V- inside the current clips (Kelvin) for true low-ohmic readings.
- Select current (e.g., 20/10/5/1 A as appropriate), start, wait for stabilisation, then save/print.
Tip: Use higher current for very low resistances, watching temperature rise.
Contact / busbar joint — 4-point method
 -->
<path d='M 420 130 C 380 108 170 108 160 108' fill='none' stroke='%23ffa64d' stroke-width='2' stroke-dasharray='5,4'/>
<circle cx='160' cy='108' r='3' fill='%23ffa64d'/>
<path d='M 420 160 C 380 182 100 108 90 108' fill='none' stroke='%23666' stroke-width='2' stroke-dasharray='5,4'/>
<circle cx='90' cy='108' r='3' fill='%23666'/>
<text x='42' y='180' font-size='12' fill='%23456'>Place V leads either side of the joint (inside I points) to measure joint resistance only.</text>
</svg>)
- Spread I+/I- well apart from the joint to drive current through the section.
- Place V+/V- directly across the joint (inside the I points) to read **joint** resistance only.
- Repeat after tightening/cleaning to see improvement; log/print results.
Tip: Clean oxidation and use consistent bolt torque before comparing joints.
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