UNI-T UT255B High Voltage Clamp Ammeters
The UNI-T UT255B is a robust, handheld clamp ammeter engineered for live-line measurement of AC line and leakage currents on high-voltage systems up to 60 kV. Its integrated clamp-type current transformer and guide zone allow a single-handed, non-intrusive encirclement of conductors—eliminating the need to de-energize circuits—while a set of high-strength insulation rods provides safe separation between the operator and energized components. Unlike its predecessor, the UT255B incorporates a built-in 433 MHz wireless transmitter and companion receiver that deliver real-time measurement data up to 20 meters away, enabling technicians to monitor readings from a safe distance without interrupting field operations.
Designed around the latest CT and electromagnetic-screening technologies, the UT255B delivers high accuracy down to microampere-level currents, making it particularly effective for identifying incipient insulation faults or moisture ingress in surge arresters. Its ergonomic housing balances light weight with rugged durability, ensuring stable performance in harsh outdoor environments. An intuitive interface guides users through peak-hold, data-hold, and memory-save functions, allowing transient spikes or low-level leakage currents to be captured and reviewed later.
The clamp mechanism itself can be quickly released by a simple rod-retraction action, streamlining repeated measurements along long transmission runs. By marrying precise low-current sensing, wireless data transmission, and high-voltage insulation safety, the UT255B stands as a versatile diagnostic tool for power-system maintenance teams.
Features:
- Auto-range
- 2×/s sampling rate
- Peak-hold function
- Manual range selection
- RS-232 data interface
- Data-hold capability
- Over-range (“OL”) display
- Auto power-off with LCD backlight
- Low-battery indication
- Overload protection
- Automatic plug-clamp mechanism
- Data-recall function
- Test modes: clamp-CT and integration
- On-board storage of up to 99 data sets
Specifications:
| Specification | Details |
|---|---|
| Measuring Capability: | High- & low-voltage AC leakage current and on-line current indirect CT ratio measurement |
| Power Supply: | DC 6 V (4 × 1.5 V AAA alkaline batteries) |
| Measuring Modes: | General (real-time) Peak-hold, Data-hold Data-save (max 99 sets) |
| Wireless Transmission: | 433 MHz, up to 20 m range |
| Display: | 4-digit backlit LCD (suitable for dark sites) |
| LCD Size: | 47 mm × 28.5 mm |
| Dimensions: | Tester: 68 × 245 × 40 mm Receiver: 75 × 170 × 30 mm |
| Jaw Opening: | 33 mm |
| Sampling Rate: | 2 samples/sec |
| Measuring Range: | AC 0.01 mA – 600.0 A (50/60 Hz auto-range) |
| Resolution: | 10 µA |
| Accuracy: | 0.01 mA–100.0 A: ±(1% + 5 digits) 100.0 A–200.0 A: ±(2% + 5 digits) 200.0 A–600 A: ±(3% + 5 digits) |
| Data Save: | Max 99 sets MEM icon during saving FULL icon when memory is full |
| Peak-Hold: | Automatic; press PEAK to capture max value (PEAK light on) |
| Data-Hold: | Press HOLD to freeze reading (HOLD icon on) |
| Over-Range Display: | “OL A” icon |
| No-Signal Display: | “no – –” icon when receiver sees no transmission |
| Live-Circuit Capability: | Up to 60 kV with supplied insulation rod |
| Auto Power-Off: | After 15 minutes inactivity |
| Low-Battery Indication: | Icon when battery voltage < 4.8 V |
| Weight: | Tester (with batteries): 335 g Total (tester + rods + batteries): 2.5 kg |
| Insulation Rods: | 5 × 1 m sections, Ø 32 mm; withstand AC 100 kV (rod-to-housing) & AC 1 000 V (housing-to-core) |
| Operating Conditions: | –20 °C to 60 °C, ≤ 70% RH; Storage: –20 °C to 40 °C, ≤ 80% RH |
| Interference Resistance: | No shared-frequency interference at 315 MHz or 433 MHz |
Applications:
- Live-line current and leakage detection.
- Condition monitoring of zinc oxide surge arresters.
- Inspection and maintenance of high-voltage electrical systems.
- On-site diagnosis of insulation faults.
- Detection of abnormal leakage currents.
- Verification of current transformer (CT) ratios.
- Power utility and industrial field work.
Package Include:
- 1x High-Voltage Clamp Ammeter (UT255B)
- 5x Insulation Rods – 1 m sections (Ø 32 mm)
- 1x Wireless Receiver
- 4x AAA Alkaline Batteries (1.5 V LR03)
- 1x English User Manual
- 1x Gift Box / Tool Box
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