The AEMC Instruments Model 6255 is a rugged, portable 10kV digital insulation resistance tester, more commonly known as a megohmmeter. It is a high-end diagnostic instrument designed to accurately measure very high electrical resistance values to assess the quality and integrity of insulation in electrical equipment.
High Test Voltage: Capable of generating multiple fixed test voltages, including 500V, 1000V (1kV), 2500V (2.5kV), 5000V (5kV), and 10,000V (10kV).
Programmable Test Voltage: Allows the user to select custom test voltages in steps from 40V to 10kV.
Extremely Wide Measurement Range: Can measure insulation resistance from 10kΩ up to 25TΩ (Tera-ohms).
The Model 6255 is used for testing the insulation quality of a wide range of high-voltage electrical apparatus, including:
Cables: Verifying the integrity of power and control cable insulation.
Transformers: Testing windings and bushings.
Motors and Generators: Assessing the insulation of motor windings.
Switchgear: Testing circuit breakers, busbars, and other components.
Insulators and Bushings: Measuring for contamination or degradation.
| Feature | Specification |
| Test Voltages (Fixed) | 500V, 1000V, 2500V, 5000V, 10,000V |
| Test Voltages (Variable) | 40V to 10kV (programmable) |
| Insulation Resistance Range | 10 kΩ to 25 TΩ |
| Automatic Calculations | DAR (Dielectric Absorption Ratio), PI (Polarization Index), DD (Dielectric Discharge) |
| Data Storage | Up to 80,000 measurements |
| Interface | USB, Optically Isolated |
| Power Source | Rechargeable NiMH Battery Pack; can also be operated while connected to AC power. |
| Safety Rating | 1000V CAT IV |
Automatic Diagnostic Tests: This is a key feature for modern insulation testing. The 6255 automatically calculates and displays critical diagnostic ratios:
- DAR (Dielectric Absorption Ratio): Compares the resistance reading at 60 seconds to the reading at 30 seconds
- PI (Polarization Index): Compares the resistance reading at 10 minutes to the reading at 1 minute. These time-based tests provide a deeper insight into the condition of the insulation, helping to identify moisture or contamination.
Advanced Testing Modes:
- Step Voltage Test: Applies test voltage in increasing steps over time to reveal insulation weaknesses that may not be apparent at a single voltage.
- Ramp Test: Smoothly ramps the test voltage up to a pre-programmed level while graphing the current vs. voltage.
- Data Storage and Analysis: It has a large internal memory to store test results. The stored data can then be downloaded to a computer via USB using AEMC’s DataView® software for detailed analysis and report generation.
Safety Features:
Automatic Discharge: Automatically and safely discharges the equipment under test after the measurement is complete.
High Safety Rating: Rated to 1000V CAT IV.
Alarms: Programmable alarms to alert the user when a certain resistance or time threshold is met.
User Interface: Features a large, graphical LCD screen that can simultaneously display the resistance measurement, test voltage, timer, and a real-time graph of the test.
