Portable insulation resistance meter GM series

The GM-20kV Adjustable High-Voltage Digital Test Set is a portable insulation resistance tester that measures insulation resistance with selectable test voltages up to 0 / 5 / 10 / 20 kV. It combines I→V conversion and the division function of a dual-integral digital voltmeter to display insulation resistance values directly on the LCD.

Functions and key principles

• Selectable test voltages: 0, 5, 10 and 20 kV generated by a feedback-type DC/DC converter.
• Measurement method: current-ratio meter equivalent to a traditional megohmmeter; ohm-to-digital conversion via I→V conversion and division by a dual-integral digital voltmeter.
• Display: 3½-digit LCD meter heads showing test voltage, resistance and time.
• Power supply: internal rechargeable battery (lithium or NiMH noted for maintenance); DC15V dedicated adapter for charging; typical continuous operation 6–8 hours after full charge (charging time ~6–8 hours).
• Timing and alarms: stopwatch up to 19 minutes 59 seconds (20-minute cycle); audible signals at 15 s, 60 s and each minute; short beep and 3 s hold of resistance reading at programmed points; continuous alarm if measurement is out of range or invalid.

Working principle
The instrument generates DC high voltage from its internal battery via a DC/DC converter and applies it across the tested object from the E terminal to the L terminal. The resulting current is converted I→V, divided and then processed by the digital voltmeter to display the insulation resistance value directly on the LCD. The design uses medium-to-large-scale integrated circuits to provide high output power and high short-circuit current capability with multiple output levels.

Precautions

• Safety: terminal 'L' is the high-voltage output; terminal 'E' must be grounded.
• Before applying high voltage, inspect the instrument and connect the load resistor before switching on to avoid sparking or discharge that may damage internal circuits or standard resistors.
• Battery charging uses a constant-voltage, current-limited method; full charge takes about 6–8 hours. Recharge periodically (recommended every three months) if stored long-term to preserve battery life.
• Battery replacement: when replacing NiMH cells, select cells with similar capacity and fully charge each cell before assembly.

Associated images & documents

• Product image gallery (product views and technical illustrations) available on the product page.
• User manual and calibration certificate available as PDF documents.

Technical specifications

• Test voltages: 0 / 5 / 10 / 20 kV (selectable)
• Measurement method: I→V conversion + division via dual-integral digital voltmeter (current-ratio meter)
• Electric field interference immunity: 2 mA (50/60 Hz)
• Timing and alarm: stopwatch up to 19:59 (20 min cycle); alarms at 15 s, 60 s and each minute; hold reading 3 s; continuous alarm on invalid/low readings
• Display: 3½-digit LCD for voltage, resistance and time
• Power: built-in rechargeable battery; DC15V charging via dedicated adapter
• Operating environment: -20 °C to +40 °C; relative humidity 20%–90%
• Dimensions (L×W×H): 315 × 240 × 180 mm
• Weight: 5.5 kg
• Alternate names: Insulation Resistance Tester; Insulation Meter; Adjustable High Voltage Digital Tester