General
Display freeze time when TEST button is pressed	7 s
30 mA RCD test

The MX531 is a socket tester from the brand Metrix, specifically designed for testing 2P+E sockets in TT systems. The device is used by electricians, tradespeople, and maintenance technicians for quick and reliable checking of electrical connections, earth resistance, and the function of 30 mA RCDs. The tester is compact, easy to handle, and can be operated with one hand, with the illuminated LCD display always facing upwards regardless of insertion direction into the socket. The display changes colour depending on the test result: blue for correct connection configuration, red for errors, and grey after removal if all values are compliant.

Applications

The MX531 is intended for testing sockets in TT systems, particularly 2P+E sockets, also known as Schuko sockets. It is used in electrical installation technology to ensure compliance with standards IEC/EN 61557-1, -3 and -6, as well as IEC 61010-2-030. Testing is performed without additional power supply, as the device powers itself from the socket and automatically recharges after removal. This makes it especially suitable for mobile applications, such as maintenance or installation in residential and commercial buildings.

Functions and Equipment in Detail

The tester performs three core functions: voltage measurement and indication of conductor positions (live, neutral, earth), automatic measurement of earth resistance RE, and functional testing of 30 mA RCDs. Earth resistance measurement is carried out in the range of 3 Ω to 1999 Ω, with the measurement range automatically switching between 3 to 199.9 Ω and 180 to 1999 Ω. Resolution is 0.1 Ω in the lower range and 1 Ω in the upper range. Accuracy is ± (3% of reading + 5 digits). If earth resistance exceeds 100 Ω or 2000 Ω, the display turns red, indicating an earthing fault.

Technology Explained Simply

The MX531 measures voltage between live and neutral in the range of 100 V to 420 V (50/60 Hz) and displays an error if voltage is below 195 V or above 253 V. Voltage between live and earth is measured in the range of 195 V to 253 V. Conductor position indication is shown via a symbol, which turns red if live and neutral or live and earth are swapped. RCD testing is performed via the TEST button, with tripping time required to be under 200 ms. Testing is only carried out if earth resistance is within acceptable limits. The display remains visible for 10 seconds after removal, with values frozen for 7 seconds if the TEST button was pressed.

Compatibility and Accessories

The device is suitable for 2P+E sockets of type E and F. It features a rotatable plug head that can rotate from -90° to +180° to fit precisely into any socket. Electrical safety complies with standard EN 61010-2-030, pollution degree 2, CAT III-300 V. Operating temperature range is from -10 °C to +45 °C.

Installation and Mounting

Installation is performed by simply inserting the tester into the socket. No additional tools or settings are required. The display is immediately readable, and results are visualized through colour changes (blue/red) and symbols. The carrying loop allows convenient attachment to the wrist, improving handling during use.

Operational Advantages

The MX531 simplifies testing processes through its compact design, immediate result display, and integrated functions in a single device. Automatic range switching and colour-changing display reduce error susceptibility. Self-powered operation and automatic recharging after removal increase efficiency. The device is designed for use in TT systems and meets the requirements of relevant standards.