The non-contact voltage and magnetic field tester is designed to detect alternating current voltage at outlets and cables, as well as magnetic fields. The Voltcraft MS-540 can identify both. In addition to alternating voltage, the tester can also check the functionality of current-carrying coils, such as those found in relays or solenoid valves.

The tester is specified according to the highest safety class CAT IV 1000 V. It operates without contact, meaning there is no need for direct contact with the test object. As a result, housings usually do not need to be opened.

The built-in antenna at the tip only responds to the phase and not to the neutral conductor. There are two adjustable sensitivity levels. When an electrical alternating field is detected, the test tip begins to glow red or blink rapidly, depending on the measurement range, the device vibrates, and an audible signal is emitted. When a magnetic field is detected, the test tip glows yellow. In the case of simultaneous detection of electrical fields and magnetic fields, the yellow and red LEDs alternate in lighting up.

The MS-540 is designed so that rain and snow, or even a water jet, will not cause it to malfunction. It can be used and stored in locations with high humidity, such as operational areas, machine rooms, and not completely dry garages, without any issues.

The housing and all control elements are constructed to be completely dustproof. Even after many years, the tester remains as functional as it was on the first day.

By pressing a button, a white LED lights up at the front, allowing the measurement point to be illuminated. This function also helps to find the way to the fuse box in dark rooms.