Secuload N adapter - Why do different measurement results occur depending on the connection to its blue sockets?

Basically, it is irrelevant to which of the SECULOAD N's blue connections the positive or negative pole of the welding circuit to be tested is connected, as long as the voltage measurement at the output (red and black socket) is not earth-related.

Measurement results may differ if both the welding circuit and the voltage measurement circuit have a low insulation impedance to protective earth.
The different measurement results are due to the different input impedances of the upper and lower blue connection of the SECULOAD.
Note: A low-resistance protective conductor connection of both the welding circuit and the measuring circuit can lead to the destruction of the SECULOAD N.

The lower blue socket should always be connected to the negative pole of the welding device to be tested.