A junction measurement box, configured for being mounted on a photovoltaic solar module, comprising: a housing having a support section formed for being supported on the solar module, a circumferential side wall, and a lid; string line feedthroughs and/or string line connectors; characterized in that the junction measurement box comprises a string current measuring module including a measuring component (30, 30a, 30b, 30c) and an evaluation device for measuring the string current in the junction measurement box; wherein the junction measurement box further comprises a measurement box connection line for connecting the junction measurement box to a junction and connection box of the solar module, or a measurement box plug-in connector that allows the junction measurement box to be directly plugged to the junction and connection box, so that the junction measurement box and the junction and connection box are embodied as separate boxes, each one with its own housing for being mounted on the same photovoltaic solar module; OR wherein the junction measurement box further comprises a junction and connection device for electrically contacting conductor strips of the solar module on one side and for producing junctions and connections with the string line (10, 12) or a box string line (22, 24) on the other side, in order to establish the electrical connection between the conductor strips and the string lines (10, 12) when the junction measurement box is mounted on the solar module for delivering the electrical power generated by the solar module, so that the junction measurement box at the same time defines the junction and connection box of the solar module. a housing having a support section formed for being supported on the solar module, a circumferential side wall, and a lid; string line feedthroughs and/or string line connectors; characterized in that the junction measurement box comprises a string current measuring module including a measuring component (30, 30a, 30b, 30c) and an evaluation device for measuring the string current in the junction measurement box; wherein the junction measurement box further comprises a measurement box connection line for connecting the junction measurement box to a junction and connection box of the solar module, or a measurement box plug-in connector that allows the junction measurement box to be directly plugged to the junction and connection box, so that the junction measurement box and the junction and connection box are embodied as separate boxes, each one with its own housing for being mounted on the same photovoltaic solar module; OR wherein the junction measurement box further comprises a junction and connection device for electrically contacting conductor strips of the solar module on one side and for producing junctions and connections with the string line (10, 12) or a box string line (22, 24) on the other side, in order to establish the electrical connection between the conductor strips and the string lines (10, 12) when the junction measurement box is mounted on the solar module for delivering the electrical power generated by the solar module, so that the junction measurement box at the same time defines the junction and connection box of the solar module.