A measuring device that operates according to a radar principle and/or according to the principle of the guided microwave, the device comprising: a container for holding a first liquid and a second liquid of lower density than the first liquid, and comprising a first sub-region, a second sub-region and one or several connections (603, 604) between the two sub-regions (601, 602) for exchanging liquid between the two sub-regions (601, 602); a first measuring apparatus for acquiring a first echo curve that illustrates the reflection conditions within the first sub-region; a second measuring apparatus for acquiring at least one second echo curve that illustrates the reflection conditions within the second sub-region; an evaluation unit; wherein the evaluation unit is designed for determining a first electrical distance to the surface of the second liquid in the first sub-region with the use of the first echo curve; wherein the evaluation unit is designed for determining a second electrical distance to a separating layer between the two liquids in the first sub-region with the use of the first echo curve; wherein the evaluation unit is designed for determining a third electrical distance to the surface of the second liquid in the second sub-region with the use of the second echo curve, wherein the first electrical distance differs from the third electrical distance; wherein the evaluation unit is designed for determining at least one characteristic value relating to the position of an actually existing or a virtual separating layer between two different liquids in the second sub-region, or for determining at least one characteristic value relating to the composition of the mixture comprising the two different liquids; wherein the evaluation unit is designed for determining the position of an actually existing or a virtual separating layer in the second sub-region, or for determining the characteristic value relating to the composition of the mixture comprising the two different liquids, which uses the first, the second and the third electrical distance and the density ratio of the two liquids; wherein the first sub-region and the connections (603, 604) between the two sub-regions (601, 602) are designed in such a manner that, when a defined quantity of liquid is added in the second sub-region, the level of a liquid column forming in the first sub-region differs from the level of a liquid column in the second sub-region. a container for holding a first liquid and a second liquid of lower density than the first liquid, and comprising a first sub-region, a second sub-region and one or several connections (603, 604) between the two sub-regions (601, 602) for exchanging liquid between the two sub-regions (601, 602); a first measuring apparatus for acquiring a first echo curve that illustrates the reflection conditions within the first sub-region; a second measuring apparatus for acquiring at least one second echo curve that illustrates the reflection conditions within the second sub-region; an evaluation unit; wherein the evaluation unit is designed for determining a first electrical distance to the surface of the second liquid in the first sub-region with the use of the first echo curve; wherein the evaluation unit is designed for determining a second electrical distance to a separating layer between the two liquids in the first sub-region with the use of the first echo curve; wherein the evaluation unit is designed for determining a third electrical distance to the surface of the second liquid in the second sub-region with the use of the second echo curve, wherein the first electrical distance differs from the third electrical distance; wherein the evaluation unit is designed for determining at least one characteristic value relating to the position of an actually existing or a virtual separating layer between two different liquids in the second sub-region, or for determining at least one characteristic value relating to the composition of the mixture comprising the two different liquids; wherein the evaluation unit is designed for determining the position of an actually existing or a virtual separating layer in the second sub-region, or for determining the characteristic value relating to the composition of the mixture comprising the two different liquids, which uses the first, the second and the third electrical distance and the density ratio of the two liquids; wherein the first sub-region and the connections (603, 604) between the two sub-regions (601, 602) are designed in such a manner that, when a defined quantity of liquid is added in the second sub-region, the level of a liquid column forming in the first sub-region differs from the level of a liquid column in the second sub-region.