Measuring system, comprising: a first pipe branch through which a medium flows in a predefined flow direction, a measuring device which is arranged in the first pipe branch and through which the medium flows, wherein said device is designed to determine and/or monitor the flow and/or the viscosity of the medium, wherein said measuring device has a predefined nominal diameter, and a preparation system arranged in the predefined flow direction in the first pipe branch upstream from the measuring device, - with a pressure increase unit designed to increase the pressure of the medium in the first pipe branch, comprising: a pump arranged in a pump section of the first pipe branch; and a first non-return valve, which is arranged in a first section of the first pipe branch which is parallel to the pump section, wherein medium can only flow through the first non-return valve in the event that a first predefined target pressure is reached and only in a direction opposite to the predefined flow direction; and - with a temperature regulation unit designed to regulate the temperature of the medium in the first pipe branch, said unit comprising: at least a heat element, at least a first temperature measuring device (13,...) and a control/evaluation unit connected to the heat element and to the first temperature measuring device, characterized in that the preparation system has a second non-return valve, which is arranged in a second section of the first pipe branch parallel to the pump section, and wherein medium can flow through said valve in the event that a second predefined target pressure is reached and only in the flow direction, wherein the second predefined target pressure is less than the first predefined target pressure, particularly by at least a factor of 5. a first pipe branch through which a medium flows in a predefined flow direction, a measuring device which is arranged in the first pipe branch and through which the medium flows, wherein said device is designed to determine and/or monitor the flow and/or the viscosity of the medium, wherein said measuring device has a predefined nominal diameter, and a preparation system arranged in the predefined flow direction in the first pipe branch upstream from the measuring device, - with a pressure increase unit designed to increase the pressure of the medium in the first pipe branch, comprising: a pump arranged in a pump section of the first pipe branch; and a first non-return valve, which is arranged in a first section of the first pipe branch which is parallel to the pump section, - with a pressure increase unit designed to increase the pressure of the medium in the first pipe branch, comprising: a pump arranged in a pump section of the first pipe branch; and a first non-return valve, which is arranged in a first section of the first pipe branch which is parallel to the pump section, wherein medium can only flow through the first non-return valve in the event that a first predefined target pressure is reached and only in a direction opposite to the predefined flow direction; and - with a temperature regulation unit designed to regulate the temperature of the medium in the first pipe branch, said unit comprising: at least a heat element, at least a first temperature measuring device (13,...) and a control/evaluation unit connected to the heat element and to the first temperature measuring device, characterized in that the preparation system has a second non-return valve, which is arranged in a second section of the first pipe branch parallel to the pump section, and wherein medium can flow through said valve in the event that a second predefined target pressure is reached and only in the flow direction, wherein the second predefined target pressure is less than the first predefined target pressure, particularly by at least a factor of 5. - with a temperature regulation unit designed to regulate the temperature of the medium in the first pipe branch, said unit comprising: at least a heat element, at least a first temperature measuring device (13,...) and a control/evaluation unit connected to the heat element and to the first temperature measuring device, characterized in that the preparation system has a second non-return valve, which is arranged in a second section of the first pipe branch parallel to the pump section, and wherein medium can flow through said valve in the event that a second predefined target pressure is reached and only in the flow direction, wherein the second predefined target pressure is less than the first predefined target pressure, particularly by at least a factor of 5. at least a heat element, at least a first temperature measuring device (13,...) and a control/evaluation unit connected to the heat element and to the first temperature measuring device, characterized in that the preparation system has a second non-return valve, which is arranged in a second section of the first pipe branch parallel to the pump section, and wherein medium can flow through said valve in the event that a second predefined target pressure is reached and only in the flow direction, wherein the second predefined target pressure is less than the first predefined target pressure, particularly by at least a factor of 5.