Method for operating a measuring system with a measuring tube, a liner, a shield, a property measuring device and a flowmeter, wherein the measuring tube has a measuring tube interior along a measuring tube longitudinal axis, wherein the measuring tube interior is lined with the liner and the liner electrically insulates the measuring tube from a medium in the measuring tube interior and protects it from wear by the medium, wherein the shielding shields the measuring tube interior from external interference, wherein the property measuring device comprises a property measurement controller and at least three property measurement electrodes and the at least three property measurement electrodes are arranged in a first region of the measuring tube interior on the measuring tube, wherein the flowmeter has a flow measurement controller, a magnetic field generator and at least two flow measurement electrodes, and the magnetic field generator and the at least two flow measurement electrodes are arranged on the measuring tube in a second region, different from the first region, of the measuring tube interior, wherein the flow measurement controller and the property measurement controller are connected to each other via a signal line, wherein the property measurement controller first carries out a number of impedance measurements with the at least three property measurement electrodes on the medium in the first region over an impedance measurement period and, at the same time, the impedance measurement period is signaled by a measuring signal via the signal line to the flow measurement controller and then at least one property of the medium is determined from the impedance measurements using impedance tomography, and wherein a magnetic field is generated in the medium in the second region by the flow measurement controller using the magnetic field generator, a number of voltage measurements are carried out at a sampling rate using the at least two flow measurement electrodes on the medium in the second region, the impedance measurement duration is taken from the measuring signal by the flow measurement controller, the voltage measurements carried out during the impedance measurements are discarded, and a flow rate of the medium is determined from the remaining voltage measurements. wherein the measuring tube has a measuring tube interior along a measuring tube longitudinal axis, wherein the measuring tube interior is lined with the liner and the liner electrically insulates the measuring tube from a medium in the measuring tube interior and protects it from wear by the medium, wherein the shielding shields the measuring tube interior from external interference, wherein the property measuring device comprises a property measurement controller and at least three property measurement electrodes and the at least three property measurement electrodes are arranged in a first region of the measuring tube interior on the measuring tube, wherein the flowmeter has a flow measurement controller, a magnetic field generator and at least two flow measurement electrodes, and the magnetic field generator and the at least two flow measurement electrodes are arranged on the measuring tube in a second region, different from the first region, of the measuring tube interior, wherein the flow measurement controller and the property measurement controller are connected to each other via a signal line, wherein the property measurement controller first carries out a number of impedance measurements with the at least three property measurement electrodes on the medium in the first region over an impedance measurement period and, at the same time, the impedance measurement period is signaled by a measuring signal via the signal line to the flow measurement controller and then at least one property of the medium is determined from the impedance measurements using impedance tomography, and wherein a magnetic field is generated in the medium in the second region by the flow measurement controller using the magnetic field generator, a number of voltage measurements are carried out at a sampling rate using the at least two flow measurement electrodes on the medium in the second region, the impedance measurement duration is taken from the measuring signal by the flow measurement controller, the voltage measurements carried out during the impedance measurements are discarded, and a flow rate of the medium is determined from the remaining voltage measurements.