Temperature sensor arrangement for temperature measurements within a process vessel , the process vessel comprising at least two process vessel ports (300, 300', 300") at different locations of the process vessel, wherein - at or through each process vessel port (300, 300', 300") a temperature sensor assembly (400, 400', 400") is inserted into the process vessel, - each temperature sensor assembly (400, 400', 400") comprises at least one primary temperature sensor (501, 502, 503, 501', 502', 503', 501", 502"), which is positioned at a measurement location (901, 902, 903, 901', 902', 903', 901", 902") within the process vessel , and - at least one of the temperature sensor assemblies (400, 400', 400") comprises at least one secondary temperature sensor (601, 602, 601', 602', 603', 601"), characterized in that each of the secondary temperature sensors (601, 602, 601', 602', 603', 601") of that temperature sensor assembly (400, 400', 400") is positioned close to - the measurement location (901, 902, 903, 901', 902', 903', 901", 902") of one of the primary temperature sensors (501, 502, 503, 501', 502', 503', 501", 502") from a different one of the temperature sensor assemblies (400, 400', 400"), or - a reference location of one of the secondary temperature sensors (601, 602, 601', 602', 603', 601") from a different one of the temperature sensor assemblies (400, 400', 400"). the process vessel comprising at least two process vessel ports (300, 300', 300") at different locations of the process vessel, wherein - at or through each process vessel port (300, 300', 300") a temperature sensor assembly (400, 400', 400") is inserted into the process vessel, - each temperature sensor assembly (400, 400', 400") comprises at least one primary temperature sensor (501, 502, 503, 501', 502', 503', 501", 502"), which is positioned at a measurement location (901, 902, 903, 901', 902', 903', 901", 902") within the process vessel , and - at least one of the temperature sensor assemblies (400, 400', 400") comprises at least one secondary temperature sensor (601, 602, 601', 602', 603', 601"), - at or through each process vessel port (300, 300', 300") a temperature sensor assembly (400, 400', 400") is inserted into the process vessel, - each temperature sensor assembly (400, 400', 400") comprises at least one primary temperature sensor (501, 502, 503, 501', 502', 503', 501", 502"), which is positioned at a measurement location (901, 902, 903, 901', 902', 903', 901", 902") within the process vessel , and - at least one of the temperature sensor assemblies (400, 400', 400") comprises at least one secondary temperature sensor (601, 602, 601', 602', 603', 601"), characterized in that each of the secondary temperature sensors (601, 602, 601', 602', 603', 601") of that temperature sensor assembly (400, 400', 400") is positioned close to - the measurement location (901, 902, 903, 901', 902', 903', 901", 902") of one of the primary temperature sensors (501, 502, 503, 501', 502', 503', 501", 502") from a different one of the temperature sensor assemblies (400, 400', 400"), or - a reference location of one of the secondary temperature sensors (601, 602, 601', 602', 603', 601") from a different one of the temperature sensor assemblies (400, 400', 400"). - the measurement location (901, 902, 903, 901', 902', 903', 901", 902") of one of the primary temperature sensors (501, 502, 503, 501', 502', 503', 501", 502") from a different one of the temperature sensor assemblies (400, 400', 400"), or - a reference location of one of the secondary temperature sensors (601, 602, 601', 602', 603', 601") from a different one of the temperature sensor assemblies (400, 400', 400"). <EOS>