System comprising: a field device for measuring and/or monitoring at least one measured variable, an additional module for the field device and a modular construction kit comprising various measuring modules, wherein the field device comprises a measuring device for metrological detection of the measured variable and a process connection, wherein the process connection is designed to fasten the field device to a place of use in such a way that an area of the field device facing the process and comprising at least a part of the measuring device is exposed to prevailing process conditions at the place of use and an area of the field device facing away from the process is exposed to prevailing ambient conditions at the place of use, wherein the additional module comprises fastening means by means of which the additional module can be mounted or is mounted on the area of the field device remote from the process, wherein the additional module comprises at least one receiving device which is designed as a slot and into which a measuring module selectable from the measuring modules of the modular construction kit can be inserted or inserted in such a way that at least one outer side of the respective measuring module is exposed to the ambient conditions, wherein each measuring module is designed to measure at least one environmental parameter and/or at least one effect of the environmental conditions on the respective measuring module, and wherein the additional module comprises an evaluation unit which is designed to determine an instantaneous load acting on the field device equipped with the additional module and/or a total load to which the field device equipped with the additional module has been exposed in total during its period of use to date on the basis of the environmental parameters and/or effects recorded by means of the selected measuring modules inserted in the receiving devices and connected to the evaluation unit. wherein the field device comprises a measuring device for metrological detection of the measured variable and a process connection, wherein the process connection is designed to fasten the field device to a place of use in such a way that an area of the field device facing the process and comprising at least a part of the measuring device is exposed to prevailing process conditions at the place of use and an area of the field device facing away from the process is exposed to prevailing ambient conditions at the place of use, wherein the additional module comprises fastening means by means of which the additional module can be mounted or is mounted on the area of the field device remote from the process, wherein the additional module comprises at least one receiving device which is designed as a slot and into which a measuring module selectable from the measuring modules of the modular construction kit can be inserted or inserted in such a way that at least one outer side of the respective measuring module is exposed to the ambient conditions, wherein each measuring module is designed to measure at least one environmental parameter and/or at least one effect of the environmental conditions on the respective measuring module, and wherein the additional module comprises an evaluation unit which is designed to determine an instantaneous load acting on the field device equipped with the additional module and/or a total load to which the field device equipped with the additional module has been exposed in total during its period of use to date on the basis of the environmental parameters and/or effects recorded by means of the selected measuring modules inserted in the receiving devices and connected to the evaluation unit.