What does "internal" and "external" sensor mean?

What does "internal" and "external" sensor mean?

MSR dataloggers are equipped with a temperature, humidity, pressure and acceleration sensor which are "internal" as standard, i.e. they are installed inside the datalogger's case. However, some applications require the use of "external" sensors in order to be able to take readings directly "on-the-spot." For such measurements it is possible to connect the temperature and/or humidity and/or pressure sensor externally with a choice of cable lengths of 15cm, 40cm, 100cm or 160cm. It must be noted here that, for each measurement parameter, either an internal or an external sensor can be connected - but not both internal and external sensors for the same parameter at the same time.