Compact light instruments, are ideal for measurement and record of signals, they are intended for the measurement and the writing into the memory of the values of the temperature before different time intervals with the use of the built-in or external sensor. 3632-20 this is the registrar, that has the watertight construction with the built-in sensor. 3633-20 this the registrar, that has the built-in sensor or is possible the connection of external sensor (option). Large volume of internal storage, to 16000 elements of data.