Testo Data Logger. Testo offers a large range of data loggers for long-term recording of measurement data, e.g. for climate or temperature monitoring. The use of a data monitoring system is recommended for integrated measurement data monitoring. The testo Saveris system offers tamper-proof data recording. The testo Saveris 2’s WLAN technology means your measurement data is available to you anywhere and at any time (on the PC, smartphone or tablet).