Question: 

How do I lock or unlock the screen of my 173x logger ? 

Answer: 

The 173x series Energy logger has the option to lock the screen to prevent unwanted key-pressing. 
This option is only available during an active logging. 

A grey button in the screen with Lock Screen will lock it after putting in the default Pin-code which is 1234.
See the video below how to lock and unlock your screen: