If Power Off is active, then in the case the measurement is in progress, any
attempt to switch off the instrument will be warned "Measurement in progress".
You should stop the measurement to be able to turn off the unit. When the
measurement is completed the warning "Power Off" becomes active. Then, if you
would like to turn off the instrument, you should confirm this.
If Preampl. is active, there will be warning if the instrument detects that there is
no preamplifier attached to the instrument’s input.
If Changes is active, the instrument displays the warning message in the case
when some parameters were changed, but the list of parameters was exit with
the <ESC> key.