Connecting a kitchen weighing scale to an AC/DC adapter
Is the voltage stable? if it has spikes over 3.5V, it may damage the scale, meant to be used with very stable and spike-free 3.3 V cells. Many AC/DC adaptors have significant spikes when used with very light loads (and the scale is a VERY light load).

Also, why do you do that? a wall socket is quite valuable in the kitchen, and a CR2032 cell should last months on a kitchen scale anyway. It's not a shaver which needs significant power...

Moreover, the AC/DC adapter will draw continuously some power even when the scale is off. You lose a wall socket and you waste energy!