+ add description for operation with power supply

software/README.md

@@ -135,6 +135,18 @@ then the expiration time of individual sensor data in home assistant.
 
 
 
+Power supply operation
+----------------------
+
+You should remove the battery
+if you want to operate the sensor with a power supply constantly connected.
+This is because measurements will be influenced by the heat generated by the charging circuit.
+
+In addition the temperature measurement may differ because of different voltage levels given to the sensor.
+Therefore you may need to adapt the temperature offset/calibration mentioned below in the "Known issues" section.
+
+
+
 Calibration
 -----------