When the AC Adapter is plugged into the wall and balance, then the balance is powered ON, or the manufacturer calls this "Standby" mode. When you press the On/Off keypad this is turning on the display. So if you Entris64 was not plugged in then the warm up time is 30 minutes. If your balance was always plugged in and you are just pressing the On/Off keypad to turn on the display then there is no warm up time since the Entris was always powered. If you have more questions please call us at 978-521-7095. Precision Weighing Balances is an Authorized Stock Dealer and we really know lab balances. To purchase a Sartorius Balance visit either www.balances.com or www.scaleman.com