oil pressure gauge?

[AUcobra94]

My oil pressure gauge is dropping to 0 at low idle, around 800rpm. If it is idling higher than that or if im driving it will go back to normal. Do ya'll think it is the oil pressure sensor or the oil pressure is actually dropping at idle? Has anyone had this happen to them? I'm hoping the motor is gone, I need an excuse to build a new motor.

thanks