Jeep Repair: jeep oil pressure, electrical signal, pnds

Question
I have a 99 Cherokee 4.0 liter what should the oil pressure be. It has been reading 80 pnds it dropped to 40 I changed the oil its now at 50 pnds

Answer
The MINIMUM oil pump pressure is 89.6 kPa (13 psi) at 600 rpm. The NORMAL oil pump pressure is 517 kPa (75 psi) at 1600 rpm or more.
  the gauge u are looking at is nothing but a dummy gauge and the pressure is false  its a electrical signal to the pcm then u visually see it on the cluster.