oil light keeps comming on

My oil light goes on and off. I had the oil changed and I check the levels. I am worried about pressure problems, but it feels like it is running fine. It's a 1990 with about 120,000 miles on it. I hope it's just a bad censor, but our battery light did the on and off thing and it turned out our new alternator needed replaced. Any advice would be appreciated. I don't want to do more harm to the car by ignoring the problem.

I have a 96 with 86K mi and the oil light comes on frequently even though I know that the pressure and level is good because I checked. I suspect a dirty or bad sensor. I further suggest that you install a gauge in place of the idiot light. Otherwise, check the level frequently and try cleaning, or better, replacing the sensor.