2001 Vauxhall Astra Oil Light

The oil light came on yesterday, i checked the oil and it was a little low, so i topped it up to the correct level, now when the engine get to running temp, and i brake the light comes on, when i accelerate away the light goes off, i have checked the oil a couple of times since and the level is the perfect, please can you advise me if its just a electrical fault or is it more engine mechanical.

Thanks