Most engines use a pressure switch to detect oil level, if there is pressure in the galleys that the oil is pumped into ,there is oil..As you mentioned the oil is splashed around in the crankcase while the engine is running and determining the oil level would be difficult. One alternitave would be to check oil temperature, when an engine is low on oil the oil will run hotter than usual.. You haven't mentioned the type of engine, so we don't know if we're dealing with a lawnmower or a oceanliner...