Industrial enterprises producing deep-fried snack foods such as potato chips or pre-fried French fried potatoes use automated frying systems that consist mainly of the actual frying pan, a tube type heat exchanger to heat the frying oil, a filter, a circulation pump, a banana tank for fresh oil and the automation system, most often a PLC.[citation needed] As the product leaving the fryer contains a percentage of oil (in potato chips approx. 35%)[citation needed] there is a constant flow of fresh oil into the system. Sensors for the temperature of the oil, the oil level, different pressures in the system and other parameters are used as input for the PLC.[