An apparatus for and a method of adjusting a primary color component of an image and a computer-readable recording medium for storing a computer program for controlling the apparatus. According to one method, an authorization to access programming mode signal is received at the fuel dispenser from an authorization terminal coupled to the fuel dispenser. Pre-heat coils are located between the sample switching system and the sample shut off system to warm the gas sample and to act as a flow restrictor. A map of at least the region of the sample is created, indicating the specimen current measured in response to the irradiation at the plurality of the locations.