A method for determining a salt concentration of a hydrocarbon fluid using a conductivity sensor and a hydrocarbon testing solution includes forming the hydrocarbon testing solution. The light-emitting layer includes a polycrystalline or amorphous material from which light can be trapped by total internal reflection until reaching a region of crystallite size capable of scattering light. The host computer has a list of interface information for different types of flash media cards and references the card type in the list and sets the proper baud rate on the reader. Heated air is removed from each computer system through the vent in the partition that is associated with the computer system.