Petroleum testing is the analysis during upstream, midstream, and downstream production processes of petroleum products. It is most commonly used to test petroleum product, its product components, byproducts of crude oil, fuel, natural gas, upstream oil and gas and other formats of petroleum. - The instrument is composed of standard color dial, observation lens, light source and color comparing tube. The color dial is rotated by a hand wheel installed at right side of instrument to choose the correct color during color comparing test. The color comparing tube is placed into instrument trough a lid on the top of the instrument. The observation lens is composed of concave mirror and separated bar. You can see two semicircle colors through observation lens. The right semicircle is standard color. The light and focus of optical observation lens can be adjusted, so it is easy to be used.