The OilArm uses a much-tested electro-optical sensing system to measure the concentration of oil in water. A 3ml sample is drawn by a piston into a small glass chamber. A tiny light source shines through one wall of the chamber to two photodetectors on the other side. Any oil suspended in the sample absorbs light. The decrease in light transmission is measured by one photodetector, and the forward scattered light preferentially induced by oil is measured by the other photodetector, which is shielded from directly viewing the light source by an occluding rod. An electronic circuit algebraically combines the intensity on the two photodetectors to yield a measure of the concentration of oil. The dual approach minimizes interference from suspended solids or air bubbles. Water temperature and oil composition do not affect the reading.
Installation is easy and inexpensive. The sampling end of the sensor is inserted 6 to 12 mm into the stream to be sampled. The sensor is held in place by a 150lb Navy or optional ANSI 4-hole flange.