What is Open Area Test Site?

 The Open Area Test Site (OATS) is a flat piece of land, free of obstructions, away from any and all external signals, with a perfectly reflective surface. OATS is used for EMC and emissions testing for large machines. If EMC measurement are done in a room or an enclosed area, it is possible that reflections or scattered signals from walls, floor and ceiling can tamper the readings. Hence, to get repeatable results it is necessary that the testing room should be free from all types of external signals. OATS metallic ground plane and absence of reflecting objects ensure that the measurements will be quite repeatable.

OATS’ construction is quite easy as it does not require much equipment. One of the most important steps is the construction of the metallic surface, which is laid onto the ground to stabilize the grounds reflection co-efficient. The transmitting and receiving antennas used for the measuring the emission of emf from the Equipment Under Test (EUT) must be calibrated precisely. A turntable is also required to get the emf measurements from all the sides of EUT. 

The accurate value of the antenna factor is a fundamental requirement for reliable electromagnetic compatibility (EMC) measurements in emissions, immunity, and interference tests. According to international standards, the equipment is required to be tested in close-to-ideal test sites (or calibration test sites), characterized by very large sizes of the ground plane and of the empty space above it to test the free-space behavior. Testing in the Open Area Test Sites help in achieving these close-to-ideal situations.