The KOBOLD NDT Series static pressure level switch is especially suitable for level monitoring of liquids in open or vented tanks. It uses pressure to measure the height of the liquid above the bottom of its user-supplied sensing tube. Operation of the NDT level switch is simple. Install a pipe on it so that the bottom of the pipe reaches to four inches below the desired switch point. When the liquid level reaches the pipe, it will seal off access to the pipe end.
As the level continues to rise, the static pressure of the liquid will exert a pressure on the air pocket trapped in the pipe (corresponding to the height of the media above the pipe end). The NDT level switch is connected to the air pocket and factory adjusted to trip at 4" of water column pressure. The switching can therefore take place without the moving mechanism ever contacting the media.