| 摘要 |
<p>The present invention relates to apparatus for determining the liquid level in a non-metallic tank. Measurement means for determining the liquid level in liquid containing tanks are usually positioned within the tank and directly contact the surface of the liquid. Such devices, however, can cause a malfunction of the measuring device and leads to sanitary problems and unpleasant odors. Metal electrodes, probes, or plates can be mounted on the outside of the tank, which plates are insulated from the liquid therein in a manner such that the capacitance between the plates varies as a function of the level of the liquid in the tank. However, after the tank contents will tend to adhere to the walls of the tank, causing an incorrectly high reading. The present invention solves these problems in manner unknown heretofore. With the present measuring means, a pair of parallel plates are secured to the outside of the tank to avoid contact with the liquid inside of the tank. The plates have a generally vertical orientation so that as the liquid rises in the tank, an increasing area of the plates is adjacent to the liquid. The change in capacitance between the plates as a function of liquid level is utilized to generate an electrical signal indicative of liquid level. The problems caused by highly viscous liquids coating the inside surface of the tank and yielding false readings are solved by utilizing a high frequency driving signal.</p> |
