液位傳感第2部分：光學、重力和聲波技術

　　在上一篇關于液位傳感的文章中，我們討論了可以通過機電開關、霍爾效應開關、電阻分壓器傳感和基于電容定時的傳感技術和方法來檢測液位和限制的技術和產品。

　　本文探討通過光學，重力和聲波技術的液位檢測。

　　分離步驟檢測

　　雖然電阻和電容技術是有效的，易于實現，但它們不是檢測揮發性和有毒液體的最佳選擇。在這里，你想消除任何暴露在電，甚至潛在的電弧，可以爆炸點燃液體。

　　與第1部分中描述的離散步驟傳感器技術類似，隔離步驟檢測，而不是使用單獨安裝的機電開關，使用在所需光波長上為透明或半透明的單個垂直柱。

　　Several optical-slot-type sensors can be employed. For industrial designers， well- engineered off-the-shelf solutions such as the Omron EE-SPX613 should be considered. This is a sealed and self-contained optical slot sensor that can use 6 to 13-mm tube diameters with a wall thickness up to 1 mm.

　　These 12 to 24-V parts are more than just emitters and detectors. They contain a bit of intelligence. The sensitivity is adjustable， and there is a mode select option as well. There is also a built-in amplifier with an open collector 100-mA npn transistor output capable of driving a load relay directly （Figure 1）.