Abstract: A sensor and alarm device for sensing the level of a liquid in a non-conductive container, the device including a condenser plate assembly to be secured to the container for capacitive coupling to its liquid contents and further including an electronic capacitive bridge circuit connectable to said condenser plate assembly and operative to actuate an alarm circuit when the sensed level is reached by the liquid, the condenser plate assembly comprising a flexible web having adhesive on one side and having electrically conductive flexible condenser plates fixed to the other side of said web, said web and said condenser plates being folded along plural transverse lines so that one portion of the web and the plates overlap with another adjacent portion thereof to form a connector tab, and the device including a housing for containing said capacitive bridge circuit, the housing supporting multiple electrical contacts operative to mate with and grip said tab and secure the housing thereon, and the contacts providing

Abstract: This invention relates to a device for detecting a fall of level of flowable material in a closed container by emitting an oscillation. It is electronic in nature and the circuit has an amplifier with a feed-back terminal that is connected to a feed-back network. The feed-back network in turn includes two vertically spaced apart identical probe condensers each having an open dielectric space and each being in different feed-back paths of the feed-back network. The feed-back network is activated as the level of the flowable material drops, whereby the difference in the dielectric material of the condensers provides a change in input current to the amplifier. The circuit is responsive to a positive change in input current to cause the amplifier to commence oscillation on dropping of the level past the condensers to signal the drop of the level of the flowable material. The device is stable in design, low in cost and easy and reliable to use.