Abstract: A strip of resistive carbon is deposited on a longitudinal plastic film and a strip of conductive copper is deposited on a second film. The two film strips are glued together with the resistive and conductive strips opposing to form a sealed envelope having a longitudinal cavity. This sandwich is placed in a flexible extruded tube membrane and the whole inserted in a longitudinal slot in a frame, with a channel communicating with the slot and the exterior of the frame. Liquid in a tank compresses the envelope, causing the copper and carbon strips to contract at a point depending on the level. The change in resistance of the carbon-copper circuit with level produces a changing voltage which is processed to provide a signal indicative of the level of in the tank. Temperature sensors in the frame provide the temperature of the at various levels.

Abstract: A controller including a digital processor is connected to flow meters and overfill gauges suitable for placement in the fill ports of underground storage tanks at, for example, a gasoline service station. The station dispenser pumps are also connected to the controller. In addition, probes, including tank liquid level probes, line pressure probes, and leak probes capable of detecting small quantities of liquid leaking from the system, are also connected to the controller. Processor software programs use stored decision criteria relating liquid conditions external of the storage tank system and liquid conditions internal of the storage tank system and its contents to provide audio and visual indications of the status of the liquid storage system and its contents.

Abstract: A plurality of probes are electrically connected to a central controller. Each of the probes is capable of providing a hydrocarbon signal, a water signal, and a dry signal to the controller upon sensing these respective environments. The controller includes an alarm transducer, relays, a keyboard, and a liquid crystal display (LCD) connected to a microprocessor and associated memories. A software program stored in memory is utilized by the microprocessor to permit users to individually select alarm conditions for each probe and relay and the latching condition for each relay which conditions are stored in memory. The probes that activate each relay may also be selected and stored. There is an RS232 port connected to the microprocessor circuit via which probe status can be requested by and communicated to a remote terminal. Upon receipt of probe signals corresponding to the selected alarm and latching conditions, the microprocessor activates the alarm and relays as programmed.

Abstract: A plurality of probes for sensing their fluid environment are electrically connected to a controller. The controller includes an alarm transducer, relays, a keyboard, and a display connected to a microprocessor and associated memories. Under keyboard control and software direction the microprocessor is operable in a monitor mode in which it monitors the probes and activates the transducer, relays, and display in response to probe signals corresponding to selected alarm conditions, and in a program mode in which the alarm conditions, relay latching conditions, and probe to relay assignments may be selected via the keyboard. A hardware timer interrupts the microprocessor periodically to clock a software timer which provides six second and six minute timers. When monitor mode is exited, the six second timer is reset and if a security code is not entered in six seconds the timer elapses and the system returns to monitor mode.

Abstract: A detector for sensing the presence of polar fluids includes a pair of detection probes and a circuit for providing an oscillating voltage across the probes. A power supply for the detector includes a transformer with a split secondary, with at least one secondary having a floating ground. One of the probes is connected to the floating ground. The other probe is connected to the input of a fluid detection logic circuit. The input is applied to an inverter having an activation threshold of approximately six volts. The resulting activation threshold of the detector circuit is sufficiently low to be activated by the oscillating voltage so as to produce a polar fluid output signal when the probes are immersed in a polar fluid, but sufficiently high so as not to be affected by stray voltages induced in the probes by conventional power lines, such as 120 VAC lines, contacting the polar fluid.