Abstract: A method and apparatus for pre-calibrating capacitive-type fuel quantity probes is proposed in which a voltage divider excitation source is connected to the low impedence electrode of the probe and is used to trim the apparent capacitance down to within a small tolerance of .+-.0.1% of the precise design value for the probe.

Abstract: An electrode assembly for use in a capacitance type probe for measuring volume or height of an electrically conductive liquid. The probe includes an inner conductor which an electrical conductive wire is connected at one end. The inner conductor is surrounded by a thick-wall TEFLON tube which functions as an insulator. A thin-wall TEFLON sleeve is heat shrunk onto the thick-wall TEFLON tube and the ends of the thin-wall sleeve are heated and sealed about the thick-wall tube to prevent any leakage of fluid to the inner conductor. The assembly is also provided with a polyurethane foam to provide rigidity and to prevent moisture from forming within the assembly.

Abstract: A signal selection system, including a plurality of detection circuits having inputs receiving respective direct voltage signals and outputs connected to a scan bus. Each detector circuit includes an operational amplifier having a non-inverting input receiving one of the direct voltage signals, an inverting input connected to the scan bus, and an output connected via a diode to the scan bus, so that the scan bus is maintained at essentially the highest or lowest signal of the signals being scanned, depending on the orientation of the detector circuit diodes. The system includes a plurality of indicators, associated respectively with the detector circuit diodes, for indicating whenever the associated diode is forward-biased, and an alarm circuit connected to the scan bus for indicating whenever the scan bus voltage exceeds a maximum value if the signal being detected is the highest signal, or whenever the scan bus voltage is less than a minimum value if the signal being detected is the lowest signal.

Abstract: A signal transmission system responsive to A.C. signals has rectifier means arranged to receive the A.C. signals. The rectifier means are connected to first and second circuit paths so as to establish respective unidirectional currents of opposite polarity and dependent on the A.C. signals, in the two circuit paths. Integrating means are connected to at least one of the circuit paths to integrate the current therein to thereby produce an output signal dependent on the A.C. signal but independent of any stray A.C. pickup on either circuit path.