Communications: electrical – Systems – Call station
Patent
1975-03-12
1976-05-11
Queisser, Richard C.
Communications: electrical
Systems
Call station
73304C, 73304R, G01F 2324, G01F 2326, G08B 2100
Patent
active
039567605
ABSTRACT:
A device for indicating the presence or absence of liquid at a single level in a tank, comprising a sealed cylindrical housing having one end wall permanently fixed and the other end wall removable. The housing has an internal shoulder against which the removable wall is seated. The latter has an annular recess extending about its periphery in which there is disposed an O-ring, adapted to sealingly engage the housing wall adjacent the shoulder and thus effect a watertight seal therewith. The removable wall is connected to the fixed end wall by means of draft screws and sealing nuts, the screws having spacers which mount two printed circuit boards in spaced relation with one another inside the housing. The removable end wall also carries at its outer side two concentric, conductor tubes on feed-through insulators, constituting a probe whose conductive or capacitive characteristics vary according to whether the tubes are submerged or dry. The circuitry employed with the probe is disposed inside the housing and includes a signal generator for applying signals to one part of the probe, and amplifier circuitry for receiving signals from another part of the probe. Means are provided for selecting either a.c. or d.c. signals at the output of the generator, enabling the gauge to be used with either dielectric fluids or conductive fluids respectively. The arrangement is such that an especially compact and rugged assemblage is realized, with the supply and signal leads which extend from the housing all being characterized by very low impedance, thus making them highly immune to stray pick-up, hum and the like.
REFERENCES:
patent: 3037165 (1962-05-01), Kerr
patent: 3433072 (1969-03-01), Virtanen et al.
patent: 3475960 (1969-11-01), Miller
patent: 3498131 (1970-03-01), Rickey
patent: 3533286 (1970-10-01), Westcott et al.
patent: 3695108 (1972-10-01), Wygant
patent: 3821900 (1974-07-01), Preikschat
patent: 3831069 (1974-08-01), Merrell et al.
Lehmann H. Gibner
Lehmann K. Gibner
Liquidometer Corporation
Queisser Richard C.
Shoon Frederick
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