Measuring and testing – Liquid level or depth gauge – Immersible electrode type
Patent
1980-06-26
1982-09-21
Yasich, Daniel M.
Measuring and testing
Liquid level or depth gauge
Immersible electrode type
324 61P, G01F 2326, G01R 2726
Patent
active
043500404
ABSTRACT:
A multiple segment three-terminal type capacitance probe with segment selection, capacitance detection and compensation circuitry and read-out control for level/density measurements in a fluidized-bed vessel is provided. The probe is driven at a high excitation frequency of up to 50 kHz to sense quadrature (capacitive) current related to probe/vessel capacitance while being relatively insensitive to the resistance current component. Compensation circuitry is provided for generating a negative current of equal magnitude to cancel out only the resistive component current. Clock-operated control circuitry separately selects the probe segments in a predetermined order for detecting and storing this capacitance measurement. The selected segment acts as a guarded electrode and is connected to the read-out circuitry while all unselected segments are connected to the probe body, which together form the probe guard electrode. The selected probe segment capacitance component signal is directed to a corresponding segment channel sample and hold circuit dedicated to that segment to store the signal derived from that segment. This provides parallel outputs for display, computer input, etc., for the detected capacitance values. The rate of segment sampling may be varied to either monitor the dynamic density profile of the bed (high sampling rate) or monitor average bed characteristics (slower sampling rate).
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Fasching George E.
Utt Carroll E.
Besha Richard G.
Breeden David E.
Hamel Stephen D.
The United States of America as represented by The United States
Yasich Daniel M.
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