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Title: Capacitance-level/density monitor for fluidized-bed combustor

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 characteristicsmore » (slower sampling rate).« less

Inventors:
 [1];  [1]
  1. (Morgantown, WV)
Issue Date:
Research Org.:
National Energy Technology Laboratory, Pittsburgh, PA, and Morgantown, WV
OSTI Identifier:
864340
Patent Number(s):
4350040
Assignee:
United States of America as represented by United States (Washington, DC) NETL
Resource Type:
Patent
Country of Publication:
United States
Language:
English
Subject:
capacitance-level; density; monitor; fluidized-bed; combustor; multiple; segment; three-terminal; type; capacitance; probe; selection; detection; compensation; circuitry; read-out; control; level; measurements; vessel; provided; driven; excitation; frequency; 50; khz; sense; quadrature; capacitive; current; related; relatively; insensitive; resistance; component; generating; negative; equal; magnitude; cancel; resistive; clock-operated; separately; selects; segments; predetermined; detecting; storing; measurement; selected; guarded; electrode; connected; unselected; form; guard; signal; directed; corresponding; channel; sample; hold; circuit; dedicated; store; derived; provides; parallel; outputs; display; computer; input; etc; detected; values; rate; sampling; varied; dynamic; profile; bed; average; characteristics; slower; density profile; control circuitry; negative current; excitation frequency; guard electrode; density measurement; control circuit; bed combustor; hold circuit; signal derived; resistive component; capacitance probe; parallel output; relatively insensitive; sampling rate; fluidized-bed combustor; density monitor; selected probe; equal magnitude; compensation circuit; /73/324/

Citation Formats

Fasching, George E., and Utt, Carroll E. Capacitance-level/density monitor for fluidized-bed combustor. United States: N. p., 1982. Web.
Fasching, George E., & Utt, Carroll E. Capacitance-level/density monitor for fluidized-bed combustor. United States.
Fasching, George E., and Utt, Carroll E. Fri . "Capacitance-level/density monitor for fluidized-bed combustor". United States. https://www.osti.gov/servlets/purl/864340.
@article{osti_864340,
title = {Capacitance-level/density monitor for fluidized-bed combustor},
author = {Fasching, George E. and Utt, Carroll E.},
abstractNote = {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).},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {1982},
month = {1}
}

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