Abstract: A system for point-level detection of material within a vessel includes a transmission line probe adapted to be mounted to a wall of the vessel so as to extend within the vessel for contact with material when the material reaches a preselected level within the vessel. Electronics are operatively coupled to one end of the probe for launching microwave energy along the probe. The electronics are responsive to a change in microwave energy reflected from the free end of the probe within the vessel when the material is in contact with the probe, employing time-domain reflectometry techniques, for indicating that the material is in contact with the probe. This change in reflected microwave energy may comprise a change in phase or, more preferably, a change in apparent length of the probe resulting from contact with material having a higher dielectric constant than that of air when air surrounds the probe.

Abstract: Apparatus for measuring concentration of solid particles in a fluid stream that includes a probe for disposition in the fluid stream to provide an electrical probe signal as a triboelectric function of concentration of solid particles in the fluid stream. A first circuit is coupled to the probe for providing a first electrical signal as a proportional function of the probe signal. A second circuit is coupled to the probe for providing a second electrical signal as a function of rate of change of the probe signal. Differential amplifiers received the first and second signals, and provide a third signal as a function of a difference therebetween. An apparatus output signal is provided when such difference exceeds a preselected threshold.

Abstract: A photo-optical coupler is connected to a shaft to provide a series of electronic pulses at a frequency corresponding to rotational velocity of the shaft. Apparatus electronics is responsive to frequency of such pulses for indicating a low speed alarm condition when such frequency is below a preselected threshold. The apparatus electronics includes a digital counter that is set to a first preselected count upon occurrence of each of the shaft rotation pulses, and which is thereafter decremented between the shaft rotation pulses. A low speed alarm condition is indicated if the counter reaches a count of zero prior to a succeeding shaft rotation pulse. In the preferred embodiment, the counter is decremented by an oscillator having a clock frequency coordinated with the first preselected count so as to activate the alarm when rotational velocity of the shaft decreases to a predetermined threshold percentage of a nominal rotational velocity of the shaft.

Abstract: A system for indicating level of material in a vessel as a function of material capacitance includes a capacitance probe adapted to be positioned so as to be responsive to variations in capacitance as a function of material level in the vessel. Detection circuitry is responsive to capacitance at the probe and to a reference signal for indicating material level, and includes facility for selectively adjusting sensitivity of the detection circuitry to material capacitance so as to adapt the system for materials of differing capacitance characteristics. Calibration circuitry for establishing the reference signal includes facility for varying operating characteristics of the detection circuitry during a calibration mode of operation independent of material level so as to calibrate the detection circuitry to capacitance at the probe.