Abstract: Magnetic flow meters having a streamlined body within a flow tube provide an extended voltage path through a flowing fluid at the expense of flow passage restriction. The voltage path may extend along a circumference of an annular flow region. The use of an extended voltage sensing path increases useful signal levels, which allows for lower cost construction and lower power operation.

Abstract: A flow sensing head for a magnetic flow sensor may be configured as an insertion probe having one or more flow passageways oriented perpendicular to the magnetic axis of an electromagnet. When a conductive liquid flows through the passageway a voltage is induced between two electrodes spaced out along a line perpendicular to the passageway and to the axis of the electromagnet. A portion of the lead wires from the electrodes is fed through an axial throughhole in a conductive core of the electromagnet in order to electrostatically shield the wires from extraneous voltage sources. A preferred flow sensing head has two flow passageways, each with its own pair of electrodes. Signals from the two pairs of electrodes may be combined in a series-aiding arrangement, or in a parallel arrangement, or the signals from the two pairs of electrodes may be processed independently of each other.

Abstract: A transit time ultrasonic flow sensor uses a pair of transducers that alternate between transmitting and receiving operational states, the operating frequency of a reference oscillator driving the transmitting transducer is controllably varied so as to maintain a constant phase relationship between the transmitted and received signals. A second oscillator is slaved, in frequency to the reference oscillator just before the alternation in operational states takes place and retains that frequency for most of the next operational state, and so forth. Fluid flowing along a line between the two transducers causes one of the two oscillators to swing to a higher frequency, and the other to swing low with respect to each other. A difference frequency between the two oscillators is detected and used as a basis for calculating the rate of fluid flow. In preferred versions of the invention the pair of transducers and an acoustic reflector are configured as a probe that can be inserted into the flowing fluid.

Abstract: A magnetic flow sensor using a permanent magnet to provide the magnetic flux is configured to compensate for electrode related drifts. The electrode signals are cyclically short circuited and the flow rate related voltages are isolated from various drift signals during short signal sampling periods. Some versions of the invention use multiple sensing heads in a single sensor to increase the magnitude of the flow related signal.

Abstract: An ultrasonic transit time flow sensor detects a signal corresponding to the phase difference between signals from two transducers during the interval of an acoustic transmission, and uses this signal to adjust an output flow rate signal in order to compensate for circuit errors inherent in the flow sensor. An Exclusive-Or phase detector detects the difference in phase between the signals resulting from the difference in propagation transit time of the flowing fluid. This measured difference includes a phase shift due to the electrical circuits of the flow sensor. In order to compensate for the circuit-induced phase shift, when the transducers are transmitting bursts of acoustic energy, the corresponding electrical signals are routed to the Exclusive-Or phase detector in order to generate a common mode DC signal representative only of the phase shift of the electrical circuits of the flow sensor.

Abstract: A transmitting electro-mechanical transducer is energized by electric pulses at a low frequency (typically several hertz to several kilohertz) to provide corresponding pulses of movement in the fluid. The fluid movement displaces a volume of the fluid in one direction and the motion of that fluid, when combined with the surrounding fluid, produces a fluid rotation which is sustained for a sufficient period of time, to be detected at a later time as an acoustic signal. A known distance downstream of the transmitting transducer, a receiving transducer detects the rotating volume of fluid. From the distance between the transmitting and receiving transducers and the time interval between their transmitted and detected signals, the fluid flow rate can be determined. The transmitting and receiving transducers can interchange their functions so that the difference in the time intervals is used to determine fluid flow rate.

Abstract: A magnetic flow sensor is configured to compensate for electrode related drifts by connecting the electrodes either to each other or to a reference voltage during most of an operating duty cycle. Some versions of the invention use multiple sensing heads in a single sensor to increase the magnitude of the flow related signal, either by interconnecting ones of the electrodes or by externally summing the signals. Additionally, some versions of the sensor can be used with weakly electrically conducting flow conduits, such as blood vessels.

Abstract: A magnetic flow sensor is configured to compensate for electrode related drifts by connecting the electrodes either to each other or to a reference voltage during most of an operating duty cycle. Some versions of the invention use multiple sensing heads in a single sensor to increase the magnitude of the flow related signal, either by interconnecting ones of the electrodes or by externally summing the signals. Additionally, some versions of the sensor can be used with weakly electrically conducting flow conduits, such as blood vessels.

Abstract: A transit time ultrasonic fluid flow sensor is configured to compensate for circuit related drifts in the flow rate output signal. During acoustic transmission some of the transmitting signal is also routed through the receiving circuits from which a reference signal is derived to provide the compensating signal. In an alternate configuration, compensation or flow sensor drift is derived from reception of the round-trip signals between a pair of transducers.

Abstract: An ultrasonic transit time flow sensor employs two transducers spaced out along a direction of fluid flow. A variable frequency acoustic signal is simultaneously transmitted by both transducers in a burst. After an interval corresponding to the expected transit time between transducers, both transducers are switched to their respective receiving states and a phase difference between their received signals is used as a measure of the fluid flow rate. The invention also provides a feedback arrangement for controlling the acoustic frequency to maintain stable operation under a variety of operating conditions.

Abstract: A device for monitoring heat transfer systems. A non-heated temperature sensor is used to determine the approximate temperature of a flowing fluid being monitored. A heated temperature sensor is exposed to and is thereby cooled by the flowing fluid being monitored. A flow measurement is made using a flow sensor and the heat transfer from the heated temperature sensor to the flowing fluid is determined. An electrolytic means is provided for chemically altering the environment of the heat transfer surface of the heated temperature sensor to determine its use or effects for testing, operation and maintenance of the heat transfer system and also the device. A hot tap insertion flow probe configuration is presented which includes a cost effective miniature magnetic flow sensor using permanent magnets.

Abstract: A transit time ultrasonic fluid flow sensor is configured as a self contained modular unit that does not rely on acoustic transmissions through or reflected by a pipe for operation. A highly efficient transducer assembly transmits and receives signals which are well isolated from each other and which enables simplification of the supporting electronics. Continuous wave transmission and reception of the acoustic signals, and provision for acoustic path and electronic drifts enable the sensors to be physically small and yet to exhibit high sensitivity and measurement precision. Some versions of the apparatus sense flow along two orthogonal axes. In addition, electrolytic cleaning is provided for some versions of the sensor.

Abstract: Sensors for measuring the flow rate of fluids flowing through or around a chamber. The chamber is formed using electrically insulating material through which there is an orthogonal alternating magnetic field provided by a mechanically repositioned permanent magnet and at least a pair of electrodes in line with and orthogonal to the magnetic field. This provides an electrical potential with a magnitude proportional to flow rate. The alternating magnetic field may also be provided by a stationary multiple electromagnet. Various embodiments are disclosed which make use of electromagnetics, stepper motors and other modifications for adapting the flow sensor to a wide variety of applications and environmental conditions.

Abstract: A sensor for measuring the flow rate of a fluid through a conduit. The fluid flow rate in the vicinity of a heated temperature sensor is made to cyclically vary from a minimum to a maximum to produce a cyclic signal indicative of the heat removed from the sensor by the fluid flow. The magnitude of the cyclic signal is representative of the mass flow rate of the fluid. A detection circuit responsive to the cyclic signal extrapolates therefrom the mass flow rate and provides an output signal related thereto. Mechanically and electrically balanced configurations enable high speed and high precision measurements to be obtained. Bypass and sampling embodiments are presented. In alternative preferred embodiments circuits are disclosed for determining and maintaining a constant average temperature difference between the sensors and the fluid being sensed, to thereby replace heat loss by the sensors as a result of contact with the fluid being sensed.

Abstract: Sensors for measuring the flow rate of a fluid and for monitoring heat transfer. An induction-heated temperature-responsive sensor in contact with and cooled by the fluid, changes temperature in proportion to the quantity of heat removed by the fluid thereby providing a basis for determining flow rate or heat transfer. A flow modulation method and apparatus for improving the precision of flow rate measurement is also presented.

Abstract: Sensors for measuring the flow rate of fluids flowing through a chamber. The chamber is formed using electrically insulating material through which there is an orthogonal alternating magnetic field provided by a mechanically repositioned permanent magnet and at least a pair of electrodes in line with and orthogonal to the magnetic field. This provides an electrical potential with a magnitude proportional to flow rate. The alternating magnetic field may also be provided by a stationary multiple electromagnet. Various embodiments are disclosed which make use of electromagnetics, stepper motors and other modifications for adapting the flow sensor to a wide variety of applications and environmental conditions.

Abstract: An electro-mechanical, dual tube and plug device for on-line monitoring of performance losses due to reduced conductivity of a heat exchanger resulting from micro-bio fouling of the surfaces of said heat exchanger/condenser and for detecting change of heat transfer resistance of individual heat transfer tubes. The dual tube and plug assembly includes a first flow assembly tube and a second temperature assembly tube attached to the discharge end of a heat exchanger for providing accurate measurement of temperature and cooling water flow. The first flow assembly tube includes a tube having an inner chamber, including a flow sensor comprising a paddle wheel and a sensor and a temperature sensor for measuring discharge water temperature. The second temperature assembly tube plugs the inlet and the outlet of a heat transfer tube immediately adjacent to the flow assembly tube and includes a plurality of spring loaded temperature sensors in the plugged empty heat transfer tube.

Abstract: Apparatus is provided in which flow to be monitored actuates a device to move past a sensing electrode, causing changes of a capacitive sensing impedance in series with an impedance transformation device. The sensing electrode is at the high-impedance level of the impedance transformation device. Only a small fraction of the stray capacitance of circuit wiring, etc., which is connected at the low-impedance level of the impedance transformation device is reflected as a dulling shunt across the sensing capacitance.

Abstract: A flow meter for measuring extremely low flow rates of fluids by cyclically controlling the flow from a maximum to a minimum condition in the vicinity of a thermistor. The magnitude of the modulation component of the electric signal is representative of flow rate. In an alternate embodiment, the thermistor is cyclically moved in the flow stream to establish the modulation or the movement simulated by pumped flow past the thermistor.

Abstract: Temperaature sensors at the inlet and outlet of a heat exchanger are utilized in the disclosed apparatus to measure the temperature of the fluid and to ascertain the the time taken by a localized gradient in heated or cooled fluid to pass through the heat exchanger at the start of a heating or cooling episode in order to obtain the flow rate of fluid through the heat exchanger; a representation of the flow rate is stored; and thereafter, during that heating or cooling episode, the stored flow-rate representation is utilized in deriving flow-rate and energy transfer measurements.