Abstract: An electromagnetic flowmeter comprising a body having a central channel having a measuring region, an inlet region and an outlet region. Relative to liquid flow through the central channel, the inlet region is upstream of the measuring region, and the outlet region is downstream of the measuring region. The inlet region and outlet region have diameters substantially greater than the diameter of the measuring region. A transition region extends between the inlet region and the measuring region, and a transition region extends between the measuring region and the outlet region. First and second cavities are respectively positioned in the inlet region and the outlet region, and third and fourth diametrically opposed cavities extend from the measuring region of the central channel. First and second grounding electrodes are respectively positioned in the first and second cavities, and third and fourth measuring electrodes are respectively positioned in the third and fourth cavities.

Abstract: A probe developing an admittance with a material whose condition is to be continuously measured is capacitively coupled with a variable frequency oscillator, preferably one having a digital output stage, for generating a variable frequency signal having a period varying with the admittance developed at the probe. Both the oscillator input and output are capacitively coupled to the probe. In a preferred embodiment, a set point circuit including a plurality of resistors coupled in parallel with the oscillator output and a plurality of switches coupled in parallel with the probe conductor and each with a different one of the resistor, provides easy circuit adjustment for use of the system with a variety of materials. A preferred digital circuit employing a pair of flip flops, fixed timer and one shot generate a fixed period variable duration duty cycle digital voltage level signal for transmission, if desired, or for conversion into a variable current signal.

Abstract: A probe developing an admittance with a material whose condition is to be continuously measured is capacitively coupled with a variable frequency oscillator, preferably one having a digital output stage, for generating a variable frequency signal having a period varying with the admittance developed at the probe. Both the oscillator input and output are capacitively coupled to the probe. In a preferred embodiment, a set point circuit including a plurality of resistors coupled in parallel with the oscillator output and a plurality of switches coupled in parallel with the probe conductor and each with a different one of the resistor, provides easy circuit adjustment for use of the system with a variety of materials. A preferred digital circuit employing a pair of flip flops, fixed timer and one shot generate a fixed period variable duration duty cycle digital voltage level signal for transmission, if desired, or for conversion into a variable current signal.

Abstract: A probe developing an admittance with a material whose condition is to be continuously measured is capacitively coupled with a variable frequency oscillator, preferably one having a digital output stage, for generating a variable frequency signal having a period varying with the admittance developed at the probe. Both the oscillator input and output are capacitively coupled to the probe. In a preferred embodiment, a set point circuit including a plurality of resistors coupled in parallel with the oscillator output and a plurality of switches coupled in parallel with the probe conductor and each with a different one of the resistor, provides easy circuit adjustment for use of the system with a variety of materials. A preferred digital circuit employing a pair of flip flops, fixed timer and one shot generate a fixed period variable duration duty cycle digital voltage level signal for transmission, if desired, or for conversion into a variable current signal.

Abstract: A probe developing an admittance with a material whose condition is to be continuously measured is capacitively coupled with a variable frequency oscillator, preferably one having a digital output stage, for generating a variable frequency signal having a period varying with the admittance developed at the probe. Both the oscillator input and output are capacitively coupled to the probe. In a preferred embodiment, a set point circuit including a plurality of resistors coupled in parallel with the oscillator output and a plurality of switches coupled in parallel with the probe conductor and each with a different one of the resistor, provides easy circuit adjustment for use of the system with a variety of materials. A preferred digital circuit employing a pair of flip flops, fixed timer and one shot generate a fixed period variable duration duty cycle digital voltage level signal for transmission, if desired, or for conversion into a variable current signal.

Abstract: An electromagnetic flowmeter in which the fluid being metered passes through a flow tube to intersect the lines of flux of a magnetic field produced by an electromagnet whereby the resultant voltage induced in the fluid is transferred to a pair of electrodes mounted at diametrically-opposed positions on the tube. The electromagnet is so driven as to produce a flux field having a triangular wave form. The voltage signal yielded by the electrodes is therefore a composite having a triangular wave component that is a replica of the flux wave and a rectangular wave component that is generated by a spurious loop pick up voltage. The composite signal is applied to a converter and processed therein to cancel out the rectangular wave component whereby the converter output signal is accurately proportional to the flow rate of the fluid.

Abstract: A system operating in conjunction with a computer whose central processing unit is adapted to process data fed thereto by a variable data source to yield at its output port, parallel binary-coded data having an even number of bits which are supplied to a data bus. The system is coupled to the data bus and includes a series of binary rate multipliers to convert the binary-coded data to a conversion frequency which is divided to provide an output frequency in a range suitable for indicating the variable data and which is at the same time converted to an output current proportional to the variable data. The output frequency and output current are electrically isolated from the computer and its associated data source to avoid any interaction therewith.

Abstract: An electromagnetic flowmeter system in which the flow rate signal yielded by the flowmeter primary is applied as an input to a secondary which acts to measure the ratio of the input signal to a reference voltage proportional to the magnetic flux established in the primary, the reference voltage reflecting variations in this flux. Ratio measurement is effected in the secondary by means of a feedback loop in which the reference voltage is pulse-modulated by pulses having a constant width and a frequency which varies in accordance with the flow rate, the pulses having a duty cycle sufficient to cancel the input signal at the input of a summing amplifier. When the variable frequency pulse output from the secondary accurately represents the flow rate, the pulse-modulated reference voltage will then be equal in magnitude and opposite in phase to the input signal.

Abstract: An electronic totalizer having a non-destructive readout indicative of the time-integrated total of a process variable such as flow rate, metered by a transducer whose output signal lies within a predetermined current range. In the totalizer, the transducer signal is converted into a proportional voltage signal that is applied to a voltage-to-frequency converter yielding pulses at a rate which varies with the magnitude of the voltage signal, the pulse frequency being high at the upper limit of the range. The converter pulses are fed to an adjustable scaler yielding output pulses at a scaled-down rate appropriate to the desired unit of measurement, these being applied to a counter which gives a totalized reading. By setting the scaler, one may establish a reading in useful increments of process flow, such as gallons or liters.

Abstract: An analog-to-digital converter for an electromagnetic flowmeter in which the fluid being metered passes through a flow tube to intersect a magnetic field, the voltage induced in the fluid being transferred to a pair of electrodes. The magnetic field is established by an electromagnet supplied with excitation current that is alternately turned "on" and "off" at a low frequency rate. The resultant flow-induced electrode signal is sampled for a predetermined interval in each "on" and "off" field state, successive differences therebetween serving to develop an analog signal representing the flow rate. Conversion is effected by integrating each sample to produce a sloped voltage whose polarity corresponds to that of the sample and whose peak level relative to a base level is determined by the amplitude of the sample, the sloped voltage being then de-integrated back to base level in a time slot whose duration is directly proportional to the average level of the sample.

Abstract: An electromagnetic flowmeter capable of accurately measuring the flow rate of fluid conveyed on a line in either direction. The flowmeter includes a primary whose flow tube is provided with electrodes yielding a signal depending on the flow rate of the fluid intersecting a magnetic field established in the tube, the sense of the signal changing with the direction of flow. This electrode signal is applied to a secondary in which the electrode signal is converted by demodulator means into a d-c signal whose magnitude is a function of flow rate and whose polarity depends on the sense of the electrode signal. This d-c signal is converted into variable-frequency pulses which exhibit a duty cycle proportional thereto, the pulses being sampled and fed back through a feedback loop to one input of a summing junction to which the electrode signal is also applied as another input, the ouptut of the junction being fed to the demodulator means.

Abstract: An electronic totalizer interposable in the line of a two-wire transmitter having a transducer which converts a metered variable into a current signal that is conveyed over the line to a receiving station, the same line delivering direct current power from the station to the transducer and to the totalizer. The totalizer input circuit includes a resistor through which the current signal flows to produce a corresponding voltage signal, the voltage signal being applied to a resettable integrator to produce a time-integrated voltage which rises above a base level at a rate depending on the varying magnitude of the voltage. The rising integrated voltage is applied to a comparator having a threshold set by a reference voltage to produce an output signal when the integrated voltage reaches the threshold. The output signal is fed back to the integrator to effect resetting thereof to the base level, the output signal also serving to trigger a one shot generating a pulse which is applied to a digital counter.