# US 8,783,088 B2 · Apparatus and method for determining displacer position in a flowmeter prover > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,783,088 B2 - Document ID: US8783088B2 - Status: Granted - Kind: B2 - Application number: 13/278,416 - Filed: 2011-10-21 - Published: 2012-07-26 - Granted: 2014-07-22 - Earliest claimed: 2011-01-21 - Assignees: Daniel Measurement and Control, Inc. - Applicants: Drew S. Weaver - Inventors: Drew S. Weaver - Web page: https://patentgrep.com/patent/US8783088B2 ## CPC - G01F 25/11: {using a seal ball or piston in a test loop} - G01F: MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME ## Abstract Apparatus and methods for proving a flowmeter. In one embodiment, a flowmeter prover includes a flow tube, a displacer, and a signal analyzer. The displacer is moveable in a flow passage of the flow tube. A magnetic target is disposed on the displacer. One or more inductive transducers are disposed on the flow tube and configured to detect the magnetic target as the displacer moves in the flow tube. The signal analyzer is configured to detect a maximum slope of rising and falling edges of a signal generated by the transducer responsive to the magnetic target traversing the transducer. The signal analyzer is further configured to determine displacer velocity based on the detected maximum slope. ## Claims ### Claim 1 A flowmeter prover, comprising: a flow tube; a displacer moveable in a flow passage of the flow tube; a magnetic target disposed on the displacer; at least two inductive transducers disposed on the flow tube, the transducers configured to detect the magnetic target as the displacer moves in the flow tube; and a signal analyzer configured to: detect a signal indicative of change of inductance of each transducer caused by the magnetic target moving across the transducer; and determine displacer velocity based on edges of the signal. ### Claim 2 (depends on 1) The flowmeter prover of claim 1, further comprising a signal conditioning circuit coupled to each transducer, the signal conditioning circuitry configured to generate, for each transducer, a signal comprising a pulse having a slope corresponding to the rate of change of inductance of the transducer. ### Claim 3 (depends on 2) The flowmeter prover of claim 2, wherein the signal analyzer is configured to determine a position of the displacer in the flow tube based on a point of maximum slope of the pulse. ### Claim 4 (depends on 2) The flowmeter prover of claim 2, wherein the signal analyzer is configured to identify a first detection point as a point of maximum slope of a rising edge of the pulse and a second detection point a point of maximum slope of a falling edge of the pulse. ### Claim 5 (depends on 4) The flowmeter prover of claim 4, wherein the signal analyzer is configured to determine the velocity of the displacer based on the first detection point and the second detection point. ### Claim 6 (depends on 4) The flowmeter prover of claim 4, wherein the signal analyzer is configured to determine whether the velocity of the displacer is uniform over the length of the flow tube based on determined velocity of the displacer as the displacer moves across each transducer. ### Claim 7 (depends on 4) The flowmeter prover of claim 4, wherein the signal analyzer is configured to verify performance of the flowmeter prover by comparing the time between the first detection point and the second detection point to previously recorded times between the first detection point and the second detection point at a given displacer velocity. ### Claim 8 (depends on 4) The flowmeter prover of claim 4, wherein the signal analyzer is configured to verify performance of the flowmeter prover by verifying a plurality of volumes defined by one of the first and second detection points of one of the transducers and one of the first and second detection points of one of another of the transducers. ### Claim 9 (depends on 4) The flowmeter prover of claim 4, wherein the signal analyzer is configured to determine a travel direction of the displacer in the flow tube based on the first detection point and the second detection point. ### Claim 10 (depends on 2) The flowmeter prover of claim 2, wherein the signal analyzer is configured to verify performance of the flowmeter prover by comparing the signal generated by the signal conditioning circuit for each transducer at a given flow rate to stored baseline signals for each transducer at the given flow rate. ### Claim 11 (depends on 1) The flowmeter prover of claim 1, wherein the flow tube and the displacer comprise at least one of a non-magnetic material and a paramagnetic material. ### Claim 12 (depends on 1) The flowmeter prover of claim 1, wherein the transducer and signal analyzer are configured to measure displacer velocity of a bidirectional fluid flow at a fluid temperature of −380 degrees Fahrenheit to 800 degrees Fahrenheit. ### Claim 13 (depends on 1) The flowmeter prover of claim 1, wherein the signal analyzer configured to: detect a rate of change of inductance of each transducer caused by the magnetic target moving across the transducer; and determine displacer velocity based on a maximum of the detected rate of change of inductance. ### Claim 14 A method for proving a flowmeter, comprising: inducing movement of a displacer in a flow tube of a prover by fluid flow; changing inductance of an inductive transducer coupled to the flow tube based on proximity of a magnet target of the displacer to the transducer; detecting a signal indicative of change of the inductance; and determining displacer velocity based on edges of the signal. ### Claim 15 (depends on 14) The method of claim 14, further comprising generating a signal based on the output of the transducer, the signal comprising a pulse having a slope corresponding to the rate of change of inductance of the inductive transducer. ### Claim 16 (depends on 15) The method of claim 15, further comprising verifying performance of the prover by comparing the signal generated based on the output of the transducer at a given flow rate to stored baseline signals for the transducer at the given flow rate. ### Claim 17 (depends on 15) The method of claim 15, further comprising determining a position of the displacer in the flow tube based on a point of maximum slope of the pulse. ### Claim 18 (depends on 17) The method of claim 17, further comprising: identifying a first detection point as a point of maximum slope of a rising edge of the pulse; and identifying a second detection point a point of maximum slope of a falling edge of the pulse. ### Claim 19 (depends on 18) The method of claim 18, wherein determining displacer velocity comprises determining the time interval defined by the first and second detection points and the distance traveled by the displacer in the time interval. ### Claim 20 (depends on 18) The method of claim 18, further comprising determining whether the velocity of the displacer is uniform over the length of the flow tube based on a comparison of displacer velocity at each of a plurality of inductive transducers, the velocity derived from the first and second detection points associated with the transducer. ### Claim 21 (depends on 18) The method of claim 18, further comprising verifying performance of the prover by comparing the time between the first detection point and the second detection point to previously recorded times between the first detection point and the second detection point at a given displacer velocity. ### Claim 22 (depends on 18) The method of claim 18, further comprising verifying performance of the prover by verifying a plurality of volumes defined by one of the first and second detection points of one of a plurality of inductive transducers and one of the first and second detection points of one of another of the plurality of transducers. ### Claim 23 (depends on 18) The method of claim 18, further comprising determining a travel direction of the displacer in the flow tube based on the first detection point and the second detection point. ### Claim 24 (depends on 14) The method of claim 14, wherein detecting the signal comprises detecting a rate of change of the inductance; and determining displacer velocity comprises determining displacer velocity based on a maximum of the detected rate of change of the inductance. ### Claim 25 A flow metering system, comprising: a flowmeter prover, comprising: a displacer disposed in a flow tube, the flow tube comprising: a plurality of inductive transducers disposed along the length of the flow tube; a pulse generation circuit coupled to each transducer, the pulse generation circuit configured to generate a pulse having slope corresponding to a rate of change of inductance of the transducer produced by the displacer moving across the transducer. ### Claim 26 (depends on 25) The flow metering system of claim 25, further comprising a flowmeter coupled to the flowmeter prover. ### Claim 27 (depends on 25) The flow metering system of claim 25, wherein the flowmeter prover further comprises a signal analyzer coupled to the pulse generation circuit, the signal analyzer configured to: determine a position of the displacer in the flow tube based on a point of maximum slope of the pulse; identify a first detection point as a point of maximum slope of a rising edge of the pulse and a second detection point a point of maximum slope of a falling edge of the pulse; determine the velocity of the displacer based on the first detection point and the second detection point; determine whether the velocity of the displacer is uniform over the length of the flow tube based on determined velocity of the displacer as the displacer moves across each transducer; and determine a travel direction of the displacer in the flow tube based on the first detection point and the second detection point. ### Claim 28 (depends on 25) The flow metering system of claim 25, wherein the signal analyzer is further configured to verify performance of the flowmeter prover by at least one of: comparison of the time between the first detection point and the second detection point to previously recorded times between the first detection point and the second detection point at a given displacer velocity; verification of a plurality of volumes defined by one of the first and second detection points of one of the transducers and one of the first and second detection points of one of another of the transducers; and comparison of the signal generated by the signal conditioning circuit for each transducer at a given flow rate to stored baseline signals for each transducer at the given flow rate.