# US 6,843,137 B2 · Flowmeter fault detection > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 6,843,137 B2 - Document ID: US6843137B2 - Status: Granted - Kind: B2 - Application number: 10/059,277 - Filed: 2002-01-31 - Published: 2002-08-29 - Granted: 2005-01-18 - Earliest claimed: 2001-01-31 - Assignees: ABB AB - Inventors: Ray Keech - Web page: https://patentgrep.com/patent/US6843137B2 ## CPC - G01F 1/60: Circuits therefor - G01F 25/10: of flowmeters - G01F: MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME ## Abstract A previously unidentified problem of clipping in the input stages of flowmeter sensing circuitry has been identified and addressed. A solution is provided by flowmeter sensing circuitry, comprising: first and second inputs for connection to potential sensing electrodes positioned to measure a potential difference across the fluid which potential is representative of flow; differential amplifier means coupled to the first and second inputs for producing an output signal indicative of said potential difference across the fluid as a measure of flow; characterized by at least one voltage sensing means for sensing a voltage of at least one of the first and second inputs relative to a ground reference; and fault detecting means for detecting a potential fault if the voltage is outside a predetermined range. ## Claims ### Claim 1 Flowmeter sensing circuitry, comprising: first and second inputs for connection to potential sensing electrodes positioned to measure a potential difference across the fluid which potential is representative of flow; differential amplifier means coupled to the first and second inputs for producing an output signal indicative of said potential difference across the fluid as a measure of flow; characterised by at least one voltage sensing means for sensing a voltage of at least one of the first and second inputs relative to a ground reference; and fault detecting means for detecting a potential fault if the voltage is outside a predetermined range. ### Claim 2 (depends on 1) Flowmeter sensing circuitry according to claim 1, wherein the fault detecting means comprises means for storing a log of samples of the voltage over a period of time. ### Claim 3 (depends on 1) Flowmeter sensing circuitry according to claim 1, wherein the voltage sensing means and the fault detecting means are arranged to store samples at sampling intervals of one minute or less. ### Claim 4 (depends on 1) Flowmeter sensing circuitry according to claim 1, wherein the ground reference is connected to a ground reference of the differential amplifier. ### Claim 5 (depends on 1) Flowmeter sensing circuitry according to claim 1, wherein the fault detection means includes maximum and/or minimum detection means for obtaining a measure of maximum and/or minimum voltage over a sampling interval. ### Claim 6 (depends on 1) Flowmeter sensing circuitry according to claim 1, further including means for storing the or each measure of voltage together with a measure of meter output. ### Claim 7 (depends on 1) Flowmeter sensing circuitry according to claim 1, further including means for signalling an alarm in the event of detection of a fault or potential fault condition. ### Claim 8 (depends on 1) Flowmeter sensing circuitry according to claim 1, further including means for modifying the output of the meter in the event of detection of a fault or potential fault condition. ### Claim 9 (depends on 8) Flowmeter sensing circuitry according to claim 8, wherein the modifying means comprises means for switching to a default value, preferably zero. ### Claim 10 (depends on 8) Flowmeter sensing circuitry according to claim 8, wherein the modifying means comprises means for maintaining the output at a value based on the output value preceding detection of the fault. ### Claim 11 (depends on 1) Flowmeter sensing circuitry according to claim 1 including means for storing a measure of statistical information derived from samples. ### Claim 12 (depends on 1) Flowmeter sensing circuitry according to claim 1 including means for obtaining measurements of electrode voltage related to the phase of the local mains voltage. ### Claim 13 (depends on 1) Flowmeter sensing circuitry according to claim 1, wherein the differential amplifier has a high input impedance, preferably of the order of at least 1012 ohm. ### Claim 14 (depends on 1) Flowmeter sensing circuitry according to claim 1, wherein the voltage sensing means has an input impedance of at least the same order of magnitude as the differential amplifier. ### Claim 15 (depends on 1) Flowmeter sensing circuitry according to claim 1, wherein the predetermined range is selected based on an operational characteristic of the differential amplifier means. ### Claim 16 (depends on 1) Flowmeter sensing circuitry according to claim 1, wherein the predetermined range is selected based on a voltage with respect to ground at which clipping or distortion is liable to occur in the differential amplifier means. ### Claim 17 A method of detecting a potential fault in flowmeter sensing circuitry comprising first and second inputs for connection to potential sensing electrodes positioned to measure a potential difference across the fluid which potential is representative of flow and differential amplifier means coupled to the first and second inputs for producing an output signal indicative of said potential difference across the fluid as a measure of flow, the method comprising: sensing a voltage of at least one of the first and second inputs relative to a ground reference; and detecting a potential fault by detecting whether the voltage is outside a predetermined range. ### Claim 18 (depends on 17) A method according to claim 17, further comprising storing a log of samples of the voltage over a period of time. ### Claim 19 (depends on 17) A method according to claim 17, further comprising sampling the voltage at least once per sampling interval of one minute. ### Claim 20 (depends on 17) A method according to claim 17, including obtaining a measure of maximum and/or minimum voltage over a sampling interval. ### Claim 21 (depends on 17) A method according to claim 17, further including storing the or each measure of voltage together with a measure of meter output. ### Claim 22 (depends on 17) A method according to claim 17, further including signalling an alarm in the event of detection of a fault or potential fault condition. ### Claim 23 (depends on 17) A method according to claim 17, further including modifying the output of the meter in the event of detection of a fault or potential fault condition. ### Claim 24 (depends on 23) A method according to claim 23, wherein modifying comprises switching to a default value, preferably zero. ### Claim 25 (depends on 23) A method according to claim 23, wherein modifying comprises maintaining the output at a value based on the output value preceding detection of the fault. ### Claim 26 (depends on 17) A method according to claim 17, further including adjusting the phase at which measures of voltage are obtained relative to local mains voltage. ### Claim 27 (depends on 17) A method according to claim 17, wherein the predetermined range is selected based on an operational characteristic of the differential amplifier means. ### Claim 28 (depends on 17) A method according to claim 17, wherein the predetermined range is selected based on a voltage with respect to ground at which clipping or distortion is liable to occur in the differential amplifier means.