# US 5,682,145 A · Toxic gas detector with a time measurement sensor > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,682,145 A - Document ID: US5682145A - Status: Granted - Kind: A - Application number: 08/497,943 - Filed: 1995-06-30 - Granted: 1997-10-28 - Earliest claimed: 1995-06-30 - Assignees: Sensor Tech, Inc. - Inventors: Gerald Patrick Sweetman; Gary Ross Mitchell; Marcus Leroy Caldwell; William Louis Witt - Web page: https://patentgrep.com/patent/US5682145A ## CPC - G01N 33/004: {CO or CO2} - G01N 27/122: {Circuits particularly adapted therefor, e.g. linearising circuits} - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) ## Abstract The present invention is a carbon monoxide or other toxic gas detector. The detector of the present invention detects the presence of carbon monoxide in an air sample by measuring the time required for the sensor circuitry to charge. Such a measurement technique eliminates the inaccuracies inherent in prior art detectors which measure the resistance of the sensor circuitry upon exposure to carbon monoxide. The detector of the present invention is controlled by a microprocessor which enables the detector to retain in memory air sample readings of carbon monoxide or other toxic gas. If the detector registers four consecutive readings which indicate the presence of carbon monoxide in an air sample in a concentration greater than or equal to about 100 ppm, then the alarm of the detector will be triggered, thereby alerting the user to a dangerous concentration of carbon monoxide gas in the air. Such a detection cycle enables the detector to detect not only high level, lethal concentrations of carbon monoxide in the air, but also, chronic, low level harmful concentrations of carbon monoxide in the air. ## Claims ### Claim 1 A gas detector comprising the elements of: a. a gas sensor; b. a capacitor; c. a transformer; d. a gated time measuring device; and e. a permanent memory chip; all of which are interconnected by means of and are integral with a circuit board wherein the gated time measuring device measures a time for the capacitor to charge, which time measurement value is an indicator of the presence of a gas. ### Claim 2 (depends on 1) A detector as claimed in claim 1 further comprising an audio alarm. ### Claim 3 (depends on 1) A detector as claimed in claim 1 further comprising a visual alarm. ### Claim 4 (depends on 1) A detector as claimed in claim 1 further comprising a casing for housing the detector elements. ### Claim 5 (depends on 1) A detector as claimed in claim 1 wherein the capacitor and sensor are in a series circuit with each other. ### Claim 6 (depends on 1) A detector as claimed in claim 1 wherein the gated time measuring device is a microprocessor. ### Claim 7 (depends on 1) A detector as claimed in claim 1 wherein the detector may be reset. ### Claim 8 (depends on 6) A detector as claimed in claim 6 wherein the microprocessor will register an alarm state if a gas concentration in an air sample is greater than or equal to about a pre-determined concentration. ### Claim 9 (depends on 8) A detector as claimed in claim 8 wherein the microprocessor will trigger and flash a visual alarm for each alarm state. ### Claim 10 (depends on 9) A detector as claimed in claim 9 wherein the microprocessor will trigger an audio alarm upon four consecutive alarm state registrations. ### Claim 11 (depends on 6) A detector as claimed in claim 6 wherein the microprocessor will trigger an audio alarm and a visual alarm upon detection of a pre-determined gas concentration in an air sample. ### Claim 12 (depends on 6) A detector as claimed in claim 6 wherein the microprocessor makes a time measurement about every two and one half minutes. ### Claim 13 (depends on 6) A detector as claimed in claim 6 wherein the gas is carbon monoxide. ### Claim 14 (depends on 13) A detector as claimed in claim 13 wherein the sensor is selected from the group consisting of a tin dioxide sensor and a copper manganese dioxide sensor. ### Claim 15 (depends on 14) A detector as claimed in claim 14 wherein the microprocessor screens out transient hydrocarbon exposure events to the sensor. ### Claim 16 A carbon monoxide detector comprising the elements of: a. a toxic gas sensor; b. a capacitor; c. a transformer; d. a gated measuring device; e. a permanent memory chip; f. an audio alarm; g. a visual alarm; and h. a power source all of which are interconnected by means of and are integral with a circuit board, wherein all of the elements are housed in a casing, wherein the capacitor and the sensor are in a series circuit with each other and wherein the gated time measuring device measures a time for the capacitor to charge, which time measurement value is an indicator of the presence of carbon monoxide. ### Claim 17 (depends on 16) A detector as claimed in claim 16 wherein the gated time measuring device is a microprocessor. ### Claim 18 (depends on 17) A detector as claimed in claim 17 wherein the sensor is selected from the group consisting of a tin dioxide sensor and a copper manganese dioxide sensor. ### Claim 19 (depends on 16) A detector as claimed in claim 16 wherein the detector may be reset. ### Claim 20 (depends on 17) A detector as claimed in claim 17 wherein the microprocessor will register an alarm state if a carbon monoxide concentration in an air sample is greater than or equal to about 100 ppm. ### Claim 21 (depends on 20) A detector as claimed in claim 20 wherein the microprocessor will trigger and flash a visual alarm for each alarm state. ### Claim 22 (depends on 21) A detector as claimed in claim 21 wherein the microprocessor will trigger an audio alarm upon four consecutive alarm state registrations. ### Claim 23 (depends on 17) A detector as claimed in claim 17 wherein the microprocessor will trigger an audio alarm and a visual alarm upon detection of a lethal carbon monoxide concentration in an air sample. ### Claim 24 (depends on 17) A detector as claimed in claim 17 wherein the microprocessor makes a time measurement about every two and one half minutes. ### Claim 25 (depends on 17) A detector as claimed in claim 17 wherein the microprocessor screens out transient hydrocarbon exposure events to the sensor. ### Claim 26 (depends on 16) A detector as claimed in claim 16 further comprising a thermistor wherein the thermistor compensates for air temperature and humidity changes in an environment in which the detector is located.