# US 12,761,085 B2 · Response of heat detectors with surface mounted thermistors > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,761,085 B2 - Document ID: US12761085B2 - Status: Granted - Kind: B2 - Application number: 18/520,854 - Filed: 2023-11-28 - Published: 2025-05-29 - Granted: 2026-10-13 - Earliest claimed: 2023-11-28 - Assignees: Honeywell International Inc. - Applicants: Honeywell International Inc. - Inventors: Massimo Bressanutti; Daniele Iurissevich; Borut Jogan - Web page: https://patentgrep.com/patent/US12761085B2 ## CPC - G01K 3/14: in respect of space - G01K 7/22: the element being a non-linear resistance, e.g. thermistor (G01K7/26 takes precedence) - G01K: MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR (radiation pyrometry G01J5/00) ## Abstract Devices, systems, and methods for providing point heat detectors based on surface mounted thermistors are described herein. One point heat detector of a fire sensing system, includes a circuit board body having number of corners, at least two surface mounted thermistors, each thermistor mounted on different ones of the corners, an intermediate position between two of the surface mounted thermistors, and a processor that executes instructions stored in memory to determine a temperature for at least one of the two surface mounted thermistors and the intermediate position. ## Claims ### Claim 1 A point heat detector of a fire sensing system, comprising: a circuit board body having a number of corners; at least two surface mounted thermistors, wherein each of the at least two surface mounted thermistors are mounted on a different corner of the number of corners; an intermediate position between two of the at least two surface mounted thermistors; and a processor that executes instructions stored in memory to: determine a temperature for at least one of the at least two surface mounted thermistors; and determine an estimated temperature for the intermediate position between the two of the at least two surface mounted thermistors using a proportional integral observer (PIO) process. ### Claim 2 (depends on 1) The point heat detector of claim 1, wherein the processor is firmware. ### Claim 3 (depends on 1) The point heat detector of claim 1, wherein the processor and memory are on the circuit board body. ### Claim 4 (depends on 1) The point heat detector of claim 1, wherein the temperature is a measured temperature. ### Claim 5 (depends on 1) The point heat detector of claim 1, wherein each of the at least two surface mounted thermistors have a measured temperature. ### Claim 6 (depends on 1) The point heat detector of claim 1, wherein each of the at least two surface mounted thermistors and the intermediate position have a thermal inertia and wherein the processor executes the instructions stored in the memory to apply a temperature compensation adjustment factor to each thermal inertia. ### Claim 7 (depends on 1) The point heat detector of claim 1, wherein a calculation of the temperature is calculated via a proportional integral observer model. ### Claim 8 (depends on 1) The point heat detector of claim 1, wherein the intermediate position has an estimated thermal inertia calculated from the estimated temperature. ### Claim 9 (depends on 1) The point heat detector of claim 1, wherein the circuit board body has a surface mounted thermistor of the at least two surface mounted thermistors mounted at each corner of the circuit board body. ### Claim 10 (depends on 9) The point heat detector of claim 9, wherein the point heat detector has intermediate positions including the intermediate position defined between each of the at least two surface mounted thermistors. ### Claim 11 A point heat detector of a fire sensing system, comprising: a circuit board body having a number of corners; at least two surface mounted thermistors, wherein each of the at least two surface mounted thermistors are mounted on a different corner of the number of corners; an intermediate position between two of the at least two surface mounted thermistors; and a processor that executes instructions stored in memory to: determine a temperature for at least one of the at least two surface mounted thermistors; determine an estimated temperature for the intermediate position between the two of the at least two surface mounted thermistors using a proportional integral observer (PIO) process; determine a thermal inertia for each of the at least two surface mounted thermistors and the intermediate position; determine a temperature compensation adjustment factor to each thermal inertia; and apply the temperature compensation adjustment factor to the estimated temperature. ### Claim 12 (depends on 11) The point heat detector of claim 11, wherein a controller analyzes a time value that data was received to determine a direction of a heat source. ### Claim 13 (depends on 12) The point heat detector of claim 12, wherein the controller compares data received from the thermistors to determine the direction of the heat source. ### Claim 14 (depends on 12) The point heat detector of claim 12, wherein the point heat detector has surface mounted thermistors mounted on four corners and wherein the controller combines data received from the thermistors to determine the direction of the heat source. ### Claim 15 (depends on 12) The point heat detector of claim 12, wherein the point heat detector includes a digital compass and wherein the controller combines data received from the thermistors and the digital compass to determine the direction of the heat source. ### Claim 16 A point heat detector of a fire sensing system, comprising: a circuit board body having a number of corners; at least two surface mounted thermistors, wherein each of the at least two surface mounted thermistors are mounted on a different corner of the number of corners; an intermediate position between two of the at least two surface mounted thermistors; and a processor that executes instructions stored in memory to: determine a temperature for at least one of the at least two surface mounted thermistors; determine an estimated temperature for the intermediate position between the two of the at least two surface mounted thermistors using a proportional integral observer (PIO) process; determine a thermal inertia for each of the at least two surface mounted thermistors and the intermediate position; determine a temperature compensation adjustment factor to each thermal inertia through use of the PIO process; and apply the temperature compensation adjustment factor to the estimated temperature. ### Claim 17 (depends on 16) The point heat detector of claim 16, wherein a controller compares a measured thermistor temperature with an estimated thermistor temperature to determine a model thermistor temperature. ### Claim 18 (depends on 17) The point heat detector of claim 17, wherein the controller determines a difference value by comparing the measured thermistor temperature with the estimated thermistor temperature. ### Claim 19 (depends on 18) The point heat detector of claim 18, wherein the controller uses the difference value to update a sensor model. ### Claim 20 (depends on 18) The point heat detector of claim 18, wherein the controller uses the difference value to update an air flow temperature estimating model.