Patent ID: 11946810
Assignee: JONDETECH SENSORS AB (PUBL)
Field: Measurement (Instruments)
Classification: CPC G | IPC G

Claim 10:
11. A system comprising an IR sensor which is a thermopile, a processor and a memory, the system comprising a signal processing module, a threshold determination logic and presence determination logic, the system being configured store a first state or a second state as present state data in the memory where the first state indicates that a person is not present and the second state indicates that a person is present, the system being further configured to use the IR sensor to determine IR sensor data during a first time period and provide the IR sensor data to the signal processing module, the signal processing module being configured to use the IR sensor data to determine a smoothed IR signal for the time period, and determine the variability of the IR sensor data, the threshold determination logic being configured to use the determine a smoothed IR signal and the variability of the IR background signal level to, when the system is in the first state as determined by the system, determine a first threshold with a value higher than the smoothed IR signal in such a way so that greater variability in the IR background signal results in a higher threshold, and
when the system is in the second state as determined by the system determine a second threshold with a value lower than the smoothed IR signal in such a way so that greater variability in the IR background signal results in a lower threshold,
the presence determination logic being configured to use the thresh-old to when further IR sensor data is received
when the system is in the first state, switch the state to the second state when the further IR sensor data comprises a value that is higher than the first threshold, and when the system is the second state, switch the state to the first state when the further IR sensor data comprises a value lower than the second threshold, where the system is configured to repeatedly determine the state.