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

Claim 0:
1. A method for determining presence of a person, the method involving a system which can be in a first state indicating that a person is not present and a second state indicating that a person is present, the method is carried out repeatedly and comprising the steps:
a) receiving IR sensor data during a first time period from a thermopile and using the IR sensor data to determine a smoothed IP signal for the time period, and determining a variability of the IR sensor data, then
b) using the 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 and in such a way so that greater variability in the IR background signal results in a higher threshold, and when the system is the second state as determined by the system, determine a second threshold with a lower value than the smoothed IR signal and in such a way so that greater variability in the IR background signal results in a lower threshold, then
c) receiving further IR sensor data during a second time period, which is after the first time period, and using the further IR sensor data, 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.