IR Sensor Filter Arrangement for Low Power CO2 Detection
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Solution Overview
Problem
Existing IR sensors, such as CO2 sensors, have high power requirements and are unsuitable for battery-operated use due to the need for a radiation source with a heating-up period, limiting their portability and usability.
Innovation Solution
A gas sensor configuration with a filter arrangement where one filter's passband is within the other's, allowing one detector to capture IR radiation including the gas's absorption spectrum and another detector capturing a sub-range without it, forming a signal difference to enhance sensitivity and reduce power consumption, using ambient IR radiation instead of a dedicated source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a dedicated IR radiation source is used, then measurement capability is improved, but power consumption increases and portability decreases
Solution Approach 1:
The sensor system uses ambient IR radiation from the environment as its own energy source, eliminating the need for an external powered IR radiation source. The detectors capture ambient IR radiation that passes through the gas sample, allowing the system to self-power the measurement process without requiring battery operation or external power supply for the radiation source.
Solution Approach 2:
The ambient IR radiation serves multiple functions simultaneously: it acts as both the energy source for the measurement and the medium through which the gas absorption occurs. The same environmental radiation that would normally be considered background noise becomes the functional irradiation source, enabling the sensor to perform CO2 detection without dedicated power consumption for radiation generation.
2Measurement precision
If a dedicated IR radiation source is used, then measurement capability is improved, but device portability decreases due to heating-up period requirements
Solution Approach 1:
The system eliminates the heating-up period requirement by using ambient IR radiation that is already present in the environment. No dedicated radiation source needs to be activated, warmed up, or stabilized before measurement can begin. The sensor can immediately start detecting CO2 concentrations as ambient radiation naturally passes through the sample.
Solution Approach 2:
The ambient IR radiation is already in place and ready for measurement before the sensor is activated. The environment provides the necessary radiation source in advance, eliminating the need for pre-heating or activation periods that would otherwise be required before the sensor becomes operational.
3Measurement precision
If filters are arranged to capture overlapping spectral ranges, then sensitivity is improved, but device complexity increases
Solution Approach 1:
The spectral range is divided into two distinct bands using separate filters: a first filter for capturing IR radiation in a first spectral range and a second filter for a second spectral range. This segmentation allows each detector to specialize in a specific band while the overlapping ranges enable comparative measurement for improved sensitivity through ratio calculation.
Solution Approach 2:
Instead of using a single detector measuring absolute intensity, the system introduces a dimensional comparison by measuring the same gas sample through two different spectral filters simultaneously. The sensitivity enhancement comes from the ratio of the two measurements rather than from absolute signal strength, adding a comparative dimension to the detection process.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration increases sensitivity, reduces power consumption, allowing battery operation and enabling wireless transmission, while providing more accurate CO2 monitoring and additional data like temperature and room occupancy information.
Implementation Method 1
CO2 absorbs infrared radiation, that is to say the content of IR radiation in a specific, narrowly defined wavelength range is a quantity that can be used for determining the CO2 concentration
Implementation Method 2
The detector arrangement has two detectors, each of which is associated with a filter
Data Source
AI summary
An IR sensor (1), especially a CO2 sensor, is described, having a filter arrangement (6), downstream of which there is arranged a detector arrangement (7), and an evaluating device (8) which is connected to the detector arrangement (7), the filter arrangement (6) having a first filter (9) and a second filter (10), which are configured as bandpass filters and each have a passband and of which the first filter (9) allows passage of a predetermined IR band and the second filter (10) does not, and the detector arrangement having two detectors (14, 15), each of which is associated with a filter (9, 10). The objective is to simplify the use of such an IR sensor. For that purpose, the passband of one filter (10) is arranged within the passband of the other filter (9) and the evaluating device (8) forms the difference of the signals (S1, S2) of the detectors (14, 15) and normalises it to the signal (S1) of a detector (14).