Optical Turbidity Sensor with Dual-Path Temperature Compensation
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Solution Overview
Problem
Conventional turbidity sensors in domestic appliances suffer from temperature-dependent fluctuations in measurement signals, leading to unreliable turbidity readings due to varying temperatures during washing or dishwashing cycles.
Innovation Solution
A sensor arrangement with two light-measuring paths is implemented, where one path is exposed to the turbid medium for turbidity measurement and another path, acting as a reference, is isolated from the medium but subject to similar temperature conditions, allowing for temperature compensation by calculating differences or quotients between the two measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single light-measuring path is used for turbidity measurement, then the device complexity is low, but the measurement precision deteriorates due to temperature-dependent fluctuations
Solution Approach 1:
The single light-measuring path is segmented into two separate paths: a first light-measuring path for turbidity measurement and a second light-measuring path for temperature reference. This segmentation allows the system to distinguish between signal changes caused by turbidity and those caused by temperature variations, thereby improving measurement precision while maintaining relatively simple device complexity through modular path separation.
Solution Approach 2:
The second light-measuring path acts as an intermediary reference that does not directly measure turbidity but provides temperature compensation data. This intermediary path enables the system to correct temperature-dependent fluctuations in the primary measurement path, improving overall measurement accuracy without requiring direct intervention in the turbidity measurement process.
2Reliability
If the sensor is placed in direct contact with working water for measurement, then the measurement reliability is improved, but the stability of the sensor components deteriorates due to temperature exposure
Solution Approach 1:
The sensor system is segmented into two spatially separated light-measuring paths: the first path extends into the working water for reliable turbidity measurement, while the second path remains within the sensor housing to protect components from temperature exposure. This segmentation allows the sensor to maintain both measurement reliability and component stability simultaneously.
Solution Approach 2:
The reference measurement function is extracted from the primary measurement path and placed in a separate second light-measuring path that remains inside the sensor housing. This extraction allows the reference path to provide temperature compensation data without exposing the sensor components to the harsh thermal environment of the working water, thereby maintaining component stability.
3Measurement precision
If temperature compensation is implemented using a reference path, then the measurement precision is improved, but the device complexity increases due to additional components
Solution Approach 1:
Both the turbidity measurement function and the temperature reference function are merged into a single sensor housing with integrated light sources and detectors. The first and second light-measuring paths share common components such as the light-emitting component arrangement and signal evaluation unit, reducing overall device complexity while still providing temperature-compensated measurements.
Solution Approach 2:
The sensor system is designed with multi-functionality where the same light-emitting component arrangement serves both the first light-measuring path for turbidity measurement and the second light-measuring path for temperature reference. This universal use of components reduces the total number of parts required and simplifies the device structure while achieving temperature compensation.
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 approach provides consistently reliable turbidity measurements by eliminating temperature-dependent errors while maintaining turbidity information, ensuring accurate control of domestic appliance operations.
Implementation Method 1
a light-emitting component arrangement and two light-receiving elements
Implementation Method 2
a first transports light from the light-emitting component arrangement to a first of the light-receiving elements
Implementation Method 3
the second light-measuring path transports light from the light-emitting component arrangement to the second of the light-receiving elements
Data Source
AI summary
A sensor suitable for optical turbidity measurements is described. The sensor is suitable for use in a water-bearing domestic electrical appliance (e.g. washing machine or dishwasher) and allows the temperature dependence of the turbidity measurements obtained by means of a first light detector to be compensated for. To this end, the sensor implements, in addition to a turbidity-measuring path along which a measuring-light beam is sent through a measuring space containing the turbid medium to a first light detector, a reference measuring path along which a reference light beam is transported to a second light detector which is thermally coupled with the first light detector. A heat-equalizing element can ensure that any temperature differences between the two light detectors are minimized. Both light-measuring paths can run in some regions inside the same solid-material light-conducting structure.