Dual Humidity Sensor Dew Point Measurement Without Sawtooth Drift
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Solution Overview
Problem
Existing dew point measurement technologies using capacitive humidity sensors suffer from inaccuracies and 'sawtooth effects' due to cyclic heating, leading to prolonged periods of incorrect readings and drift in dew point temperature, especially at low dew point values.
Innovation Solution
A measuring device with two humidity sensor units, one for determining dew point correction parameters and the other for continuous dew point measurement, thermally decoupled and controlled to ensure accurate dew point determination by correcting measurements using a controller.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If capacitive humidity sensors are cyclically heated to maintain calibration accuracy, then measurement precision is improved, but measurement continuity deteriorates due to gaps during heating and cooling phases
Solution Approach 1:
The system divides the humidity sensing function into two separate sensor units: a first humidity sensor unit that performs periodic heating and calibration, and a second humidity sensor unit that performs continuous measurement. This segmentation allows one sensor to be calibrated while the other continues measurement, eliminating measurement gaps.
Solution Approach 2:
The patent uses two identical humidity sensor units that can swap roles. When one sensor is heated for calibration, the other sensor takes over the measurement function. The sensors are designed to be interchangeable, allowing the system to maintain continuous measurement capability while performing periodic calibration.
2Reliability
If cyclical heating is applied to humidity sensors to correct drift, then measurement reliability is improved, but response time deteriorates due to delays during heating phases
Solution Approach 1:
By separating the calibration function (first humidity sensor unit) from the measurement function (second humidity sensor unit), the system ensures that measurement reliability is maintained through periodic calibration while response speed is preserved through continuous measurement capability of the second unit.
Solution Approach 2:
The controller continuously monitors the dew point temperature and can trigger calibration cycles based on detected drift or predetermined time intervals. This feedback mechanism ensures calibration is performed only when necessary, minimizing impact on response time while maintaining accuracy.
3Duration of action of moving object
If a single humidity sensor unit is used for continuous measurement, then measurement continuity is maintained, but measurement precision deteriorates due to cumulative drift errors
Solution Approach 1:
The system segments the measurement function into two sensor units, where one unit dedicated to calibration compensates for drift in the other unit dedicated to continuous measurement. This segmentation allows continuous measurement while maintaining precision through periodic calibration of the first unit.
Solution Approach 2:
The patent employs two identical sensor units that can function as backups for each other. The first unit serves as a calibration reference while the second unit provides continuous measurement, and they can swap roles as needed to maintain both continuity and precision.
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
Enables continuous and accurate dew point temperature measurement without gaps, eliminating the 'sawtooth effect' and ensuring rapid response to dew point changes.
Implementation Method 1
the controller is configured and arranged to change a temperature of the first humidity sensor unit via the temperature change element
Implementation Method 2
the change in capacitance of a suitable polymer is usually used as the measured variable for the relative humidity
Data Source
AI summary
A measuring device for determining and outputting a dew point temperature of an ambient medium, including a first and second humidity sensor unit and a controller. The first humidity sensor unit is configured to determine at least one dew point correction parameter and includes a first humidity sensor, a first temperature sensor and a temperature change element. The second humidity sensor unit, which is configured to continuously determine a dew point temperature and includes a second humidity sensor and a second temperature sensor. The controller is configured and arranged to change a temperature of the first humidity sensor unit via the temperature change element and thereby determine the dew point correction parameter, and use the dew point correction parameter from the first humidity sensor unit to correct measured values of the second humidity sensor unit and to continuously output corrected dew point temperatures based on the corrected measured values.