Electronic Psychrometer With Evaporation Control for Low Temperature Humidity
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Solution Overview
Problem
Current humidity sensing equipment lacks precision and reliability in low temperature and high humidity environments, particularly in the range of 80-100% RH, leading to reduced accuracy and potential mechanical or electronic failures.
Innovation Solution
An electronic psychrometer system with high accuracy 10 kOhm thermistors and a programmable controller, coupled with a computer-readable medium, calculates relative humidity with ±1% RH accuracy at 32 degrees F, using a fan-less evaporator cage and calibration method to ensure precise wet and dry bulb temperature measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional moisture absorbing capacitance sensors are used for humidity measurement, then the device is simple and easy to manufacture, but the measurement precision deteriorates to +/−5% RH at low temperatures and high humidity (80-100% RH range)
Solution Approach 1:
The patent replaces traditional mechanical capacitance-based humidity sensors with an electronic psychrometer system that uses temperature sensing (thermistors) and computational algorithms to calculate humidity. This substitution of mechanical sensing with electronic measurement and calculation achieves superior precision (+/−1% RH) while maintaining practical device complexity through integrated circuitry and software processing.
2Reliability
If capacitance sensors operate in high humidity range (80-100% RH), then they can cover the required measurement range, but reliability deteriorates due to mechanical failure and electronic failure
Solution Approach 1:
The patent replaces moisture-absorbing mechanical capacitance sensors with an electronic temperature-based measurement system. By measuring dry and wet bulb temperatures with thermistors and calculating relative humidity through psychrometric relationships, the system achieves reliable operation across the full 0-100% RH range without the mechanical failure modes that plague capacitance sensors in high humidity environments.
Solution Approach 2:
The patent changes the measurement parameter from direct moisture content detection (capacitance) to temperature-based indirect measurement (psychrometry). By measuring temperature differences between dry and wet bulb sensors and using the psychrometric relationship, the system achieves both full humidity range coverage and enhanced reliability, as temperature measurement is fundamentally more reliable than capacitance measurement in high humidity conditions.
3Measurement precision
If thermistors are used for temperature sensing in the psychrometer, then measurement precision improves to +/−1% RH, but device complexity increases due to programmable controller and calibration requirements
Solution Approach 1:
The patent employs a programmable microcontroller that performs multiple functions: reading thermistor resistance values, converting resistance to temperature, performing psychrometric calculations to determine relative humidity, storing calibration data, and potentially controlling humidification/dehumidification equipment. This multi-functional integration achieves high measurement precision while managing electronic complexity through a single coordinated processing unit rather than separate dedicated circuits for each function.
Solution Approach 2:
The patent incorporates calibration procedures that are performed in advance to establish accurate relationships between thermistor resistance and temperature, and to account for specific sensor characteristics. By performing calibration beforehand and storing the results in the microcontroller's memory, the system achieves +/−1% RH precision without requiring complex real-time adjustment mechanisms during normal operation, thus managing complexity through preliminary setup rather than ongoing complexity.
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
The system provides precise and reliable humidity measurement and control, enabling effective operation of humidifiers and dehumidifiers in low temperature, high humidity conditions, avoiding mechanical and electronic failures.
Implementation Method 1
The wet bulb thermometer has a water saturated wick around it. When the thermometer is swung in the air to move air over the wet bulb, evaporation of water from this wick depresses the temperature of the bulb
Implementation Method 2
high accuracy 10 kOhm thermistors and a programmable controller, coupled with a computer-readable medium, calculates relative humidity with ±1% RH accuracy at 32 degrees F
Data Source
AI summary
The present invention has to do with a method and system for a high precision electronic psychrometer operable at low temperatures and high humidity environments. The electronic psychrometer includes thermistors for measuring wet and dry bulb temperatures and a wicked cage surrounding one of the thermistors. The wicking action of the wicked cage is controlled by an evaporation controller in conjunction with the wick's physical parameters. The electronic psychrometer determines relative humidity and provides a readout display and/or a control signal.