Air Flow Compensation in Room Temperature Transmitters
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Solution Overview
Problem
Existing room temperature transmitters (RTSs) in HVAC systems provide inaccurate temperature readings due to internal heating effects and air flow conditions, which are not adequately compensated, leading to significant measurement errors, especially in varying air flow scenarios.
Innovation Solution
An air flow compensated room temperature transmitter system that includes an air flow measurement unit with a known mass, resistive heating element, thermistor, and data transmission means to calculate cooldown time, which is used in a compensation formula to correct ambient temperature readings, incorporating data from both main and secondary sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If air flow isolation walls or structures are added to restrict air flow inside the RTS housing, then convection heat transfer is reduced and sensor readings are stabilized, but device complexity increases and installation flexibility is reduced
Solution Approach 1:
The invention extracts the air flow measurement function from the temperature measurement function by adding a separate air flow measurement unit. This unit independently measures air flow conditions and provides compensation data, allowing the temperature sensors to remain simple while achieving accurate measurements under varying air flow conditions through software-based compensation.
Solution Approach 2:
The air flow measurement unit acts as an intermediary that measures air flow conditions and uses this information to compensate temperature sensor readings. The unit includes a known mass, heating element, and thermistor that together measure air flow-induced cooling effects, which then compensates for measurement errors without requiring physical isolation structures.
2Measurement precision
If the main sensor is placed close to fresh air intake inside the housing, then the sensor measures ambient temperature more directly, but the sensor becomes more susceptible to air flow induced cooling effects and measurement errors
Solution Approach 1:
The invention implements feedback by continuously measuring air flow conditions with the air flow measurement unit and using this information to compensate temperature sensor readings. The system monitors the cooling effect on the known mass, calculates the air flow impact, and applies real-time compensation to the temperature measurements, creating a closed-loop system that maintains accuracy despite air flow variations.
3Adaptability or versatility
If internal heating elements are added to the RTS for air flow measurement, then air flow compensation becomes possible, but internal heating of electronics increases and affects sensor readings
Solution Approach 1:
The invention segments the heating function by dedicating a specific heating element solely to the air flow measurement unit, separate from the temperature sensing elements. This known mass with its heating element is thermally isolated from the main temperature sensors, allowing air flow measurement through controlled heating and cooling cycles without the heating affecting the temperature readings being compensated.
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 solution minimizes the impact of air flow on temperature measurements, maintaining high accuracy and reducing errors to within ±0.3°C, even in changing air flow conditions, compared to ±1.0°C without compensation, and allows for more flexible installation without the need for air flow-free environments.
Implementation Method 1
The at least one resistive heating element is configured to heat the known mass to an elevated temperature
Implementation Method 2
the thermistor is configured to measure temperature of the heated known mass during cooling for calculation of a cooldown time
Implementation Method 3
the thermistor is configured to measure temperature of the heated known mass during cooling
Implementation Method 4
Heat is generated on the printed circuit board due power losses in electronics. The heat transfers by convection and conduction to both sensors inside the housing.
Data Source
AI summary
The invention relates to an air flow measurement unit for an air flow compensated room temperature transmitter (RTS). The air flow measurement unit comprises a known mass, at least one resistive heating element, a thermistor, at least one heat sink, and data transmission means configured to transmit a resistance signal of the thermistor. The at least one resistive heating element is configured to heat the known mass to an elevated temperature and the thermistor is configured to measure temperature of the heated known mass during cooling for calculation of a cooldown time of the known mass defined based on the measured resistances. The invention further relates to an air flow compensated room temperature transmitter, an air flow measuring method for an air flow measurement unit, an air flow compensated ambient temperature measuring method for an air flow compensated room temperature transmitter and a computer program product.