External Temperature Sensor Placement for Rapid Ambient Detection
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Solution Overview
Problem
Traditional printed circuit board (PCB) mounted temperature sensors experience significant lag time in achieving temperature equilibrium, which can range from minutes to over 30 minutes, due to manufacturing tolerances, air gaps, and insulation properties, and are often affected by internal heat generation or dissipation.
Innovation Solution
A temperature sensor is placed externally with respect to the device's housing using a flexible printed circuit substrate with a protective layer, allowing for reduced lag time in ambient temperature detection by avoiding internal heat influences and manufacturing variations, and eliminating reliance on thermal interface materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the temperature sensor is mounted inside the device housing on the PCB, then the sensor is protected and integrated into the device structure, but the sensor experiences significant lag time (minutes to over 30 minutes) in detecting ambient temperature due to thermal equilibrium requirements
Solution Approach 1:
The temperature sensor is extracted from the internal PCB mounting location and repositioned to an external location on the device housing. This allows the sensor to directly contact the external environment through a pass-through region, eliminating the thermal lag caused by the housing and internal components while maintaining sensor protection through the thin protective layer.
2Temperature
If thermal interface materials are used to improve thermal contact between the sensor and housing, then thermal conductivity is improved, but manufacturing tolerances and air gaps still cause significant lag time
Solution Approach 1:
A thin protective layer is applied over the temperature sensor when it is positioned externally on the housing. This thin film provides necessary environmental protection while minimizing thermal resistance, allowing rapid heat transfer between the sensor and ambient environment without the lag associated with thicker thermal interface materials.
3Loss of time
If the temperature sensor is placed externally on the housing, then the lag time in detecting ambient temperature is significantly reduced, but the sensor becomes more vulnerable to environmental damage
Solution Approach 1:
A protective layer is applied beforehand over the externally positioned temperature sensor. This protective layer acts as a cushion or barrier against environmental harmful factors such as dust, moisture, and physical damage, while being thin enough to maintain rapid thermal response characteristics.
4Power
If internal components generate or dissipate heat, then device functionality is maintained, but the interior temperature never reaches equilibrium with the ambient environment
Solution Approach 1:
The temperature sensor is extracted from the internal environment where heat generation and dissipation from components prevent thermal equilibrium, and repositioned to the external environment. This ensures the sensor measures true ambient temperature without being influenced by internal heat sources or sinks.
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 enables accurate and rapid ambient temperature measurement with reduced lag time, unaffected by internal heat or manufacturing tolerances, and provides improved measurement accuracy and reliability.
Implementation Method 1
The temperature sensor can be secured to an internal printed circuit board through a flexible printed circuit substrate, and may be covered with a protective layer. Placing the temperature sensor externally with respect to the device's housing significantly reduces the lag time in detecting the ambient temperature.
Implementation Method 2
The protective layer does not substantially affect the lag time due to the thinness of the layer, due to the material properties of the protective layer such as its thermal conductivity, or due to the combination of the protective layer's thinness and material properties.
Data Source
Figure 1A~1B
Figure 2
AI summary
Methods, systems, and apparatus, including computer programs encoded on computer-storage media, for a device with improved ambient temperature detection. In some implementations, a device includes a housing that forms an interior space, and the housing includes an exterior surface, a pass-through region that defines a through-hole between the interior space to the exterior surface, and a recess at the exterior surface adjacent to the pass-through hole. The device includes a printed circuit board disposed within the interior space of the plastic housing.