Differential Thermometer Using Adjacent Sensor Segmentation
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Solution Overview
Problem
Conventional thermometers using a single temperature probe, such as thermistors, compromise sensitivity and fail to accurately measure small temperature variations, which is a limitation for medical and chemical applications requiring quick and precise temperature readings.
Innovation Solution
A thermometer utilizing a pair of adjacent temperature sensors, where one is pre-heated and the other is at ambient temperature, calculates temperature differences over time to determine the surface temperature, allowing for accurate and sensitive measurements through differential temperature measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If parallel resistors are used in the thermistor circuit to improve linearity, then temperature measurement speed is improved, but sensitivity is dramatically compromised
Solution Approach 1:
The single temperature measurement function is segmented into two separate measurement paths: one through the patient's body (via first thermistor) and one through air (via second thermistor). This segmentation allows the system to compare two different thermal pathways simultaneously, enabling accurate temperature measurement without requiring high sensitivity from individual thermistors when used in parallel resistor configurations.
Solution Approach 2:
The second thermistor acting as an air-path sensor serves as an intermediary reference that measures ambient temperature conditions. By comparing the temperature readings from both thermistors, the system can calculate the patient's body temperature while compensating for environmental factors, thereby maintaining measurement accuracy without sacrificing sensitivity.
2Device complexity
If a single temperature probe is used, then device complexity is reduced, but the ability to measure small temperature variations is lost
Solution Approach 1:
The measurement function is segmented into two separate thermistor sensors, each serving a specific purpose: the first thermistor measures temperature through the patient's body while the second thermistor measures ambient air temperature. This segmentation enables the detection of small temperature variations by comparing the differential readings between the two sensors.
Solution Approach 2:
Each thermistor is assigned a specific functional role: the first thermistor is optimized for body temperature measurement while the second thermistor is optimized for ambient temperature reference. This local quality assignment allows each sensor to operate in its optimal performance range, enhancing the overall ability to detect small temperature variations.
3Ease of manufacture
If conventional thermistor circuits are used, then manufacturing simplicity is maintained, but measurement accuracy for quick readings is compromised
Solution Approach 1:
The conventional single-thermistor circuit is segmented into two separate thermistor circuits, each with its own signal conditioning path. This segmentation allows the system to perform differential temperature measurement, improving accuracy for quick readings while maintaining manufacturing simplicity through the use of standard thermistor components and conventional circuit topologies.
Solution Approach 2:
The system changes the measurement parameter from absolute temperature measurement (single thermistor) to differential temperature measurement (two thermistors). By measuring the temperature difference between the body-path thermistor and air-path thermistor, the system achieves higher accuracy for quick readings while using standard manufacturing techniques.
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 enhances sensitivity and accuracy by using differential temperature measurements, providing precise temperature readings with high linearity over a small temperature range, reducing errors and the need for extensive calibration.
Implementation Method 1
The first and second thermistors are adapted for positioning against the surface... measures a temperature bC with the first thermistor at a first time t0 and a temperature bH with the second thermistor
Implementation Method 2
A programmable current source, positioned inside the housing, is provided for pre-heating the second thermistor to a pre-selected temperature
Data Source
AI summary
The thermometer using differential temperature measurements utilizes a pair of adjacent temperature sensors in order to measure the temperature of a common surface over a pre-selected period of time. The thermometer includes a housing and first and second thermistors mounted adjacent one another on the housing. The first and second thermistors are positioned against the surface, which can be a body part (for oral, rectal or axial body temperature measurements) or can be any other desired surface for which a spot check temperature reading is desired. A programmable current source pre-heats the second thermistor to a pre-selected temperature, while the first thermistor is initially at room temperature. A controller inside the housing causes both the first and second thermistors to take instantaneous temperature measurements of the surface at two successive times. The controller linearizes the measurements to predict the temperature of the surface, which is then displayed to the user.