Multi-Sensor Microwave Temperature Probe for Even Food Heating
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Solution Overview
Problem
Microwave-assisted cooking ovens face issues with temperature measurement accuracy due to electromagnetic interference and uneven heating, where the core temperature probe overheats and causes surface charring or drying, while the inner core remains undercooked due to microwave penetration attenuation.
Innovation Solution
A food cooking oven with a needle-like core temperature probe equipped with sensors at different depths, including an outermost sensor to monitor the surface temperature, and control means to adjust microwave power based on temperature comparisons to prevent overheating and ensure even cooking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a needle-like core temperature probe is inserted in the food to detect core temperature, then temperature measurement capability is improved, but the probe body and connection cable are overheated by microwave energy causing measurement errors and food surface charring
Solution Approach 1:
The temperature probe is divided into multiple sensing elements positioned at different depths (surface, intermediate, and core positions) along the probe rod. This segmentation allows simultaneous measurement of temperatures at various locations without requiring a single long probe exposed to microwaves throughout its length, reducing overall probe overheating while maintaining measurement capability.
Solution Approach 2:
A dielectric member is introduced as an intermediary between the probe connection cable and the food item. This dielectric member acts as a barrier that reduces microwave energy coupling to the probe cable, thereby minimizing probe overheating and electromagnetic interference while still allowing the probe to function effectively for temperature measurement.
2Productivity
If microwave power is increased to cook the inner core of dense food items, then cooking speed is improved, but the outer surface layer becomes overcooked, charred or dried out
Solution Approach 1:
The control system continuously receives temperature signals from multiple sensors positioned at different depths of the food item and dynamically adjusts microwave power output based on real-time temperature feedback. When surface temperature approaches the predetermined threshold, the system automatically reduces power to prevent charring while maintaining adequate power for core cooking, thus resolving the contradiction between cooking speed and surface temperature control.
3Reliability
If a shielding sheath is provided on the probe connection cable to reduce electromagnetic interference, then signal quality is improved, but the shielding length must be precisely nl/2 which complicates manufacturing and installation
Solution Approach 1:
Instead of requiring precise shielding length matching (nl/2), the invention introduces a dielectric member with specific permittivity properties that provides electromagnetic isolation without stringent dimensional requirements. This parameter-based approach (using dielectric constant rather than physical dimensions) simplifies manufacturing and installation while maintaining signal quality and reducing probe overheating.
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 solution allows for precise temperature control, preventing surface overcooking and ensuring even heating throughout the food item, improving cooking accuracy and preventing spoilage by adjusting microwave power according to surface and core temperatures.
Implementation Method 1
at least three temperature sensors (5, 6, 7, 15) distributed inside the rod (4) at different depths, in particular also in the outermost region of the food item (3)
Implementation Method 2
generating a very intense microwave field within the cooking cavity causes the mass or body of the food item being cooked to undergo a rather uneven heating
Implementation Method 3
providing a reflecting screen to be arranged at an appropriate distance on the core-temperature probe rod, so as to work as a shield preventing microwaves from affecting the probe introduction zone
Implementation Method 4
the heat being generated on the needle-like core temperature probe converts into a considerable rise in the temperature thereof, which most obviously is then transferred by conduction exactly to said outer surface layer of the food
Data Source
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AI summary
Food cooking oven comprising a cooking cavity, means adapted to generate and irradiate microwaves for propagation inside said cooking cavity, control means adapted to process signals received from external sources, and to govern said microwave generating and irradiating means for operation in accordance with the signals being received from said external sources, a movable temperature probe, preferably in the shape of a needle-like core temperature probe, adapted to be introduced in the food item placed inside said cooking cavity of the oven, and provided with a plurality of temperature sensors that are distributed at pre-determined distances from each other along said movable probe, said sensors being electrically connected to said control means to supply them with said signals from external sources, said control means being adapted to receive and process the temperature signal coming from a pre-determined one of said sensors, usually the one corresponding to the outermost layer of the food item, and to modify the operation of said microwave generating and irradiating means based on the course of said temperature signal.