Photodiode Detector Fault Current Compensation for Low-Temperature Thermometry
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Solution Overview
Problem
Existing noncontact, radiation thermometric temperature measurement methods struggle with accurately measuring low object temperatures below 75°C due to small photocurrents and temperature-dependent shunt resistances, leading to measurement errors or impossibility at temperatures <100°C, requiring temperature-stabilized detectors with high current consumption and long heating times.
Innovation Solution
A method and device that add a corrective current, controlled by a microcontroller, to compensate for the fault current caused by input bias current and input offset voltage of the current to voltage converter, across the temperature-dependent shunt resistance of the photodiode radiation detector, allowing accurate measurements at low radiant powers and eliminating the need for temperature stabilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If temperature-stabilized detectors are used to improve measurement precision at low temperatures, then measurement precision is improved, but current consumption increases and heating time is extended
Solution Approach 1:
The patent extracts and compensates only the specific fault current components (input bias current and input offset voltage effects) rather than stabilizing the entire detector temperature. The corrective current source isolates and counteracts the harmful electrical artifacts separately from the photodiode detection function, eliminating the need for thermal stabilization while maintaining measurement precision.
Solution Approach 2:
The patent changes the electrical parameters (corrective current magnitude and polarity) based on detected fault current characteristics rather than maintaining constant temperature. By dynamically adjusting the corrective current to match the temperature-dependent shunt resistance variations, the system achieves precision without thermal stabilization.
2Measurement precision
If temperature-stabilized detectors are used to improve measurement precision at low temperatures, then measurement precision is improved, but measurement time is extended due to long heating periods
Solution Approach 1:
The patent removes the temperature stabilization step entirely by extracting and compensating only the necessary electrical fault currents. This eliminates the time-consuming heating period while maintaining measurement precision through electrical correction rather than thermal control.
Solution Approach 2:
The patent applies preliminary electrical correction by adding the corrective current before measurement to counteract the fault currents. This preliminary electrical compensation replaces the preliminary thermal stabilization, enabling immediate measurements without heating delays.
3Device complexity
If conventional current to voltage conversion is used, then device complexity is reduced, but measurement precision deteriorates at low temperatures due to fault current influence
Solution Approach 1:
The patent introduces a corrective current source as an intermediary element between the photodiode and the current to voltage converter. This intermediary generates and injects the compensating current to neutralize the fault current effects, improving precision without complicating the core conversion function.
Solution Approach 2:
The corrective current source is controlled by a microcontroller that automatically adjusts the correction based on detected temperature and fault current characteristics. The system performs self-correction without requiring complex external stabilization equipment, maintaining simplicity while improving precision.
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
Enables accurate and quick temperature measurements at object temperatures as low as 50°C with improved precision and reduced current consumption, achieving measurement deviations of <±0.2 K across a range of 75°C to 200°C.
Implementation Method 1
photodiode radiation detector operating photovoltaically without bias voltage produces a short-circuit photocurrent which is proportional to the received radiant power
Implementation Method 2
This photocurrent is processed in a current to voltage converter whereupon a temperature signal is generated
Data Source
AI summary
In a method for noncontact, radiation thermometric temperature measurement, a short-circuit photocurrent that is proportional to a received radiant power is produced in a photodiode radiation detector that is operating photovoltaically without bias voltage. The photocurrent is processed in a current to voltage converter. Subsequently, a temperature signal corresponding to the radiant power is generated. A corrective current, dependent on a temperature of the photodiode radiation detector, is added to the short-circuit photocurrent to compensate a fault current, wherein the fault current is based on an input bias current and an input offset voltage of the current to voltage converter across a temperature-dependent shunt resistance of the photodiode radiation detector. A device with a corrective current source controlled by a microcontroller is provided that can be used to perform the method.