Environmental Sensor Cosmic Ray Dark Count Compensation
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Solution Overview
Problem
Particle counting systems face errors due to 'dark counts' caused by cosmic rays, which cannot be distinguished from particle-induced signals, leading to contamination detection inaccuracies in controlled environments.
Innovation Solution
A gaseous-fluid environmental sensor system that includes a particle count sensor, a cosmic ray sensor, and a controller to store dark counts and compensate particle counts, determining sensor faults by monitoring the absence of particle or cosmic ray detection over time, employing methods like dark count subtraction, coincidence detection, detector arrays, and estimated dark count subtraction to minimize errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a particle count sensor is used to detect particles in controlled environments, then particle contamination can be monitored, but dark counts caused by cosmic rays cannot be distinguished from particle signals, leading to measurement errors
Solution Approach 1:
A coincidence detector is introduced as an intermediary component that receives signals from both the particle count sensor and a cosmic ray detector. By requiring simultaneous signals from both detectors to register a count, the system mediates between particle detection and cosmic ray rejection, allowing accurate particle counting even in the presence of cosmic ray interference
Solution Approach 2:
The detection system is segmented into separate functional components: a particle count sensor for detecting particles, a cosmic ray detector for detecting cosmic rays, and a coincidence detector for integrating both signals. This segmentation allows each component to be optimized for its specific detection task while working together to solve the overall measurement problem
2Reliability
If the photodetector is optimized for photon detection from particles, then particle signals are enhanced, but the photodetector cannot distinguish these signals from cosmic ray-induced dark pulses
Solution Approach 1:
The coincidence detector serves as an intermediary that processes signals from both the optimized photodetector and the cosmic ray detector. It requires coincident signals from both detectors before registering a particle count, thereby maintaining the reliability of photon detection while achieving precise discrimination against cosmic ray false positives
Solution Approach 2:
The system uses feedback from the cosmic ray detector to modulate the counting behavior of the particle count sensor. When the cosmic ray detector registers activity, the coincidence detector adjusts its counting criteria, providing dynamic feedback that improves signal discrimination accuracy while maintaining detection reliability
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 system effectively reduces errors in particle counting by accurately differentiating between particle and cosmic ray-induced signals, ensuring reliable contamination monitoring and reducing false alarms in clean environments.
Implementation Method 1
The photodetector, typically a PIN photo diode converts the photons to a current that produces a voltage that is a function of particle size
Implementation Method 2
Cosmic rays, which include gamma rays and x-rays, are forms of radiation that can also cause a pulse of current to occur when they intercept the photodetector
Data Source
AI summary
A gaseous-fluid environmental sensor having a gaseous-fluid flow system. The gaseous-fluid flow system, in one construction, includes a blower to move the gaseous fluid from an intake port to an exhaust port via a flow path. The gaseous-fluid environmental sensor further includes a controller coupled to a particle count sensor. The controller determines whether the particle count sensor has a fault based on the particle count sensor not sensing a particle or a cosmic ray in a time period.