Radiation Pulse Selection Circuit With Crystal-Clock Timing
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Solution Overview
Problem
Conventional radiation measurement devices experience instability in pulse width and delay time due to variations in resistor and capacitor characteristics, leading to count loss and errors in measurement results.
Innovation Solution
A radiation measurement device incorporating a crystal oscillator for generating a stable clock pulse, combined with first and second rising and falling detection circuits and a combining circuit to ensure accurate extraction of detection pulses within specific thresholds, synchronizing with the clock pulse to prevent errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a one-shot multivibrator with resistor and capacitor elements is used for pulse height selection, then the circuit can be constructed with simple components, but the pulse width becomes unstable due to element characteristic variations
Solution Approach 1:
The patent replaces the analog RC timing circuit with a digital logic circuit synchronized to a crystal oscillator clock. This substitution eliminates dependence on resistor and capacitor characteristic variations, providing stable and precise pulse width control through digital counting mechanisms.
Solution Approach 2:
The patent changes the fundamental operating parameters from analog time constants (RC products) to digital clock cycles. By using a crystal oscillator to generate a stable clock signal and counting clock cycles to determine pulse width, the system achieves parameter stability independent of component tolerances.
2Ease of operation
If conventional delay circuits using logic IC response time are used, then the delay function can be achieved, but the delay time varies due to element variations
Solution Approach 1:
The patent replaces analog delay circuits based on logic IC propagation delays with a digital delay mechanism that counts clock cycles. This substitution provides precise and stable delay times determined by the number of clock cycles counted, independent of logic IC characteristic variations.
3Device complexity
If element characteristic variations are not compensated, then the circuit design remains simple, but count loss and measurement errors occur
Solution Approach 1:
The patent replaces the entire analog pulse processing chain with a digital system synchronized to a crystal oscillator. This substitution inherently compensates for element variations by using stable clock cycles as the timing reference, eliminating count loss and measurement errors without requiring complex compensation circuits.
Data Source
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AI summary
First and second pulse height detection circuits (3a, 3b) output pulse height detection signals which rise when a detection pulse obtained from a radiation detector (1) becomes greater than a lower threshold Lsh or an upper threshold Hsh, and fall when the detection pulse is smaller than the lower threshold Lsh or the upper threshold Hsh. Next, first and second rising and falling detection circuits (11a, 11b) detect rising and falling edges of the pulse height detection signals from the first and second pulse height detection circuits (3a, 3b) in synchronization with a clock pulse from a crystal oscillator (10), and a combining circuit (12) outputs a signal corresponding to the detection pulse that is within a range between the lower threshold Lsh and the upper threshold Hsh by combining both outputs from the first and second rising and falling detection circuits (11a, 11b), in synchronization with the clock pulse.