Current-Frequency Converter Switching for Wide-Range Measurement
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Solution Overview
Problem
Current switching elements in current/frequency converters, such as semiconductor-based switches and electromechanical switches, face limitations in leakage currents and switching frequency, restricting the dynamic range of measuring devices used for detecting ionizing radiation and other variables.
Innovation Solution
The combination of electronic and electromechanical switching elements, specifically a reed relay and a field effect transistor connected in series and parallel with an integration capacitor, controlled by a device that manages their operation based on the current strength, allowing high switching frequency and minimal leakage currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a purely electronic switching device is used in the discharge circuit, then switching speed is improved, but the device cannot handle high currents without damage
Solution Approach 1:
The patent combines a relay (mechanical switching device) and a semiconductor switching device (electronic switching device) in series within the discharge circuit. The relay handles high currents through its mechanical contacts designed for high current capacity, while the semiconductor switching device provides fast switching speed. This merging of two different switching technologies resolves the contradiction between switching speed and current handling capability.
2Strength
If a purely mechanical switching device is used in the discharge circuit, then current handling capability is improved, but switching speed deteriorates
Solution Approach 1:
The patent combines a relay (mechanical switching device) and a semiconductor switching device (electronic switching device) in series within the discharge circuit. The relay handles high currents through its mechanical contacts designed for high current capacity, while the semiconductor switching device provides fast switching speed. This merging of two different switching technologies resolves the contradiction between switching speed and current handling capability.
3Strength
If the relay and semiconductor switching device are connected in parallel, then current handling capability is improved, but contact erosion increases
Solution Approach 1:
The patent connects the relay and semiconductor switching device in series rather than parallel. This series connection ensures that the same current flows through both devices, allowing the relay to handle the high current while the semiconductor device provides fast switching. The relay contacts are designed to withstand the full current, and the semiconductor device protects against overcurrent conditions, thereby managing contact erosion through proper device selection and series configuration.
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 configuration extends the measuring range by several decades, ensuring high insulation resistance at low currents and negligible leakage at high currents, enabling reliable detection of varying measurement signals.
Implementation Method 1
an integrating capacitor (3a) which is charged with the measuring current (i) during a charging cycle
Implementation Method 2
a semiconductor switching device (5b), wherein the relay (5a) and the semiconductor switching device (5b) are connected in series
Data Source
Figure 1~3
AI summary
Measuring device for determining a measured quantity, comprising: - a sensor for generating a measuring current (i) dependent on the measured quantity, - a current/frequency converter (2) configured to generate a measuring signal (comp), in particular rectangular, whose frequency depends on the current intensity of the measuring current (i), wherein the current/frequency converter (2) comprises: - an integrating capacitor (3a) which is charged with the measuring current (i) during a charging cycle, and - a discharging circuit (5) configured to discharge the integrating capacitor (3a) during a discharging cycle as soon as the magnitude of a voltage appearing across the integrating capacitor (3a) exceeds a predetermined threshold value (Vth), - wherein the frequency of the measuring signal (comp) corresponds to the frequency at which charging and discharging cycles alternate, and - an evaluation unit (4) configured toto determine the measured quantity based on the frequency of the measurement signal (comp), - wherein the discharge circuit (5) comprises: - a relay (5a), - a semiconductor switching device (5b), - wherein the relay (5a) and the semiconductor switching device (5b) are connected in series and the series connection of relay (5a) and semiconductor switching device (5b) is connected in parallel to the integrating capacitor (3a), and - a control device (5c) configured to control the relay (5a) and the semiconductor switching device (5b) depending on the current of the measuring current (i).