Conductivity Sensor Self-Diagnostics Using Electrical Range Detection
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Solution Overview
Problem
Conductive conductivity sensors cannot detect electrode malfunctions or determine if they are outside the measurement medium or if the electrode line is interrupted, making it difficult to ensure the sensor's functionality.
Innovation Solution
A method involving the application of a first electrical variable to the electrodes and measuring a second electrical variable to determine if a malfunction is present, by dividing the measuring range into three ranges to differentiate between the sensor being in the medium, outside the medium, or having an electrode break, using variables such as electrical current, impedance, or capacitance, and employing a microcontroller for analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional conductivity sensors are used without additional detection mechanisms, then the device complexity remains low, but the reliability of sensor functionality cannot be ensured
Solution Approach 1:
The existing conductivity sensor electrodes are made to serve dual purposes: their primary function for conductivity measurement and a secondary function for self-diagnostics. By applying test voltages to the same electrodes and analyzing the resulting currents, the system can detect electrode breaks, air exposure, and other malfunctions without adding separate detection electrodes or components.
Solution Approach 2:
The conductivity sensor performs self-diagnostics by using its own electrodes and measurement circuitry to detect its own malfunction states. The evaluation unit analyzes current measurements taken during normal operation to identify conditions such as electrode breaks or air exposure, enabling the sensor to self-monitor its functionality without external diagnostic equipment.
2Measurement precision
If the measuring range is divided into multiple ranges for malfunction detection, then the measurement precision for detecting electrode states improves, but the device complexity increases due to additional evaluation requirements
Solution Approach 1:
The evaluation unit detects electrode states by monitoring changes in electrical current parameters under different test conditions. By applying test voltages and measuring the resulting currents, the system identifies distinct current ranges that correspond to different electrode states (normal operation, air exposure, electrode break), enabling precise state detection through parameter analysis.
Solution Approach 2:
The system performs preliminary diagnostic measurements by applying test voltages to the electrodes before or during normal conductivity measurement operations. This preliminary action allows the evaluation unit to assess electrode functionality and detect malfunctions proactively, ensuring reliable measurements are only performed when electrodes are in proper condition.
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 reliable detection of electrode states, distinguishing between functional, partially outside, and malfunctioning conditions, allowing for improved sensor functionality assessment and ensuring accurate conductivity measurements.
Implementation Method 1
the electrodes form with an electrical circuit an oscillatory circuit, and frequency is used as the second electrical variable
Implementation Method 2
used as the second electrical variable is the capacitance between the electrodes
Data Source
AI summary
A method and a sensor for ascertaining at least one malfunction of a conductive conductivity sensor having at least two electrodes applying a first electrical variable to the electrodes measuring at least a second electrical variable on the electrodes and deciding whether a malfunction is present based on measuring the second electrical variable. The second electrical variable is located in a first range when measuring the medium when no malfunction is present, and the second electrical variable is located in a second range in the case of a first malfunction, especially when the conductivity sensor is located at least partially outside of the medium, and the second electrical variable is located in a third range when a second malfunction is present, especially an electrode break or a break in a line to the electrodes.