Sensor Calibration Device Using Resistor Network
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Solution Overview
Problem
Conventional calibration processes for conductivity sensors in aqueous solutions face challenges such as variable conductivity solution, temperature fluctuations, and inconsistencies between third-party probes, leading to low calibration pass rates.
Innovation Solution
A calibration device and method that apply a controlled voltage across sensor electrodes with a resistor network to replicate the properties of an electrochemical calibration solution, eliminating the need for direct solution contact and simulating a 25-degree-Celsius environment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional calibration processes use electrochemical calibration solutions, then the sensor can be calibrated, but the conductivity solution becomes highly variable and fluctuates after refreshing between sets
Solution Approach 1:
The patent creates an electrical copy of the calibration solution's properties by using a resistor network that replicates the conductivity characteristics. Instead of using physical electrochemical solutions that fluctuate, the invention uses equivalent electrical resistance values (e.g., 40.2 ohms for 12.88 mS/cm calibration) to simulate the solution's electrical properties, eliminating variability while maintaining calibration accuracy
Solution Approach 2:
The patent replaces the chemical/electrochemical system (calibration solutions with ions) with an electrical system (resistor networks). This substitution eliminates the need for physical solutions that can fluctuate, contaminate, or degrade, while maintaining the essential electrical conductivity measurement function through pure electrical components
2Measurement precision
If conventional calibration processes maintain constant solution temperature, then calibration accuracy improves, but temperature fluctuations occur when adjusting water bath temperature
Solution Approach 1:
The patent creates an electrical copy of the temperature-compensated conductivity signal. The resistor network is designed to simulate not only the conductivity value but also the temperature response characteristics, allowing the calibration to proceed without actual temperature control while achieving the same measurement accuracy as if temperature were perfectly stabilized
Solution Approach 2:
The patent extracts the essential calibration function from the temperature-controlled solution environment. By removing the need for physical solutions and temperature control apparatus, the invention isolates and maintains only the critical electrical conductivity measurement aspect, eliminating temperature-related variability entirely
3Ease of manufacture
If third-party conductivity and temperature probes are used for reference calibration, then calibration can be performed, but the probes do not agree with one another for temperature or conductivity readings
Solution Approach 1:
The patent makes the calibration system self-referential by using precision resistor networks with known, stable resistance values as the reference standard. Instead of relying on external third-party probes that may drift or disagree, the system uses internally defined electrical standards (e.g., 40.2 ohms representing 12.88 mS/cm) that do not require external calibration or agreement with other probes
Solution Approach 2:
The patent replaces mechanical/probe-based reference measurements with electrical reference standards. The resistor network provides a stable, reproducible electrical reference that eliminates the need for physical contact probes, thereby avoiding the variability and disagreement inherent in third-party probe measurements
4Measurement precision
If NIST-certified conductivity solution is used for calibration, then calibration accuracy is ensured, but the solution must be unused and thoroughly cleaned after calibration, increasing cost and manufacturing time
Solution Approach 1:
The patent creates an electrical replica of the NIST-certified solution's conductivity properties using resistor networks. This copy eliminates the need for physical consumption and disposal of certified solutions, allowing unlimited reuse of the electrical calibration standard without contamination concerns, thereby dramatically increasing throughput while maintaining accuracy
Solution Approach 2:
The patent replaces expensive, consumable NIST-certified solutions with inexpensive, reusable electrical resistor networks. The resistor-based calibration standard can be used indefinitely without degradation, contamination, or disposal requirements, eliminating the recurring cost and time associated with purchasing and cleaning physical calibration solutions
5Measurement precision
If stability time is allowed for sensor body and conductivity solution to reach required temperature, then calibration accuracy improves, but operator monitoring is required constantly
Solution Approach 1:
The patent creates an electrical copy of the temperature-stabilized calibration condition. The resistor network is designed to provide the correct electrical resistance value regardless of temperature fluctuations, effectively copying the ideal calibration state without requiring actual thermal equilibrium, thereby eliminating the need for operator monitoring of temperature stability
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 solution enables a more controlled and repeatable calibration process, improving the accuracy and consistency of conductivity sensor calibration, and increasing the calibration pass rate.
Implementation Method 1
A first resistor is connected between the at least two sensor electrodes and coupled to the first connector. The resistor has a value such that a current flow between the at least two sensor electrodes replicates the properties of an electrochemical calibration solution.
Data Source
AI summary
A calibration device for a conductivity sensor for aqueous solutions. The calibration device includes a first connector configured to electrically couple with the sensor electrodes of the conductivity sensor. The connector is further configured to provide for the application of a controlled voltage across at least two of the sensor electrodes. A first resistor is connected between the at least two sensor electrodes and coupled to the first connector. The resistor has a value such that a current flow between the at least two sensor electrodes replicates the properties of an electrochemical calibration solution. In certain embodiments, the calibration device is configured for pH sensors or dissolved oxygen sensors.