Humidity Sensor Abnormality Detection via Timing-Based Voltage Measurement
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Solution Overview
Problem
Existing humidity sensor systems in image forming apparatuses face challenges in accurately detecting humidity levels, particularly at low humidity ranges and in high humidity environments, due to exponential impedance changes, leading to difficulties in distinguishing between sensor failures and actual humidity conditions, which results in erroneous image forming conditions.
Innovation Solution
A humidity detecting apparatus with a humidity detecting element and a resistor, where a clock signal is output to the element and resistor, and the voltage at specific timing is measured to differentiate between normal and abnormal conditions, allowing for accurate detection of humidity and sensor integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an impedance change type humidity sensor element is used to monitor the using environment, then the humidity can be detected, but it becomes difficult to distinguish between sensor failures and actual humidity conditions, leading to measurement errors
Solution Approach 1:
The patent applies preliminary action by performing a sensor status check before actual humidity measurement. The microcontroller first outputs a test clock signal and measures the voltage at the connecting point to determine if the sensor is functioning normally. Only after confirming the sensor is operational does the system proceed to measure actual humidity levels. This preliminary verification prevents erroneous measurements caused by sensor failures.
Solution Approach 2:
The patent introduces an intermediary measurement approach by measuring voltage at the connecting point between the humidity sensor and resistor. This voltage measurement serves as an intermediary indicator to assess sensor health status. By monitoring this intermediate voltage signal, the system can detect sensor abnormalities without directly measuring humidity, thereby distinguishing between sensor failures and actual humidity conditions.
2Device complexity
If the voltage is measured at a single predetermined timing, then the circuit construction is simple, but it is impossible to detect sensor abnormalities or distinguish between sensor failures and actual humidity conditions
Solution Approach 1:
The patent applies preliminary action by performing a sensor status check before actual humidity measurement. The microcontroller first outputs a test clock signal and measures the voltage at the connecting point to determine if the sensor is functioning normally. Only after confirming the sensor is operational does the system proceed to measure actual humidity levels. This preliminary verification prevents erroneous measurements caused by sensor failures.
Solution Approach 2:
The patent implements periodic action by using a clock signal with a predetermined frequency to periodically drive the humidity sensor. The microcontroller measures the voltage at specific timing intervals (rising edge or falling edge of the clock signal) to monitor sensor status. This periodic measurement approach enables both simple circuit operation and accurate sensor status detection through timing-based discrimination.
3Measurement precision
If the humidity sensor operates in high humidity environments, then it can monitor the using environment accurately, but the exponential impedance change makes it difficult to distinguish between sensor failures and actual high humidity conditions
Solution Approach 1:
The patent applies preliminary action by performing a sensor status check before actual humidity measurement. The microcontroller first outputs a test clock signal and measures the voltage at the connecting point to determine if the sensor is functioning normally. Only after confirming the sensor is operational does the system proceed to measure actual humidity levels. This preliminary verification prevents erroneous measurements caused by sensor failures.
Solution Approach 2:
The patent implements feedback by continuously monitoring the voltage at the connecting point between the humidity sensor and resistor. The microcontroller uses this voltage feedback to determine both sensor operational status and actual humidity levels. The system adjusts its operation based on this feedback, switching between test mode and measurement mode according to the sensor's actual state, thereby accurately detecting both sensor failures and high humidity conditions.
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 continuous high-quality image production by accurately detecting humidity and sensor abnormalities, reducing errors in image forming conditions and improving the dynamic range of humidity detection.
Implementation Method 1
a humidity sensor element using such a phenomenon that an impedance changes due to an adsorption of water molecular is known
Implementation Method 2
The resistance change type humidity sensor element has a high resistance on the low humidity side and its resistance value exponentially decreases (RH-C characteristics become almost linear) according to the increase in humidity
Data Source
AI summary
A humidity measuring apparatus including: a humidity detecting element whose resistance value changes according to a humidity change; a resistor serially connected to the humidity detecting element; a signal output unit which outputs a clock signal to the humidity detecting element and the resistor; and a measuring unit which detects a voltage of a connecting point of the humidity detecting element and the resistor at predetermined timing from an edge of the clock signal and obtains a humidity based on the detected voltage, wherein an abnormality of the humidity detecting element is detected by detecting the voltage at timing different from the predetermined timing based on the voltage detected by the measuring unit.