Balanced Embedded Contact Sensor for HDD Noise Cancellation
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Solution Overview
Problem
Existing hard-disk drive (HDD) systems face challenges in accurately detecting physical contact between the read/write head and the magnetic-recording disk due to noise interference in resistor temperature detector (RTD) architectures, leading to unsatisfactory measurement precision.
Innovation Solution
A balanced embedded contact sensor (bECS) is implemented using a resistive temperature detector (RTD) within a head slider, integrated into a bridge circuit with a balanced resistor, which cancels out noise and allows for precise temperature measurements, enabling accurate detection of physical contact between the head slider and the magnetic-recording disk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single RTD architecture is used to detect physical contact, then the device complexity is low, but the measurement precision deteriorates due to noise interference
Solution Approach 1:
The single RTD sensor is segmented into two separate RTD sensors (RTD1 and RTD2) positioned at different locations on the slider. This segmentation allows the system to differentiate between noise signals and actual contact signals by comparing temperature readings from multiple positions, thereby improving measurement precision while managing device complexity through distributed sensing.
Solution Approach 2:
A differential measurement approach is introduced as an intermediary processing method. The system calculates the temperature difference between RTD1 and RTD2 to eliminate common-mode noise signals. This intermediary calculation layer filters out environmental noise while preserving actual contact temperature changes, improving measurement precision without significantly increasing overall system complexity.
2Reliability
If a single RTD architecture is used, then the device complexity is low, but the reliability deteriorates due to noise affecting accurate detection
Solution Approach 1:
The reliability is improved by segmenting the single-point measurement into multi-point measurements using RTD1 and RTD2. By monitoring temperature at multiple locations, the system can reliably distinguish between random noise fluctuations and genuine contact events, enhancing detection reliability while keeping the sensor architecture relatively simple through the use of identical sensor components.
Solution Approach 2:
A feedback mechanism is implemented where the temperature difference signal from the two RTDs is continuously monitored and processed. When the temperature difference exceeds a predetermined threshold, the system generates a contact detection signal. This feedback loop ensures reliable contact detection by dynamically responding to actual thermal changes while filtering out noise through threshold-based decision making.
3Adaptability or versatility
If environmental changes occur, then the RTD resistance changes, but recalibration is required which increases loss of time
Solution Approach 1:
The environmental influence is extracted and isolated through differential measurement. By calculating the temperature difference between RTD1 and RTD2, the system removes common-mode environmental effects such as ambient temperature changes, pressure variations, and humidity effects. This extraction of environmental noise allows the system to maintain accuracy across different environments without requiring recalibration, improving adaptability while avoiding time loss.
Solution Approach 2:
The system exploits the asymmetric response of the two RTDs to different types of changes. Environmental changes affect both RTDs equally (symmetric effect), while actual contact affects only one RTD (asymmetric effect). By taking the difference between the two readings, the system asymmetrically filters out environmental influences while preserving contact detection capability, enabling environmental adaptability without recalibration.
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
The bECS achieves greater precision in detecting physical contact and maintains resistance balance across environmental changes, reducing the need for recalibration due to changes in altitude, pressure, temperature, or humidity.
Implementation Method 1
A balanced embedded contact sensor (bECS) may be implemented by a resistive temperature detector (RTD) that is comprised within a head slider
Implementation Method 2
The bridge circuit of an embodiment allows the affect of noise generated at the head slider to be cancelled at the read/write integrated circuit (IC)
Data Source
AI summary
Approaches for a hard-disk drive (HDD) having a balanced resistive temperature detector (RTD). A HDD includes a head slider comprising a single RTD. A read/write IC comprises a balance resistor having the same resistance as the single RTD when the head slider is not in physical contact with the disk. The same amount of current flows through the single RTD and the balance resistor except when the head slider is in physical contact with the disk. Detecting a voltage change across the single RTD enables physical contact between the head slider and the disk to be accurately detected using a circuit with low noise. Alternately, the head slider may include two RTDs connected in sequence, and the balance resistor may possess the same resistance as the two RTDs. The two RTDs may vary inversely with environmental changes to avoid the need to recalibrate the balance resistor after any environmental change.