Alternating-Bias RTD Detection for HDD Defect Scanning
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Solution Overview
Problem
Current resistance detection architectures in hard disk drives (HDDs) are limited to single path monitoring, requiring time-consuming switching between alternating current (AC) and direct current (DC) modes for defect scanning and fly-height monitoring, respectively, which increases testing time significantly.
Innovation Solution
A dual path monitoring resistance detection architecture that supports continuous operation in both AC and DC modes using an alternating-bias signal with a specific clock frequency to modulate and demodulate signals, allowing for simultaneous detection of resistance values and changes in real-time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If single path monitoring architecture is used, then device complexity is reduced, but productivity deteriorates due to time-consuming switching between AC and DC modes
Solution Approach 1:
The patent divides the monitoring function into two separate paths: an AC mode path for defect scanning and a DC mode path for fly-height monitoring. Each path operates independently and continuously, eliminating the need to switch between modes. The AC path includes AC coupling capacitors and AC amplifiers, while the DC path includes DC coupling resistors and DC amplifiers, allowing simultaneous operation of both modes without interference.
Solution Approach 2:
The patent combines both AC and DC monitoring paths within a single resistance detection architecture, allowing the system to perform both defect scanning and fly-height monitoring simultaneously. The combined architecture shares common components such as the RTD sensor and signal processing units while maintaining separate signal paths to preserve the advantages of both AC and DC modes.
2Adaptability or versatility
If switching between AC and DC modes is implemented, then adaptability is improved, but loss of time increases due to mode switching requirements
Solution Approach 1:
The patent enables continuous operation in both AC and DC modes simultaneously through dual path monitoring. The AC path continuously scans for defects while the DC path continuously monitors fly-height, eliminating idle time during mode transitions. Both paths operate in parallel, ensuring that useful detection actions are always ongoing without interruption or switching delays.
3Measurement precision
If resistance detection is performed, then measurement precision is improved, but object-generated harmful factors increase due to noise interference
Solution Approach 1:
The patent extracts and separates the noise components from the resistance detection signal using AC coupling. By blocking DC offsets and low-frequency noise through capacitors, the system extracts only the relevant AC signal components containing defect information. The DC path simultaneously extracts the steady-state resistance value free from AC noise, achieving noise-free measurements for both modes.
Solution Approach 2:
The patent introduces AC coupling capacitors as intermediary elements between the RTD sensor and amplifiers. These capacitors act as mediators that block DC noise and low-frequency interference while allowing the AC defect detection signal to pass through. This intermediary component protects the sensitive amplification stages from noise contamination.
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 approach reduces testing time by up to several hours, enabling more efficient defect scanning and fly-height monitoring, and effectively mitigates noise interference through signal modulation and filtering.
Implementation Method 1
modulate an input signal of the first amplifier circuit using the first clock frequency to generate a modulated signal
Implementation Method 2
demodulate, at an output of a second amplifier, an amplified modulated signal using the first clock frequency to generate a resistance detection signal
Implementation Method 3
amplify the modulated signal
Data Source
AI summary
Various illustrative aspects are directed to a data storage device comprising a slider with a resistive temperature detector (RTD) having a first resistance electrically connected to a first amplifier and a plurality of controlled current sources and switches, and one or more processing devices configured to: control the switches to generate an alternating-bias signal having a first clock frequency for biasing the first resistance, modulate an input signal of the first amplifier using the first clock frequency to generate a modulated signal, demodulate an amplified modulated signal at an output of a second amplifier using the first clock frequency to generate a resistance detection signal, the second amplifier coupled to the first amplifier, and process the resistance detection signal to determine the first resistance and/or a change in value of the first resistance.