Computational and Experimental Investigation of Contact Detect Response of a Head-Integrated Thermistor on HAMR vs. PMR Media

The migration from perpendicular magnetic recording (PMR) to heat-assisted magnetic recording (HAMR) in the hard disc drive (HDD) industry brings unique challenges for head-disc contact detection (CD) and with precisely setting head-disc clearance. In this study we provide numerical model calculations of a head-integrated thermistor’s electric resistance as a function of head-disc clearance and compare the modeled results with measurements of thermistor resistance for heads flying over PMR and HAMR media. Such comparisons serve to assess the accuracy of the modeling techniques and to understand the impact that the media type plays in CD capability of the head-integrated thermistor.

Study of Contact Detect Response for PMR and HAMR Media Using the Integrated Thermistor Based Proximity Sensor

As the Hard Disk Drive industry migrates from PMR to HAMR technology, it is important to understand differences in the measurement of contact detection between PMR vs. HAMR media. Compared to PMR media, HAMR media tends to be rougher and has a higher thermal conductance. Since some contact detection methods rely on interface heat transfer, it is important to understand the impact of media type on measurements. In the current paper, we present results from mechanical spinstand studies using the integrated thermistor in the head. The heater in the head is dithered at a fixed frequency and the thermistor response is analyzed at that frequency. Changes in the thermistor resistance as a function of head-media clearance are used to understand how thermal conduction differences between PMR vs. HAMR media may impact contact detection. We find that heat conduction is different between HAMR and PMR media types and can have an impact on contact detection.

Design of Temperature Detection Alarm Circuit Based on Multisim

This paper mainly describes the characteristics of the utilization of thermistor resistance changes with temperature. When temperature is too low or too high, the thermal resistance values change correspondingly. This causes its associating sensor voltage signal changes. The changes of the voltage signal will lead to the subtraction proportional operation and dual comparator threshold voltage change correspondingly. This appearance enables the double threshold voltage comparators output highly, so that the multivibrator starts emitting diode conduct. Therefore the alarm circuit works.

Alternative conifer release treatments affect below- and near-ground microclimate

Li-Cor weather stations and thermistor/resistance soil cells were used during 1994 to monitor microclimate in young spruce plantations during the first growing season after the following replicated alternative conifer release treatments [brush saw, Silvana Selective, Release® (a.i., triclopyr) herbicide. Vision® (a.i., glyphosate) herbicide], and control (no treatment) were applied. Treatments were conducted in mid-August (herbicides) and late October and early November (cutting) 1993. In 1994, temperature, photosynthetically-active radiation (PAR), and relative humidity (RH) were monitored near (0.25 m) and above (2 m) the forest floor. Fiberglass thermistor/resistance soils cells were installed 15 and 30 cm deep, and soil moisture and temperature were read bimonthly. In relation to controls, PAR near and above the forest floor increased on all conifer release treatments. By July, PAR near the forest floor declined on both the cut and herbicide treatments. That decline occurred in early July for the brush saw treatment, but in late July for the Vision® treatment. PAR at 2 m was similar among conifer release alternatives and significantly greater than for controls throughout the growing season. Increased solar radiation resulted in significant soil warming following the conifer release treatments. During the growing season, duff (5 cm) and mineral (15 cm) soil temperatures were highest for the Vision® and Release® treatments, and lower on the brush saw and control treatments. November soil temperatures were slightly cooler in released than control plots. Frequent rains resulted in relatively high RH and soil moisture readings during the 1994 growing season. Relative humidity near the forest floor was lowest for the Vision®, intermediate for the brush saw, and highest for the control treatments. During the growing season after treatments, soil moisture levels were higher on treated than control plots. Key words: microclimate, alternative conifer release treatments, Fallingsnow Ecosystem Project, photosynthetically-active radiation (PAR), soil temperature and moisture, relative humidity, ecosystem study