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NK Biotechnical Corporation

 10850 Old County Road 15
Minneapolis, MN 55441

1-763-541-0411

Toll Free, US Only:
1-800-462-3751

 

neb-at-nkb.com

TRIBOSENZ EDS System

Tribology is the study of stiction force on a hard disk.

Accurate characterization of the interface between the head and disk in terms of head-disk separation and head-disk frictional interaction is crucial to understanding and improving its tribology and durability. NKB offers a state-of-the-art slider/rigid disk interface using a friction transducer (Tribosenz Transducer) which utilizes a feedback concept, offers much higher sensitivity and bandwidth for interface friction measurements than the conventional transducers based on strain gage elements

The TRIBOSENZ EDS System was conceptually designed and prototyped by IBM's Thomas J. Watson Research Center, Yorktown, NY.

NK Biotechnical Corporation, in cooperation with IBM Storage Systems Division, Rochester, MN, completed the development and testing of this system, including addition of NKB proprietary concepts for "adaptive loop stabilization".

The result of these joint research and development efforts is a fully operational TRIBOSENZ EDS System, capable of accurate, reliable, and repeatable measurements. These systems have been in use at IBM facilities since 1991 SYSTEM DESCRIPTION

The components of the TRIBOSENZ EDS System are:

  • The 2 channel EDS amplifier
  • Two EDS transducers
  • A calibrator

The EDS Amplifier 

The TRIBOSENZ 2 channel amplifier was designed to measure static and dynamic friction forces along a single axis. Signal conditioning consists of: a) establishing the collector voltage on the detector; b) converting the photocurrent to a voltage; c) offsetting the resulting voltage in accordance with the mechanical zero position of the EDS transducer; and d) PID filtering of the signal.

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EDS Transducers 

The TRIBOSENZ EDS Transducers are provided in matched sets, consisting of the transducer, a cable, a locking pin, and a dedicated amplifier channel. The optical position sensor is an infrared source and detector in a single package. The detector is a open collector photo-transistor. The emitter is an LED.

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Calibrator 

The TRIBOSENZ calibrator is designed to enable calibration of the EDS Transducer utilizing either a pulley arrangement or gravitational loads. Provision has been made for changing the load vector +/-10 degrees in either pulley or gravitational configurations. 

A set of weights, traceable to NIST, is provided with the calibrator.

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System Applications
 

Hard Disks

  • Startup friction
  • Take off velocity
  • Aerodynamic drag
  • Liquid contact recording property
  • Tribology of miniature sliders
  • Spindle motor reactive torque
  • Force vs. position in static magnets

Medical and Biological Sciences

  • "twitching" force reflexes

Aerospace

  • Aerodynamic friction
  • Torque
  • Turbulence
SYSTEM COMPARISONS TRIBOSENZ vs. Strain gage Transducers Below are typical traces of Strain Gage Transducers vs. a TRIBOSENZ Transducer in measuring dynamic stiction force on a hard disk {short description of image} Observe the damped transient motion with the TRIBOSENZ vs. the "ringing" in the output of the strain gage transducers 
VENDOR COMPARISON Take off condition of two sliders {short description of image} Observe that vendor no. 2's slider drags on for about 50% longer than vendor no. 1. 
 

SYSTEM SPECIFICATIONS
STATIC measurement bandwidth is Dc - 10 Hz
Range of Force, Full Scale +/- 10,20,40 grams
Linearity +/- 0.20% F.S.
Hysteresis +/- 0.25% F.S.
Zero Shift +/- 0.10% F.S.
Long term stability +/- 15 milligrams
Resolution at 10 grams F.S. +/- 0.5 milligrams
Resolution at 20 grams F.S. +/- 1 milligram
Resolution at 40 grams F.S. +/- 2 milligrams
Temperature effect on zero 18-35 C, 0.011%/C/F.S.:65-95 F, 0.005%/F/FS. 
DYNAMIC
Bandwidth, (PID mode on rotating disk, measured by noise injection 600 Hz (-3 dB)
Noise (Measurement bandwidth is 0.2 Hz to 1 kHz at - 3 dB)
          at 10 grams F.S. 8.7 mV RMS (0.09% F.S.), 69 mV P-P (0.35%F.S.)
          at 20 grams F.S. 4.3 mV RMS (0.04% F.S.), 35 mV P-P (0.18%F.S.)
          at 40 grams F.S. 2.2 mV RMS (0.02 % F.S.), 17 mV P-P (0.09%F.S.)
Equivalent Force +/- 9 mg RMS, +/- 68 mg P-P

The noise specifications are consistent with the static resolution specifications due to the fact that the spectral density of the noise below 200 Hz is approximately 20uV RMS per root Hz. In a 10 Hz bandwidth, this amounts to 63uV RMS (20 gram range). Thus the noise contribution to the static errors is about +/- 0.12 milligram is the 20 g range.