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Detection of Air Bearing Collapse using Peak Sample and Hold Comparator Circuit

IP.com Disclosure Number: IPCOM000103094D
Original Publication Date: 1990-Jun-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 2 page(s) / 79K

Publishing Venue

IBM

Related People

Acciai, MA: AUTHOR [+2]

Abstract

The drilling of holes for which precision controlled depth is essential can be accomplished if the top surface of the work piece is known in relation to the drill bit tip. One method of ascertaining this relationship is to utilize a hall effect sensor to detect the collapse of the air bearing on the drill machine, as described in the reference noted below. A described circuit provides the capacity to track and compare a varying input peak with relative immunity to component degradation because the reference threshold is taken from the static input peak. The circuit allows for a change in peak detection over a wide frequency range to accommodate variations in spindle RPM. The circuit works in the following manner.

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Detection of Air Bearing Collapse using Peak Sample and Hold Comparator Circuit

      The drilling of holes for which precision controlled depth is
essential can be accomplished if the top surface of the work piece is
known in relation to the drill bit tip.  One method of ascertaining
this relationship is to utilize a hall effect sensor to detect the
collapse of the air bearing on the drill machine, as described in the
reference noted below.  A described circuit provides the capacity to
track and compare a varying input peak with relative immunity to
component degradation because the reference threshold is taken from
the static input peak.  The circuit allows for a change in peak
detection over a wide frequency range to accommodate variations in
spindle RPM.  The circuit works in the following manner.

      The output generated by the hall effect sensor is used to drive
two analog level hold detectors A, B in parallel, as shown in the
schematic (Fig. 1).  The detectors in turn provide a level to a
comparator that sets an edge-triggered transistor-to- transistor
latch.  The use of junction gate field-effect transistor (J-FET)
amps, diodes with feedback and polystyrene capacitors allow for quick
level detection with a minimum of droop when sampling during the
drill dip cycle.

      When the turbine is running free bore during a down stroke a
microprocessor removes the reset line and the level of the input
signal 1 (Fig. 2) is set by the level/hold portion...