Browse Prior Art Database

Method for Calibrating Probe Force

IP.com Disclosure Number: IPCOM000123228D
Original Publication Date: 1998-Jul-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 4 page(s) / 101K

Publishing Venue

IBM

Related People

Boyette Jr, JE: AUTHOR [+2]

Abstract

Disclosed is a device which provides a simple low cost method of determining probe force. The device uses a set of weights and a software sequenced procedure to relate drive current to probe pressure.

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This is the abbreviated version, containing approximately 52% of the total text.

Method for Calibrating Probe Force

   Disclosed is a device which provides a simple low cost
method of determining probe force.  The device uses a set of weights
and a software sequenced procedure to relate drive current to probe
pressure.

   A servo controlled voice coil actuator is used to move an
electrical probe into contact with a test point.  A means can also be
provided to drive a specific current through the motor such that a
desired force can be achieved.  There is a linear relationship
between the current running through a voice coil and the force
generated.  The amount of force generated for a given current can
fluctuate from system to system based on manufacturing variances in
the electronics and mechanics of the motor.  Although there is
variation, the linear relationship continues to apply and the
current-force relationship may be obtained by two sets of data points
(current-force pairs).  Additional points may be used for a least
squares fit.  The motor servo system is typically able to determine
current applied through the coil, and contact with an object, but a
separate means must be provided to establish the force developed.

   The mechanism disclosed provides a simple low cost method
in which to measure the force developed by the voice coil motor.  The
diagrams show two such mechanisms.  Each mechanism is based on
providing a known set of weights such that the force required to move
the captive weight is known.  The first mechanism, shown in figure
one, is used by motors which probe from below thus opposing gravity.
The transfer pin is provided so that a calibrated bottom probe may
transfer a calibrated force to the upper probes which actuate in the
direction of gravity.  The second mechanism, shown in figure two,
provides the calibrated weight to upper probes which actuate in the
direction of gravity when a bottom probe is unavailable.

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