Browse Prior Art Database

Probe Multiplexing using Pneumatically Controlled Probes

IP.com Disclosure Number: IPCOM000114043D
Original Publication Date: 1994-Nov-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 78K

Publishing Venue

IBM

Related People

Bickerton, T: AUTHOR [+4]

Abstract

This disclosure describes how pneumatically controlled probes are used to multiplex high impedance probes, achieving both a reduction in the amount of conventional switching equipment needed, and reducing the load on the circuit under test when that circuit is not being selected for measurement.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Probe Multiplexing using Pneumatically Controlled Probes

      This disclosure describes how pneumatically controlled probes
are used to multiplex high impedance probes, achieving both a
reduction in the amount of conventional switching equipment needed,
and reducing the load on the circuit under test when that circuit is
not being selected for measurement.

      The diagram shows the interconnection between eight sets of
measurements to be made, and how the air probes (pneumatically
controlled probes) and electrical signals interact.

      Conventional spring loaded probes are mounted in a fixture in a
pattern that matches electrical test points in a printed circuit
board to be tested.  When a circuit board is loaded on to the spring
loaded probe, it pushes the spring down, and the spring forces the
pin against the board with increasing pressure.  This makes
electrical contact.  Another wire on the end of the probe or probe
socket connects the probe to test equipment, usually to a switch
matrix or multiplexer, and finally to the actual device that performs
the measurement.

      A pneumatically controlled probe is a probe and air cylinder
built into the same device.  When air pressure is connected and
applied, the pressure forces the tip of the spring loaded probe out.
The spring disengages the probe from the circuit under test when the
air is released.

      The Figure below shows how to connect the air probes to eight
different points in a circuit to be measured.  These points are
illustrated here by eight diodes CR1 through CR8.

      If standard spring loaded probes were used, an eight way DPST
switch would be needed to select one of the eight signals.

      Using the solenoid actuated air valves and pneumatically
controlled probes, the amount of switching can be reduced.

      In the Figure, there are four pneumatic controls needed,
labelled AIR 'A' through AIR 'D'.  The number of signal switches
needed is reduced to two DPST switches.

    ...