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Detection Circuit for Pressure Sensitive Contact Probe

IP.com Disclosure Number: IPCOM000080024D
Original Publication Date: 1973-Oct-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 3 page(s) / 37K

Publishing Venue

IBM

Related People

Barr, ER: AUTHOR [+2]

Abstract

Contact probe 10 has mounted thereon a proximity detector 12 for sensing when the probe is deflected. Typically, this would be accomplished by an RF sensing coil mounted on a probe spindle to detect when the probe deflects, as a result of making contact with the test part, not shown.

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Detection Circuit for Pressure Sensitive Contact Probe

Contact probe 10 has mounted thereon a proximity detector 12 for sensing when the probe is deflected. Typically, this would be accomplished by an RF sensing coil mounted on a probe spindle to detect when the probe deflects, as a result of making contact with the test part, not shown.

To drive the proximity detector 12, a current source 14 is provided. In an environment where the probe 10 would be mounted on a rotary spindle, a slip ring 16 and a brush 18 are required to transmit the electrical energy from the current source 14 to the proximity detector 12.

The proximity detector 12 is of the impedance varying type. Therefore, when the proximity detector detects the probe has deflected, its impedance will change changing the voltage Vs across the constant-current source 14. The voltage Vs across the current source is monitored to detect probe contact.

Variable resistance 20 is used to adjust the current source 14 to the optimum operating point of the proximity detector 12. This simplifies the procedure for changing probes, because mounting a new probe may change the optimum operating point of the proximity detector.

The voltage Vs is amplified by amplifier 22 and passed on to circuitry that detects changes in Vs, and thus indicates that probe 10 has deflected. The amplified Vs is first applied to a DC level indicator 24. Indicator 24 is a meter to assist in the adjustment of current source 14 by resistor 20, as described above.

The signal is also amplified by isolation amplifier 26 and passed to both input legs of a differential amplifier (diff amp) 28. The positive leg of diff amp 28 contains capacitor 30, while the negative leg of diff amp 28 con...