Browse Prior Art Database

Proximity Sensor Using a Single Piezoceramic Ultrasonic Transducer

IP.com Disclosure Number: IPCOM000061357D
Original Publication Date: 1986-Jul-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 29K

Publishing Venue

IBM

Related People

Rohrer, GD: AUTHOR [+3]

Abstract

For the detection of an object, certain products employ a matched pair of piezoceramic ultrasonic transducers with the ceramic crystal and the mechanical housing resonance frequency being set to the oscillating frequency. One disadvantage of such an arrangement is that as a result of aging or temperature changes, the crystal's resonance frequency drifts out of the allowed bandwidth. This article discloses the use of a single piezoceramic ultrasonic transducer for the detection of an object along with a circuit to automatically compensate for any change in the crystal's resonance frequency as a result of age or temperature change. In the figure there is shown a piezoceramic device 1, operating at or near its natural resonance frequency, which is driven by the voltage-controlled oscillator 2.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 78% of the total text.

Page 1 of 2

Proximity Sensor Using a Single Piezoceramic Ultrasonic Transducer

For the detection of an object, certain products employ a matched pair of piezoceramic ultrasonic transducers with the ceramic crystal and the mechanical housing resonance frequency being set to the oscillating frequency. One disadvantage of such an arrangement is that as a result of aging or temperature changes, the crystal's resonance frequency drifts out of the allowed bandwidth. This article discloses the use of a single piezoceramic ultrasonic transducer for the detection of an object along with a circuit to automatically compensate for any change in the crystal's resonance frequency as a result of age or temperature change. In the figure there is shown a piezoceramic device 1, operating at or near its natural resonance frequency, which is driven by the voltage-controlled oscillator 2. A standing wave, which is shown by the distance "d", is set up and amplified by the passive vibrating plate 3. The current sense circuit 4 is used to detect the amount of current to drive the crystal 1. The output of the sense circuit 4 is supplied to the storage device 5 and compared to the present value of the resonance frequency with comparator 6. As the standing wave is interrupted by an object moving in front of the crystal 1, a drastic change in current, from the current sense circuit 4, will occur causing comparator 6 to change output states. Besides sensing immediate changes, the current sense circuit 4...