Browse Prior Art Database

Ultrasonic Doppler Vibrometer

IP.com Disclosure Number: IPCOM000062459D
Original Publication Date: 1986-Nov-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 55K

Publishing Venue

IBM

Related People

Imaino, W: AUTHOR [+2]

Abstract

We have developed a rugged, inexpensive device that allows non-contact, inherently quantitative measurement of vibrations. The probe is insensitive to position, since it detects the frequency shift of the ultrasound due to the vibration of the surface. The constraint on the optical preparation of the surface is much relaxed, as compared to optical measurements, since the wavelength of the ultrasound in our device is about 2 mm. The use of the Doppler effect to detect the motion of objects is not uncommon, as evidenced by Doppler radar to detect the speed of moving vehicles and laser Doppler vibrometers and velocimeters. However, the use of ultrasound rather than electromagnetic radiation to detect motion on the order of 100 nanometers is a unique demonstration. Fig. 1 shows a schematic diagram of the experimental arrangement.

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 52% of the total text.

Page 1 of 2

Ultrasonic Doppler Vibrometer

We have developed a rugged, inexpensive device that allows non-contact, inherently quantitative measurement of vibrations. The probe is insensitive to position, since it detects the frequency shift of the ultrasound due to the vibration of the surface. The constraint on the optical preparation of the surface is much relaxed, as compared to optical measurements, since the wavelength of the ultrasound in our device is about 2 mm. The use of the Doppler effect to detect the motion of objects is not uncommon, as evidenced by Doppler radar to detect the speed of moving vehicles and laser Doppler vibrometers and velocimeters. However, the use of ultrasound rather than electromagnetic radiation to detect motion on the order of 100 nanometers is a unique demonstration. Fig. 1 shows a schematic diagram of the experimental arrangement. An HP Model 3325A signal generator 4 drives the ultrasonic emitter with a 20-volt peak-to-peak sinewave tuned to a resonantly enhanced frequency in the response of the ultrasonic emitter/microphone combination. For the data shown here, we used a frequency of 153 kHz. A B&K microphone 5, type 4138 and its associated preamplifier type 2619, with a frequency response out to nearly 160 kHz, was used to detect the reflected ultrasound. For the greatest signal/noise, both the microphone and ultrasonic emitter were mounted close (approximately 2-3 mm) to the vibrating surface. The longitudinal symmetry axes of the microphone and emitter were at 20-30 degrees away from the normal to the vibrating surface. The microphone 5 was connected to its mating power supply/amplifier Model 2811. The preamplifier/amplifier combination was adjusted to pro...