Rate of ascent monitor using piezoelectric transducer

• US 4,820,953 A
• Filed: 11/23/1987
• Issued: 04/11/1989
• Est. Priority Date: 11/23/1987
• Status: Expired due to Fees

• Current Assignee: Stitma Scientific Incorporated
• Original Assignee: Italo D.E. Blasi, Malcolm Saubolle, Stanley Livshitz
• Inventors: Saubolle, Malcolm, Livshitz, Stanley, De Blasi, Italo
• Primary Examiner(s): Budd, Mark O.
• Application Number:
  US07/124,050
• Time in Patent Office: 505 Days
• Field of Search: 310/337, 310/338, 310/339, 310/324, 310/330-332, 364/418, 367/134, 73/290 V, 73/291, 73/495, 73/502, 73/517 R, 73/517 AV, 73/715, 73/723, 73/754, 73/DIG. 4
• US Class Current: 310/338
• CPC Class Codes: B06B 1/0666 used as a diaphragm
• CPC Class Codes: G01L 9/008 using piezoelectric devices piezoelectric resonators G01L9/0022; surface acoustic waves G01L9/0025
• CPC Class Codes: G01P 3/62 Devices characterised by the determination or the variation of atmospheric pressure with height to measure the vertical components of speed measuring pressure in general G01L

Abstract

A rate of ascent monitor for drivers uses a sound transducer with velocity characteristics, preferably a diaphragm type piezoelectric transducer, to sense rate of pressure change, and a threshold detector connected to the transducer to drive an indicator providing a warning of an excessive rate of ascent. A second threshold detector can be used to discriminate between descending and ascending motion. The device can be a compact wrist mounted unit.

Claims

1. A submersible rate of ascent monitor for divers, comprising a body defining a chamber, a diaphragm of a piezoelectric sound transducer closing an opening in said body so as hermetically to seal the chamber from the surrounding water, a piezoelectric ceramic wafer of the sound transducer being bonded to the inside surface of the diaphragm, a low pass filter electrically connected to the transducer output to exclude therefrom signals due to sounds, water movements and impacts, a threshold detector circuit within the chamber and receiving an output of the low pass filter, said threshold detector having a first threshold corresponding to a rate of decrease of ambient pressure indicative of an excessive rate of ascent, and indicator means driven by the threshold detector circuit to indicate an excessive rate of descent.

2. A monitor according to claim 1, wherein the threshold detector circuit has a second threshold corresponding to a very small or zero rate of pressure change, and further indicator means driven by said threshold detector to indicate whether a diver is ascending or descending.

3. A monitor according to claim 1, wherein the ceramic wafer is covered with a moisture resistant dielectric layer.

4. A monitor according to claim 1, including a wrist strap for securing the monitor to the wrist of a user.