Abstract Method and apparatus for measuring the difference in length between two paths through sound transmitting medium. In one embodiment, a U-tube manometer has transducers placed near the bottoms of the columns of liquid in the two manometer legs. An electronic circuit causes the transducers to emit simultaneous sound signals directed toward the tops of the columns. A counter accumulates a count of the pulses produced by a high frequency oscillator between the time the echo of the sound signal in the short column of liquid is received by its transducer and the time the echo in the long column of liquid is received by its transducer. The count is indicative of the difference in height between the two columns, and thus of the difference between the pressures applied to the two manometer legs. The count may be displayed in conventional units of pressure, or it may be utilized in any other suitable manner. In alternative embodiments, the sound signals may be allowed to travel two or more times between the transducers and the free surfaces of the columns before being used to initiate or terminate the counting of high frequency pulses. The manometer is enclosed in a double walled cabinet and the temperature of the liquid columns is maintained constant by a heater which is controlled by a system providing both off-on and proportional heat controls. The U-tube manometer may be filled with mercury. A transducer satisfying the special requirements due to the use of mercury is also described.
In an ultrasonic measuring device for transducing between sound energy propogating in a column of mercury at ground electrical potential and an electrical potential developed across transducer electrode means, said transducer comprising: a. a wafer of piezoelectric ceramic material having opposed flat faces oriented parallel to the upper surface of the mercury column; b. a silver coating covering each of the opposing faces of the wafer and in intimate contact therewith; c. a thin platinum foil; d. a layer of electrically conductive metal-filled epoxy material cementing said platinum foil to the upper silvered face of said wafer whereby said platinum foil is in intimate wetted contact with the mercury to define a first electrode; e. a mounting structure of sound absorbing insulative plastic material having a flat surface cemented to the second silvered surface of said wafer and including an opening extending therethrough communicating with said second silvered surface. f. an electrical lead extending through the opening in the mounting structure and in electrical contact with said second silver coated surface to define a second electrode electrically insulated from said first electrode and the mercury. g. a seal extending from the mounting structure to the edges of the platinum electrode peripherally insulating the margins of said wafer from the mercury, and h. means for applying electrical impulses across said wafer and receiving electrical impulses produced by echoes of sound vibrations impinging upon the platinum electrode to yield clean fundamental frequency bursts of sound wih a minimum of ringing.
Claim 2
Dependent Claim
248 words
In an ultrasonic measuring device for transducing between sound energy propogating in a column of mercury at ground electrical potential and an electrical potential developed across transducer electrode means, said transducer comprising: a. a wafer of piezoelectric ceramic material having opposed flat faces oriented parallel to the upper surface of the mercury column; b. a silver coating covering each of the opposing faces of the wafer and in intimate contact therewith; c. a thin platinum foil; d. a layer of electrically conductive metal-filled epoxy material cementing said platinum foil to the upper silvered face of said wafer whereby said platinum foil is in intimate wetted contact with the mercury to define a first electrode; e. a mounting structure of sound absorbing insulative plastic material having a flat surface cemented to the second silvered surface of said wafer and including an opening extending therethrough communicating with said second silvered surface. f. an electrical lead extending through the opening in the mounting structure and in electrical contact with said second silver coated surface to define a second electrode electrically insulated from said first electrode and the mercury. g. a seal extending from the mounting structure to the edges of the platinum electrode peripherally insulating the margins of said wafer from the mercury, and h. means for applying electrical impulses across said wafer and receiving electrical impulses produced by echoes of sound vibrations impinging upon the platinum electrode to yield clean fundamental frequency bursts of sound wih a minimum of ringing.
Claim 3
Dependent Claim
38 words
The transducing device of claim 1, in which the piezoelectric material is a fired body of polycrystalline lead titanate-lead zirconate polarized to afford linear piezoelectric response between electrical fields across said electrodes and thickness deformations in said wafer.
Claim 4
Dependent Claim
16 words
The transducing device of claim 2 wherein the mounting structure is comprised of a phenolic resin.