Piezoelectric ultrasonic apparatus and method for determining the distance from a predetermined point to a target

• US 4,567,766 A
• Filed: 03/20/1984
• Issued: 02/04/1986
• Est. Priority Date: 03/20/1984
• Status: Expired due to Fees

• Current Assignee: Blackwelders
• Original Assignee: Blackwelders
• Inventors: Seiferling, James E.
• Primary Examiner(s): Birmiel, Howard A.
• Application Number:
  US06/591,437
• Time in Patent Office: 686 Days
• Field of Search: 73/597, 73/598, 73/609, 73/610, 73/614, 367/122, 310/315
• US Class Current: 73/597
• CPC Class Codes: G01S 15/14 wherein a voltage or current pulse is initiated and terminated in accordance respectively with the pulse transmission and echo reception
• CPC Class Codes: G01S 7/52004 Means for monitoring or calibrating short-range imaging G01S7/5205
• CPC Class Codes: G01S 7/52006 with provision for compensating the effects of temperature

Abstract

A distance-determining detector and method. A piezoelectric ultrasonic transceiver sends out pulses and receives their reflection and produces an analog output and a trigger output. The analog output is given effect only when it exceeds a threshold level, as shown by a comparator. The trigger output is used for disabling detection during transmission of the transmitter pulse and for producing a time interval during which the analog output is valid, when enabled. An AND gate is connected to the comparator and to the enabled trigger output. Clock pulses are counted, and a flip-flop circuit is connected to the counter and to the output from the AND gate. A multiplying digital-to-analog converter is connected to the flip-flop circuit for determining the distance. There may also be temperature compensation and scaling for the converter for validating the output thereof over a wide range of temperatures.

Claims

1. A continuous distance determining detector for determining the distance from said detector to a target, including in combination:

a piezoelectric ultrasonic transceiver, having a pulse transmitter for sending a sonic pulse signal to said target, a pulse receiver for receiving a reflection of said pulse signal from said target, means for generating a voltage signal corresponding to the time between said transmission of said pulse signal and receipt of said reflected signal, an analog output and a trigger output means for producing a voltage signal at the time of transmission of said sonic pulse,

comparator means for comparing the voltage value of said analog output signal with a threshold level which must be exceeded by said analog output voltage before effect is given thereto,

disable means connected to said trigger output for disabling detection during transmission of the transmitter pulse,

enable means connected to the disable means for producing a time interval during which said analog output signal is valid,

an AND gate connected to said comparator means and to said enable means,

clock means for generating clock pulses,

counter means connected to said clock means for counting said clock pulses,

flip-flop means connected to said counter means and to the output of said AND gate and providing an output voltage,

temperature sensing means for sensing the ambient temperature,

temperature compensation and scaling means connected to said temperature sensing means for converting said ambient temperature into a correction voltage scaled to relate the ambient temperature to the output voltage of said flip-flop means, and

multiplying digital-to-analog converter means connected to said flip-flop means and to said temperature compensation and scaling means for correcting the output voltage value of said flip-flop means in accordance with the effect of said ambient temperature, and for determining a corrected value for the distance from said detector to said target.

2. The detector of claim 1 having first amplifying means between said transceiver and said comparator means, and second amplifier means for the output from said converter means.

3. The detector of claim 2 having means for adjusting said threshold level for said comparator means.

4. A method for instantaneously determining distance of an object from a given point, comprising:

transmitting from said given point a piezoelectric ultrasonic pulse to said object,

receiving the reflected pulse back therefrom at said given point,

producing an analog output voltage therefrom,

comparing said analog output voltage with a threshold level which must be exceeded by said analog output voltage before effect is given thereto,

disabling detection during transmission of the transmitter pulse,

enabling detection for a time interval during which said analog output is valid,

applying the disable-enable outputs and the comparing output to an AND gate,

generating clock pulses,

counting said clock pulses,

actuating the counting upon transmission of said pulse and de-actuating it upon receiving said pulse, to give the count during the interval between transmission and receiving,

determining the distance from the counts by comparing the time taken with the known speed at which the pulse travels, and

employing a multiplying analog-to-digital converter to temperature compensate the distance obtained from said determining step for validating the output thereof over a wide range of ambient temperatures and giving an accurate value of said distance of said object from said given point.

5. The method of claim 4 including the preliminary step of adjusting the threshold voltage level for said comparing step to proper value for the type of said object to which said method is applied.