Device and method for acoustically measuring distance

• US 20070097790A1
• Filed: 11/01/2005
• Published: 05/03/2007
• Est. Priority Date: 11/01/2005
• Status: Active Grant

• Current Assignee: Techtronic Cordless GP (Techtronic Industries Company Limited)
• Original Assignee: Solar Wide Industrial Ltd. (Techtronic Industries Company Limited)
• Inventors: Sanoner, Hughes, Yim, Ronald, Tse, Desmond
• Granted Patent: US 7,263,031 B2
• Time in Patent Office: Days
• US Class Current: 367/99
• CPC Class Codes: G01S 7/52006 with provision for compensating the effects of temperature
• CPC Class Codes: G01S 7/529 Gain of receiver varied automatically during pulse-recurrence period for seismic signals G01V1/245
• CPC Class Codes: Y10S 367/902 Speed of sound compensation

Abstract

A method of acoustically obtaining a distance to an object includes transmitting through air an acoustic signal towards an object and receiving a reflected acoustic signal reflected from the object. The time from transmitting the acoustic signal to receiving the reflected acoustic signal is determined. The temperature of the air is determined and used to determined velocity of the acoustic signal. The distance to the object is calculated using the time and the velocity.

Claims

1. A distance measuring device comprising:

an acoustic signal transmitter for transmitting an acoustic signal towards a distant object,

an acoustic signal receiver for receiving a reflected acoustic signal reflected from the distant object,

a temperature sensor for detecting air temperature,

a humidity sensor for detecting air humidity,

an amplifier coupled to the receiver for amplifying the reflected acoustic signal to produce an amplified reflected acoustic signal,

a comparator coupled to the amplifier for comparing level of the amplified reflected acoustic signal with a reference level and generating a comparator output when the level of the amplified reflected acoustic signal exceeds the reference level,

a gain controller for controlling gain of the amplifier and increasing the gain from time of transmitting an acoustic signal towards a distant object until the comparator output is generated,

a threshold generator for providing the reference level to the comparator based on both the air temperature detected and the air humidity detected and decreasing the reference level at an exponential rate of decrease from the time of transmitting the acoustic signal until the comparator output is generated, and

a controller for determining use of only the air temperature detected, velocity of the acoustic signal, and distance travelled from the time of transmitting the acoustic signal until the comparator output is generated.

2. The distance measuring device of claim 1 wherein the gain controller comprises a plurality of independently switchable resistors connected in parallel and a capacitor connected in series with the resistors.

3. The distance measuring device of claim 1 wherein the threshold generator comprises a current source, a plurality of independently switchable resistors, and a capacitor connected in parallel with the resistors.

4. A method of acoustically obtaining a distance to an object comprising:

transmitting through air an acoustic signal towards an object,

receiving a reflected acoustic signal reflected from the object,

determining whether the reflected acoustic signal is a valid reflected signal and generating a received signal,

determining time from transmitting the acoustic signal until the received signal is generated,

determining temperature of the air and using the temperature to determine velocity of the acoustic signal, and

calculating distance to the object using the time and the velocity.

5. The method of claim 4 including repeating the steps to calculate a second distance to the object, and, if the second distance is the same as the distances, communicating the distance to a person obtaining the distance.

6. The method of claim 4 wherein the velocity is determined using the equation:

velocity=331.45×

Sqr((temperature+273.16)/273.16).

7. The method of claim 4 including, in response to a user input, continuously calculating a new distance to the object and communicating the new distance to a person obtaining the distance.

8. The method of claim 4 wherein determining whether the reflected acoustic signal is a valid reflected acoustic signal comprises providing an amplifier having a gain for amplifying the reflected acoustic signal.

9. The method of claim 8 further including increasing the gain during the time from transmitting the acoustic signal until the received signal is generated.

10. The method of claim 4 wherein determining whether the reflected acoustic signal is a valid reflected signal comprises amplifying the reflected signal to produce an amplified signal, comparing level of the amplified signal to a reference level and generating the received signal when the level of the amplified signal exceeds the reference level.

11. The method of claim 10 including determining humidity of the air and using the temperature and the humidity to determine an initial value of the reference level and decreasing the reference level at an exponential rate of decrease from the time of transmitting the acoustic signal until the received signal is generated.

12. A method of acoustically obtaining a distance to an object comprising:

transmitting through air an acoustic signal towards an object,

receiving a reflected acoustic signal reflected from the object,

amplifying the reflected signal to produce an amplified signal,

comparing level of the amplified signal to a reference level and generating a received signal when the level of the amplified signal exceeds the reference level,

determining time from transmitting the acoustic signal until the received signal is generated,

determining temperature of the air and using the temperature to determine velocity of the acoustic signal, and

calculating distance to the object using the time and the velocity.

13. A method of acoustically obtaining a distance to an object comprising:

transmitting through air an acoustic signal towards an object,

receiving a reflected acoustic signal reflected from the object,

determining time from transmitting the acoustic signal to receiving the reflected acoustic signal,

determining temperature of the air and using the temperature to determine velocity of the acoustic signal,

calculating distance to the object using the time and the velocity and communicating the distance to a person obtaining the distance, and

continuously repeating the foregoing steps to calculate an updated distance to the object and communicating the updated distance to the person obtaining the distance.