Title:
METHOD AND INSTRUMENT FOR MEASURING INTERNAL STATE OF DUCT LINE
Document Type and Number:
Japanese Patent JP3175878
Kind Code:
B2
Abstract:
PURPOSE: To simplify the measurement and investigation of a duct line and reduce the manpower required for the measurement and investigation by discriminating objects in the duct line and the end of the duct line from the relations between the waveform of acoustic waves made incident to the duct line and waveforms of reflected acoustic waves from the objects and end of the duct line.
CONSTITUTION: Acoustic waves made incident on an underground communication duct line 21 from a loudspeaker 1 installed to a prescribed position of a manhole 20 are reflected by internal reflecting objects P1-P3 (respectively indicating the positions of a dent 101, foreign matter 102, and coupling 103) and the, end of the line P4 (indicating the end of the line) after passing through the location P0 of a microphone 2 and again measured at the microphone 2. The positions of the reflecting objects P1-P3 can be discriminated from the time lags of the measured reflected acoustic waves and the difference among the objects can be discriminated from the waveforms of the reflected acoustic waves. In other words, the distances 11-14 from the position P0 of the microphone 2 to the objects P1-P3 and end P4 can be calculated from the acoustic velocity and time lags between the acoustic waves passing through the microphone 2 and reflected acoustic waves from the objects P1-P3 and end P4. The acoustic velocity can be calculated from the temperature in the duct line measured with a temperature sensor 3.
Inventors:
Tetsuya Manabe
Shigeru Tomita
Ken Tsujimura
Tetsuro Yabuta
Shigeru Tomita
Ken Tsujimura
Tetsuro Yabuta
Application Number:
JP19955793A
Publication Date:
June 11, 2001
Filing Date:
August 11, 1993
Export Citation:
Assignee:
Nippon Telegraph and Telephone Corporation
International Classes:
G01S15/06; G01B17/00; G01S7/526; G01S15/88; (IPC1-7): G01S15/06; G01S7/526; G01S15/88
Domestic Patent References:
| JP4297815A | ||||
| JP5273335A | ||||
| JP5306923A | ||||
| JP514962U |
Other References:
【文献】特許3034330(JP,B2)
Attorney, Agent or Firm:
Shuuki Akita