Acoustic length measurement

Acoustic measurement of sewer pipes

Several years of joint development by the institute and an industrial partner have resulted in a new device for measuring pipelines with acoustic noise. From the outset, this project was considered to be very innovative and outstanding, so that the Federal Ministry of Economics and Technology had promised funding for development on the basis of a resolution of the German Bundestag.

The acoustic measuring system called Soundcheck detects the pipe diameter, posture length, temperature and air flow in the pipe within a few seconds at the push of a button. The complete technology is housed in a 3D prototyping housing, which is lowered down the shaft by means of a telescopic rod and placed at the beginning of the pipe. At the push of a button, the measurement starts and the data is transmitted by radio to a PC at the top of the shaft a few seconds later. Digital signal processing is used to determine the above-mentioned characteristics from the collected data. These are displayed and output in a user interface.

The tube length is determined by the transit time measurement. A transmitter is attached to the starting shaft and a receiver to the end shaft, which are connected to each other by radio frequency. This method measures the time required for an acoustic signal to pass through the measuring section from transmitter to receiver.

By measuring the pipe diameter, temperature and air flow, the position can be precisely determined along its length.



In addition, a receiver is located directly in front of the transmitter, with which the response signal (the reflections in the tube) is measured. Included in the response signal are impedance jumps caused by irregularities such as transitions, joints, side branches, dimensional jumps. However, this information cannot be used directly. In order to make the information provided in the impedance jumps usable for the user, it must first be interpreted and evaluated by means of electronic signal processing and analysis algorithms.



In the near future, two prototypes will be tested by test companies under real operating conditions. In the same way, measurement data are determined which is to help further develop the analysis of molded parts.