What is correlation? Precise water leak location with Digital Signal Processing
Correlation is a method for finding and pinpointing water leaks in pipes.
A water leak in a pipe under pressure creates noise that travels along the pipe, its contents, and through the surrounding ground.
When two highly sensitive microphones are attached to a water pipe with a leak betwen them the sound from the water leak takes longer to travel to the microphone furthest from the water leak; this is called the “time delay” or ∆t.
Utilising this and other known information (water pipe diameter, material and length), the exact water leak position can be automatically calculated by the water leak correlator SeCorrPhon® AC200
Two highly sensitive microphones are attached by magnet, or valve adaptors, to suitable listening positions such as hydrants, valves, the water pipe walls or even directly into the water column using hydrophone sensors. The water leak must be between the two microphones. As long as the water leak noise can be “heard” and recognised by both microphones (correlated) the SeCorrPhon AC200 can process and analyse the resulting information.
The water leak sounds picked up by the microphones are transmitted via two powerful 500 mW radio transmitters to the lightweight central processing unit SeCorrPhon AC200 Digital Signal Processor where the noise information is quickly analysed & the resulting water leak position is displayed both graphically and numerically, as metres to the leak from each sensor.
SeCorrPhon AC200 - Radio transmitters and Piezo accelerometers
The noise from the microphones is transmitted to the central control processor by two powerful radio transmitters
- Lightweight radio transmitters which can easily be carried in one hand by the antenna carrying buttons
- Automatic on/off when the microphone is plugged in/out - no danger of running the battery flat by mistake
- Automatic best amplification level selected when microphone connected
- In built low pass frequency filter - Ideal for plastic pipes; It highlights and emphasises sounds in the range 0-300 Hz which is where leak noises are more likely to be propagated on this material
- The receiver and radio transmitters can all be charged in the closed case doing away with the nuisance of having multiple component parts plugged into various sockets around your office.
- Charging can also be carried out in your car or van via the 12V cigar lighter lead
Hydrophones
Best performance for finding water leaks in plastic pipes
- Hydrophones are microphones which are attached, via hydrants, directly into the water column (as opposed to on the external surface of the pipe) so even very quiet water leak noise can be heard far more successfully.
- They are particularly useful on plastic pipes and trunk mains where sounds does not travel as well as on cast and steel pipes
SeCorrPhon AC200 - Firmware and Software
With the SeCorrPhon AC200 software you can:
- Analyse field tests on your PC or laptop. This can be very useful where a test gives a good indication of a water leak but the other input data is unreliable, such as pipe material, or size. The results can be re-calculated back in the office to give the correct water leak location without the need to carry out another correlation. This can be carried out on the PC or on the SeCorrPhon AC200 itself
- Reports: PC software produces clear reports including: Your address, client’s address, operator, leak location, material, diameter, coherence, correlation and a pictorial representation of the water leak location.
- Record leak noise: Real water leak noise sound can be recorded which allows users to listen to noises away from the field for later comment and interpretation, perhaps by more experienced staff
- Zoom: Zoom function on display - Gives added clarity to suspect readings
Minimum Noise Level Memory Function - Assistance In Finding Water Leaks
Current “lowest” noise level: - A water leak noise does not get quieter but traffic and wind noise will increase and decrease.
The SeCorrPhon AC200 ignores all these interfering noises, digitally displaying only the “quietest” it has been during the time you have been listening. The current “actual” noise level is also displayed as an analogue bar graph. This is a constantly moving display depending on ambient noise levels.
Memory: The last lowest noise level is stored and displayed. Are you closer or further away from the water leak in the current listening position compared to the last?
Is the leak sound getting louder or quieter? The higher the number on the display the closer to the water leak you are.
Amplification: There are three levels of amplification (as well as the volume control). The amplification level can be selected to best suit the noise level being listened to.
Dynamic Hearing Protection Function
With normal acoustic water leak detection instruments an uncomfortable, sometimes painful and dangerous, noise is heard when the test rod slips from the contact point, or the headphones are activated too soon, or not soon enough, or some comedian bangs their foot to see if you "Can hear that?".
The SeCorrPhon AC200 incorporates a novel technology to makes this danger a thing of the past. When a very loud noise is picked up the sound in the headphones is immediately muffled. If the sound increases even further, the headphones are switched off completely.
Frequency Filter - Water Leak Noise Optimised Listening
We do not all hear best at the same frequencies; some people prefer listening at high frequencies others to lower.
Leaks do not all produce noise at the same frequency.
Sometimes interfering noises make listening at certain frequencies very difficult.
The SeCorrPhon AC200® has a number of ways to assist with all these problems...
...SUIT YOURSELF:
By applying your own choice of frequency filters you can listen to any frequency range that you wish which best suits the leak noise being listened to, your hearing and to filter out interfering noises, all selected by the push of a button.
...LET THE SeCorrPhon AC200 HELP:
If you are unsure of what frequency filters to use the SeCorrPhon can help you decide.
The filter-optimisation function makes it easier to detect water leaks even when the sound is very muffled. By activating the frequency filter button the receiver takes a noise sample which is analysed & the optimum frequency range is set. This can greatly assist those with less experience making the sound of the water leak clearer.
...AUTOMATIC BEST SETTINGS:
When a microphone is plugged in the SeCorrPhon AC200 ® automatically recognises which model it is and sets the best filter range. If you have chosen an alternative setting it defaults to the last settings you chose. The SeCorrPhon even turns itself on and off when you plug the microphone in or out.
SeCorrPhon AC200 WATER LEAK LOCATOR FEATURES
- Very quick and easy to use intuitive operation sequence
- Input data via tcoloured touch screen
- Automatic background interference noise suppression
- Utilises the latest Digital Signal Processor (DSP) provides fast accurate calculations ensuring quicker leak location
- Fast Fourier Transformation (FFT) correlation – precise fast location even with the most challenging leaks
- Large illuminated TFT colour display min. 5.7” – Clear precise visualisation of leaks, even in bright sunlight
- “Highest Peak” (likely leak location) automatically selected- This can be moved by the operator to look at other suspicious indications
- Many “Drill down menu” advanced features, comparable to PC driven correlators, are available for times that you need to use their advantages, and out of the way when you do not
SeCorrPhon AC200 - Technical Information Receiver
- Display Large illuminated TFT colour display min. 5.7”
- PC connection for information download wreless connection for optional valve and ground microphones
- Built in rechargable Li batteries Approx. 10 hours use
- Digital 2.4 GHz wireless headphones (not bluetooth)
- Operating temperature: -20 °C … +60 °C
- Protection class: IP 67
- Weight: approx. 1.25 kg
SeCorrPhon AC200 - Technical Information Radio transmitter
- Automatically on when microphone connected
- Selectable low-pass filter to increase performance on non-metallic water pipes
- GPS positioining in transmitter
- 500 mW output power
- Operating tgemperature -20 °C … +60 °C
- Protection class: IP 67
- Weight: approx. 0.45 kg
- Operating time: approx. 8 hours
