Leak detection apparatus and method

• US 6,820,016 B2
• Filed: 05/01/2003
• Issued: 11/16/2004
• Est. Priority Date: 06/26/2000
• Status: Expired due to Fees

• Current Assignee: Palmer Environmental Ltd. (Halma PLC)
• Original Assignee: Palmer Environmental Ltd. (Halma PLC)
• Inventors: Brown, Ian J., Williams, Andrew J., Smith, Brynley D.
• Primary Examiner(s): Barlow, John
• Assistant Examiner(s): Walling, Meagan S
• Application Number:
  US10/311,891
• Publication Number:
  US 20030167847A1
• Time in Patent Office: 565 Days
• Field of Search: 702/35, 702/36, 702/50, 702/51, 702/54, 73/405.R, 73/405.A, 735/92, 340/605
• US Class Current: 702/51
• CPC Class Codes: G01M 3/243 for pipes

Abstract

An apparatus and method for detecting a leak in a pipe, the apparatus comprising a sensor (11) located at a pipe (7), configured to detect a signal from the pipe, converter means to convert the signal detected by the sensor into a digital signal, and transform means to transform the digital signal into a different orthogonal space. The apparatus also comprises a transmitter (15) for transmitting the transformed digital signal back to a remote processor.

Claims

1. An apparatus for detecting a leak in a pipe, the apparatus comprising:

a sensor located at a pipe configured to detect a signal from a pipe;

converter means to convert the signal detected by the sensor into a digital signal;

transform means for transforming the digital signal into a different orthogonal space; and

a transmitter for transmitting the transformed digital signal back to a remote processor;

wherein the transform means is configured to perform a wavelet transform in which the digital signal is transformed according to the general formula;

$\begin{array}{cc}f<br><br>\left(t\right)=\underset{k=-\mathrm{\infty <br><br>}}{\overset{\mathrm{\infty <br><br>}}{\sum <br><br>}}<br><br>\text{\hspace{1em}<br><br>}<br><br>c_k<br><br>\mathrm{\varphi <br><br>}<br><br>\left(t-k\right)+\underset{k=-\mathrm{\infty <br><br>}}{\overset{\mathrm{\infty <br><br>}}{\sum <br><br>}}<br><br>\underset{j=0}{\overset{\mathrm{\infty <br><br>}}{\sum <br><br>}}<br><br>\text{\hspace{1em}<br><br>}<br><br>d_{j,k}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\psi <br><br>}<br><br>\left(2^j<br><br>t-k\right)& \left(1\right)\end{array}$

where (ft) represents the digital signal outputted by the analogue to digital conversion means, t is the time, φ

(t−

k) and ψ

(2^jt−

k) functions represent the mother scaling functions and wavelet functions repsectively and the coeffricients c_k and d_j,k are calculated from the inner product of f(t) with the scaling functions and wavelet functions respectively such that;

2. An apparatus according to claim 1, wherein the transform means uses a transform which forms an unconditional basis for the signal.

3. An apparatus according to claim 1, wherein the transform means is configured to perform a Fourier transform.

4. An apparatus according to claim 1, wherein the wavelet function has substantially a harmonic form.

5. An apparatus according to claim 1, wherein the output from the transform means is directed into a scalar quantiser which is configured to quantise the data.

6. An apparatus according to claim 1, wherein the sensor and the converter means are provided in a sensor module located at the pipe.

7. An apparatus according to claim 6, the transmitter being connected to the sensor via a cable which is capable of carrying digital signals.

8. A corrrelator for detecting and determining the position of a leak in a pipe, the correlator comprising:

a plurality of apparatus according to claim 1,

a remote processor capable of receiving a signal transmitted from at least two adjacent apparatus and which is capable of comparing the signals received from the two adjacent apparatus.

9. A correlator according to claim 8, wherein the remote processor is capable of receiving signals from the at least two apparatus when the remote processor is moving.

10. An apparatus for detecting a leak in a pipe, the apparatus comprising:

a sensor located at a pipe configured to detect a signal from a pipe;

converter means to convert the signal detected by the sensor into a digital signal;

transform means for transforming the digital signal into a different orthogonal space; and

a transmitter for transmitting the transformed digital signal back to a remote processor;

further comprising encoder means for compressing the signal from the transform means, wherein the encoder means is configured to perform a loss less compression technique, wherein the loss less compression technique is a hierarchical coding technique comprising Huffman coding or a technique based on Huffman coding and wherein the encoding technique comprises the steps of;

a) converting digitised data into an array of numbers, each number being assigned an index;

b) determining a first threshold value;

c) locating the last number in the array which is greater than the said threshold value;

d) adding the index of the said last number onto the data stream to be transmitted;

e) adding the numbers of the array upt to and including the said last number, wherein numbers below the threshold being added as a 0 and numbers above the threshold being added as a bit number with the sign of the number being encoded in the last bit;

f) setting a second threshold value wherein said second threshold is less than the first threshold; and

g) repeating steps c) to f) until a predetermined final threshold is reached.

11. A corrrelator for detecting and determining the position of a leak in a pipe, the correlator comprising:

a plurality of apparatus according to claim 10,

a remote processor capable of receiving a signal transmitted from at least two adjacent apparatus and which is capable of comparing the signals received from the two adjacent apparatus.

12. A correlator according to claim 11, wherein the remote processor is capable of receiving signals from the at least two apparatus when the remote processor is moving.

13. An apparatus for detecting a leak in a pipe, the apparatus comprising:

a sensor located at a pipe configured to detect a signal from a pipe;

converter means to convert the signal detected by the sensor into a digital signal;

transform means for transforming the digital signal into a different orthogonal space; and

a transmitter for transmitting the transformed digital signal back to a remote processor;

wherein the sensor comprises a compressible member, wherein compression and expansion of the member causes an electric signal to be generated, the member being at least partially compressed when located in a position at the pipe.

14. An apparatus according to claim 13, wherein said sensor is provided in a sensor module, said sensor module having a biasing member which is configured to bias the compressible member against a rigid part of the sensor module.

15. An apparatus according to claim 14, wherein a compressible sealing member is provided for the sensor module, and said sealing member is used to bias said compressible member.

16. A corrrelator for detecting and determining the position of a leak in a pipe, the correlator comprising:

a plurality of apparatus according to claim 13,

a remote processor capable of receiving a signal transmitted from at least two adjacent apparatus and which is capable of comparing the signals received from the two adjacent apparatus.

17. A correlator according to claim 16, wherein the remote processor is capable of receiving signals from the at least two apparatus when the remote processor is moving.