BURIED SERVICE DETECTION

• US 20160109608A1
• Filed: 12/21/2015
• Published: 04/21/2016
• Est. Priority Date: 10/03/2014
• Status: Active Grant

• Current Assignee: Cable Detection Limited (Melker Schörling Tjänste AB)
• Original Assignee: Cable Detection Limited (Melker Schörling Tjänste AB)
• Inventors: BRANSON, Simon
• Granted Patent: US 10,209,385 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: E02F 9/245 for preventing damage to underground objects during excavation, e.g. indicating buried pipes or the like detection of pipes in the ground F16L1/11
• CPC Class Codes: G01V 13/00 Manufacturing, calibrating, cleaning, or repairing instruments or devices covered by groups G01V1/00 – G01V11/00
• CPC Class Codes: G01V 3/06 using ac
• CPC Class Codes: G01V 3/081 the magnetic field is produced by the objects or geological structures characterised by the method of magnetic field measurement G01R33/00
• CPC Class Codes: G01V 3/10 using induction coils
• CPC Class Codes: G01V 3/104 using several coupled or uncoupled coils G01V3/101 takes precedence
• CPC Class Codes: G01V 3/15 specially adapted for use during transport, e.g. by a person, vehicle or boat

Abstract

Some embodiments of the invention relate to a mobile detection device embodied as a bucket of an earth moving machine for an evaluation of a distance value and/or proximity from the bucket to an occluded AC-current carrying structure according to the magnetic field emanated from the structures AC-current. There is at least one detection coil, comprising at least one winding of an electrically conductive material, which is connected to a first amplification stage, with an amplifier circuit embodied as a current sensing amplifier, which are both are sealed within a common enclosure that is located at the bucket. An output of the amplifier circuit is configured to be linked to an electronic signal evaluation unit for detecting the occluded structure according to an electrical signal induced in the detection coil by the magnetic field.

Claims

1. A Mobile detection device as a bucket of an earth moving machine for an evaluation of a distance value and/or proximity from the bucket to an occluded AC-current carrying structure according to the magnetic field emanated from the structures AC-current, with

at least one detection coil, comprising at least one winding of an electrically conductive material, connected to

a first amplification stage,

wherein the detection coil and the first amplification stage are sealed within a common enclosure which is located at the bucket, and

wherein an output of the amplifier circuit is configured to be linked to an electronic signal evaluation unit for detecting the occluded structure according to an electrical signal induced in the detection coil by the magnetic field, and

wherein the first amplification stage is a amplifier circuit embodied as a current sensing amplifier.

2. The Mobile detection device according to claim 1, wherein the current sensing amplifier is characterized by having a low input impedance.

3. The Mobile detection device according to claim 1, wherein the detection coil is located at the cutting edge of the bucket.

4. The Mobile detection device according to claim 1, wherein the detection coil is located at one or more teeth of the bucket.

5. The Mobile detection device according to claim 1, wherein the detection device comprises at least a first and a second of the detection coils,

which are arranged at a fixed location at the bucket with a spacing with respect to one another, and

a distance value is evaluated by the evaluation unit according to a difference of the electrical signal in-between at least two of the detection coils, and

wherein the first detection coil is arranged at the bucket'"'"'s cutting edge and the second detection coil is arranged at the bucket'"'"'s top, back, or side.

6. The Mobile detection device according to claim 1, wherein the evaluation unit comprises a calibration unit built to successively configure one of the detection coils as transmitter for the calibration field, while detecting the calibration field with the remaining detection coil, wherein the electrical excitation signal is generated by a current signal generator.

7. The Mobile detection device according to claim 6, wherein the detection coil has a dedicated transmitter winding portion for application of the excitation signal and a dedicated receiver winding portion for detecting magnetic fields.

8. The Mobile detection device according to claim 1, wherein the detection device comprises at least a first, a second and a third detection coil, and the evaluation unit comprises a calibration unit built to successively apply the electrical excitation signal to one of the at least first, second or third detection coil to transmit a calibration field, which calibration field is detected by the at least two remaining of the detection coils to which the excitation signal is not applied, wherein calibration parameters for at least two of the coils are determined based on the detected calibration field.

9. The Mobile detection device according to claim 1 wherein the detection coils each has a winding count of 1 to 500 turns of a conductor with a cross-section of at least 0.1 mm².

10. The Mobile detection device according to claim 1, wherein

the current sensing amplifier is embodied as a transimpedance amplifier comprising an operational amplifier with a feedback network in a current to voltage configuration.

11. The Mobile detection device according to claim 10, wherein

the negative operational amplifier input is connected to one end of the coil and

the other end of the coil is connected to the positive operational amplifier input and

the operational amplifier output is fed back to the negative OpAmp input by a first, dominantly resistive and capacitive impedance.

12. The Mobile detection device according to claim 1, wherein

the current sensing amplifier is embodied with an input stage comprising a JFET in a feedback loop of a first operational amplifier stage in a current to voltage configuration.

13. The Mobile detection device according to claim 1, wherein

an output impedance of the detection coil is higher than an input impedance of the first amplification stage which the detection coil is connected to.

14. The Mobile detection device according to claim 1, wherein

the detection coil is embodied as tracks on a PCB.

15. The Mobile detection device according to claim 14, wherein

the same PCB also comprises the current sensing amplifier.

16. A location method for occluded AC-current carrying underground structures at a construction site during earth moving, with a mobile detection device embodied as a bucket of an earth moving machine,

wherein the bucket comprises at least one detection coil that is connected to a first amplification stage, with an amplifier circuit embodied as a current sensing amplifier, and

wherein the detection coil and the first amplification stage are sealed within a common enclosure that is located at the bucket, with a

detecting of the underground structure according to an electrical signal induced in the detection coil by a magnetic field emanated from the AC-current at the under ground structure,

the receiving and evaluating with the detection coils comprises an amplifying of the detection coils output in current mode by the current mode amplifier which is providing low input impedance to the detection coil, and

evaluating a proximity and/or a distance value from the bucket to the occluded AC-current carrying structure according to an electrical signal of the output of the current mode amplifier by means of an electronic signal evaluation unit.

17. The Method according to claim 16, wherein the providing of the low input impedance is established by a winding count of the coil which is below 500 turns and a winding cross-section of at least about 0.1 mm².

18. The Method according to claim 16, with the steps of

applying an electrical excitation signal to a first detection coil, which then acts as a magnetic field transmitter for a calibration field, and

receiving and evaluating the calibration field by at least one second detection coil, which is done multiple times with a permutation of the detection coils usage for transmitting or receiving, and

wherein a determining of calibration parameters for at least two of the detection coils is done by a calibration unit, based on a set of the evaluated calibration fields from each permutation.

19. The Method according to claim 16, wherein

the amplifying of the first amplification stage is tuned to have a substantially linear output over frequency in combination with the coil, for frequencies in the range of about 50 Hz to 250 kHz.

20. The Method according to claim 16, wherein

the detection coil and the current sensing amplifier are embodied as a single printed circuit board, which is located at the cutting edge of the bucket, and wherein an output of the current sensing amplifier is linked to the electronic signal evaluation unit which is located remote from the bucket at the earth moving machine.