System for locating multiple concealed underground objects

• US 5,361,029 A
• Filed: 06/22/1992
• Issued: 11/01/1994
• Est. Priority Date: 06/18/1990
• Status: Expired due to Term

• Current Assignee: Charles Machine Works Inc (Toro)
• Original Assignee: Charles Machine Works Inc (Toro)
• Inventors: Rider, Alan J., Querry, Lester R.
• Primary Examiner(s): Strecker, Gerard R.
• Application Number:
  US07/902,525
• Time in Patent Office: 862 Days
• Field of Search: 324/66, 324/67, 324/232, 324/326-329, 324/335, 379/25, 455/101, 455/103, 455/193
• US Class Current: 324/326
• CPC Class Codes: G01R 31/60 Identification of wires in a multicore cable
• 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

An improved locator system is provided which simultaneously couples a number of different frequency signals to a number of concealed underground conductive lines, for the purpose of locating and distinguishing between the underground lines. The locator system includes a transmitter which generates the different frequency signals for coupling to the underground lines. A receiver is also provided that detects the different frequency signals and distinguishes between the underground lines. The locator system further provides an arrangement for operating at virtually any frequency within the locating band, and for preselecting an operating frequency that avoids interference from extraneous signals.

Claims

1. A locator system for use in locating and distinguishing between a plurality of underground objects by detecting a plurality of electromagnetic signals radiated from said plurality of underground objects, each of said plurality of electromagnetic signals having a given frequency, the frequency of each of said electromagnetic signals being individually selectable, said system comprising:

programmable generating means for generating said plurality of electrical signals, where each electrical signal can be of a different frequency, and when said electrical signals are coupled to respective underground objects, corresponding electromagnetic signals are radiated from said plurality of underground objects, said programmable generating means further comprising respective signal sources for generating said plurality of electrical signals;

a processor responsive to a command for programming the programmable generating means to select frequencies for generation by the programmable generating means;

means for coupling each selected electrical signal to a different one of said plurality of underground objects such that a different electromagnetic signal is simultaneously radiated from each underground object of said plurality of underground objects; and

at least one receiver means movable above the ground in the vicinity of the underground objects for detecting one electromagnetic signal and reject detecting of the other radiated electromagnetic signals in order to locate and distinguish between said plurality of underground objects.

11. The locator system according to claim 1 wherein said programmable generating means comprises a plurality of frequency synthesizers, and each said frequency synthesizer is uniquely associated with an output of the programmable generating means.

12. The locator system according to claim 1 wherein said programmable generating means generates an output digital signal of a programmed frequency, and further including a programmable filter for converting the digital signal to a corresponding analog signal.

13. The locator system according to claim 1 wherein said programmable generating means generates a precision frequency electrical signal, and said receiver means includes a band pass filter to pass the frequency of the radiated electromagnetic signal and reject similar frequencies of interference signals.

14. The locator system according to claim 13 wherein said receiver means band pass filter is programmable according to the frequency of the radiated electromagnetic signals received by the receiver means.

15. The locator system according to claim 14 wherein said receiver means further includes an antenna that is programmably tuned according to the frequency of the radiated electromagnetic signals received by the receiver means.

2. A locator system for locating and distinguishing between a plurality of underground objects, said system comprising:

multi-frequency signal generator means adapted for generating a first plurality of signals of different frequencies;

selector means for identifying signals of different frequencies of said signal generator means from the first plurality of signals, whereby said signal generator means generates the different frequencies identified;

transmitting means for transmitting said identified signals, said transmitting means having a plurality of outputs for simultaneously transmitting identified signals of different frequencies;

output coupling means for coupling said identified signals from said multi-frequency signal generator means to said transmitting means so that the transmitter means transmits the respective identified signals to the respective outputs of the transmitter means;

transmitter coupling means coupled to said plurality of outputs of said transmitting means for coupling the transmitted signals to said plurality of underground objects for radiating said identified signals from said plurality of underground objects;

receiver sensing means for sensing at least one of the radiated signals and producing a representative signal representing one of said sensed radiated signals

receiver amplifying means for amplifying said representative signal;

receiver gain control means for controlling the gain of said amplified representative signal; and

receiver identifying means coupled to said amplifying means for identifying the frequency of said sensed radiated signals from said amplified representative signal and distinguishing the identified signal from other signals radiated from the underground objects.

3. The locator system according to claim 2 wherein said multi-frequency signal generator means comprises at least one frequency synthesizer means.

4. The locator system according to claim 2 wherein said multi-signal selector means comprises a microprocessing means.

5. The locator system according to claim 2 further including output control means coupled to said transmitter for controlling the power of the transmitted signals.

6. The locator system according to claim 2 wherein said selector means automatically identifies a signal frequency that is electrically separated from a power line signal harmonic frequency.

7. A method for use in a system for locating and distinguishing between a plurality of underground objects, said method comprising the steps of:

generating a first plurality of signals of different frequencies with a multi-frequency generator;

selecting signals of different frequencies from the first plurality of signals;

coupling each said selected signal generated by said multi-frequency signal generator to a respective transmitter of a plurality of transmitters;

coupling each transmitted signal from a respective transmitter to a different one of said plurality of underground objects such that said transmitted signals cause respective electromagnetic radiations from said underground objects;

moving a receiver above ground in the vicinity of the underground objects;

sensing the electromagnetic radiations radiate therefrom and producing a representative signal representing at least one of said sensed electromagnetic radiations;

amplifying said representative signal with an amplifier;

controlling the gain of said amplified representative signal;

determining the frequency of said representative signal; and

providing to a user an indication of the frequency of the sensed representative signal.

8. A transmitter for use in a system for locating and distinguishing between a plurality of underground objects, said transmitter comprising:

multi-frequency signal generator means adapted for generating a range of signals of different frequencies;

programming means for programming said multi-frequency signal generator to produce plural, different signals of different frequencies from said range of signal frequencies;

transmitting means having multiple outputs for respectively transmitting said programmed signals so that each said transmitter means output transmits a different frequency;

coupling means for coupling said selected signals from said multi-frequency signal generator means to said transmitting means; and

radiating means coupling said plurality of outputs of said transmitting means to said plurality of underground objects for causing electromagnetic signals of different frequencies to be radiated respectively from said plurality of underground objects.

9. A method for use with a transmitter used for locating and distinguishing between a plurality of underground objects, said method comprising the steps of:

programming a multi-frequency generator capable of generating a range of frequencies to generate a subset of frequencies defining a first plurality of digital signals, each characterized by a different frequency;

filtering each frequency of the subset with a different filter;

programming each filter individually to provide a corresponding analog signal output therefrom;

transmitting each said analog signal from said programmed filters to a different output of a plurality of outputs; and

coupling each said transmitted signal to a different underground object such that said analog signals radiate from said plurality of underground objects.

10. A locator system for use in locating a plurality of underground objects, said system comprising:

a transmitter including,

at least one frequency synthesizer for generating a subset of different frequencies from a plurality of precisely defined available frequencies;

transmitting means for transmitting the subset of frequencies to said plurality of underground objects such that each said underground object radiates a respective frequency of the subset; and

a receiver including,

a frequency synthesizer programmable to produce different and precise frequencies for tuning the receiver to a narrow band pass to process any one of the radiated frequencies and reject the other radiated frequencies.

16. A method of locating a plurality of underground conductors using a locator system employing a transmitter and a receiver, comprising the steps of:

a) selecting plural different frequencies to be transmitted by the transmitter;

b) generating the plural different frequencies by the transmitter;

individually filtering the plural different frequencies to define analog waveforms of the plural different frequencies;

d) amplifying the plural analog waveforms of the different frequencies;

e) coupling each amplified analog waveform to a different one of said underground conductors so that the frequencies are simultaneously radiated respectively from the respective underground conductors;

f) selecting in the receiver one of the plural frequencies coupled to the underground conductors so that the receiver senses the selected frequency and rejects other frequencies;

g) carrying the receiver above ground in the vicinity of the underground conductors;

h) providing in the receiver an indication of the proximity of the underground conductor radiating the frequency selected in the receiver;

i) selecting in the receiver another one of the plural frequencies coupled to the underground conductors; and

j) repeating steps g) and h).