CABLE DETECTION APPARATUS WITH A COMB FILTER

• US 20150234076A1
• Filed: 02/18/2015
• Published: 08/20/2015
• Est. Priority Date: 02/19/2014
• Status: Active Grant

• Current Assignee: Metrotech Corporation (L'Air Liquide SA)
• Original Assignee: Metrotech Corporation (L'Air Liquide SA)
• Inventors: OVERBY, Johan, ROYLE, John Mark
• Granted Patent: US 10,310,130 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• 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 3/10 using induction coils
• CPC Class Codes: G01V 3/12 operating with electromagnetic waves operating with millimetre waves G01V8/005

Abstract

An apparatus that uses harmonics of the power line frequency at which electrical power is distributed is presented. The apparatus includes a sensor antenna to detect an electromagnetic field produced by a cable. The output of the sensor is fed to a mixer together with a signal from a sine wave generator at less than the fundamental power frequency to frequency shift the signals from the sensor. The mixed output is then amplified to provide an audible output. A single comb filter receives signals from the mixer and outputs a filtered signal removing non-harmonic frequencies but preferably passing both odd and even harmonics. The output of the comb filter is then integrated at and displayed to indicate the detection of a cable based on the filtered signal.

Claims

1. A cable detection apparatus comprising:

a sensor to detect an electromagnetic field produced by a cable and provide signals;

a frequency shifter to frequency shift the signals from the sensor;

an amplifier that receives the frequency shifted signals;

a filter to receive signals from the amplifier and output a filtered signal, the filter having a higher transmittance at a plurality of harmonics of a first frequency than at least one non-harmonic frequency between two of said harmonics of the first frequency; and

an indicator to indicate the detection of a cable based on the filtered signal.

2. The cable detection apparatus of claim 1, wherein the filter has a higher transmittance at both odd and even harmonics of said first frequency than at least one non-harmonic frequency between two adjacent harmonics of the first frequency.

3. The cable detection apparatus of claim 1, wherein there is a single filter between the sensor and the indicator.

4. The cable detection apparatus of claim 1, wherein the filter is a comb filter.

5. The cable detection apparatus of claim 1, wherein the frequency shifter includes a mixer and a sine wave generator operating below a fundamental frequency.