Noncontact signal analyzer

• US 6,411,108 B1
• Filed: 03/28/2000
• Issued: 06/25/2002
• Est. Priority Date: 11/05/1999
• Status: Expired due to Term

• Current Assignee: Santronics Incorporated (Ninestar Corporation)
• Original Assignee: Sensory Technologies LLC (DSI Video Systems LLC)
• Inventors: Douglas, Philip, Beamer, Brent, Johnson, Alan G.
• Primary Examiner(s): Metjahic, Safet
• Assistant Examiner(s): PATEL, PARESH H
• Application Number:
  US09/536,562
• Publication Number:
  US 20020039028A1
• Time in Patent Office: 819 Days
• Field of Search: 76/11, 324/458, 324/690, 324/658, 324/669, 324/611, 324/750, 379/21
• US Class Current: 324/658
• CPC Class Codes: G01R 1/07 Non contact-making probes
• CPC Class Codes: G01R 31/312 by capacitive methods
• CPC Class Codes: H04B 3/46 Monitoring; Testing
• CPC Class Codes: H04B 5/22 Capacitive coupling
• CPC Class Codes: H04B 5/73 for taking measurements, e.g. using sensing coils
• CPC Class Codes: H04M 1/24 Arrangements for testing
• CPC Class Codes: H04M 2203/056 non-invasive testing, i.e. in operation testing without service interruption
• CPC Class Codes: H04M 3/22 Arrangements for supervision, monitoring or testing
• CPC Class Codes: H04M 3/2209 for lines also used for data transmission

Abstract

A noncontact sensor detects the signal waveform of analog and digital signals transmitted individually and, alternately, in combination, in designated transmission frequency bands on a pair of conductors.

Claims

1. Apparatus, for detecting the signal waveforms of analog and digital signals transmitted individually and, alternately, in combination, in designated transmission frequency bands on a pair of signal conductors, comprising:

a probe having first and second electrically conductive plates for capacitively coupling first and second signal samples of the transmitted signals in each designated transmission frequency band from the signal conductors to a related one of a pair of termination impedances associated with each plate, each plate further including an associated electrically conductive shield placed in spaced relation thereto;

signal conditioning circuitry, including first and second buffer amplifiers responsive, respectively, to said first and second sample signals at said termination impedances, for providing first and second equivalent sample signals thereof at an output of each amplifier, each said equivalent sample signal having equal signal polarity and substantially equal signal magnitude as its related sample signal, said buffer amplifiers each providing said equivalent sample signal to the commonly associated one of said electrically conductive shields, whereby the voltage signal potential of the conductive shield is substantially equal to the voltage signal potential of its associated plate, said signal conditioning circuitry further including a differential signal amplifier having first and second signal inputs responsive to said first and second equivalent sample signals, respectively, for providing a differential sample signal proportional to the difference sum therebetween;

a signal analyzer, for receiving said differential sample signal at each of one or more frequency filters, each said frequency filter having a passband which passes equivalent sample signal frequencies in one of the designated transmission frequency bands and rejects all other signal frequencies, said signal analyzer further including one or more signal annunciators associated with each said frequency filter, said signal annunciators indicating the presence of a designated transmission frequency band signal passed by its associated frequency filter; and

a sensor housing, for enclosing said signal conditioning circuitry and said signal analyzer within its main body and for enclosing said probe within a probe portion at one end thereof, said housing having a surface area for mounting said signal annunciators, and being adapted to be placed by a user in proximity to one or more conductors.

2. The apparatus of claim 1, wherein:

said signal analyzer provides said passed equivalent sample digital signals to an output thereof; and

said sensor housing further includes signal connectors for providing user access to the passed equivalent sample digital signals for purposes of supplemental signal analysis.

3. The apparatus of claim 1, wherein each said buffer amplifier is an operational amplifier having a minimum common mode input impedance of 10¹² ohms.

4. The apparatus of claim 1, wherein

each said buffer amplifier receives the sample signal from its associated conductive plate at a non-inverting signal input thereof;

and

each said termination impedance comprises a resistor connected in parallel with said buffer amplifier common mode input impedance, from said non-inverting signal input to signal ground.

5. The apparatus of claim 1, wherein said resistor has a minimum resistance value of one giga-ohm.

6. The apparatus of claim 1, wherein said annunciators comprise visual indicators.

7. The apparatus of claim 6, wherein said visual indicators comprise light emitting diodes.

8. The apparatus of claim 1, wherein said annunciators comprise aural indicators.

9. The apparatus of claim 8, wherein said aural indicators comprise a speaker.

10. The apparatus of claim 8, wherein said aural indicators comprise earphones.

11. The apparatus of claim 1, wherein said signal annunciators associated with each said frequency filter comprises a combination of a visual indicator and an aural indicator.

12. The apparatus of claim 1, wherein said housing comprises a plastic material.

13. The apparatus of claim 1, wherein said housing surface further includes a topical coating of an antistat agent.

14. The apparatus of claim 13, wherein said antistat agent is particularly applied to the surface of the housing probe portion.

15. The apparatus of claim 13, wherein the antistat agent is a surfactant.

16. The apparatus of claim 1, wherein each said conductive plate and its associated conductive shield are substantially planar.

17. The apparatus of claim 1, wherein each said conductive plate and its associated conductive shield are substantially curvilinear to permit cradling of a wire conductor by the conductive plate.

18. A method for detecting the signal waveforms of analog and digital signals transmitted individually and, alternately, in combination, in designated transmission frequency bands on a pair of conductors, comprising:

coupling, with capacitive means, a sample signal of the transmitted signals from a conductor to a termination impedance;

conditioning the sample signal at the termination impedance to provide an equivalent sample signal in the form of a low source impedance signal;

filtering the equivalent sample signal with a plurality of alternate bandpass frequency filters, each alternate bandpass being selected to pass equivalent sample signal frequencies in a different one of the designated transmission frequency bands, and to reject all other signal frequencies;

detecting the presence of a designated transmission frequency band signal passed by a filter; and

activating an annunciator to notify a user of the presence of a passed transmission frequency band signal.

19. The method of claim 18, wherein the step of coupling includes:

shielding the capacitive coupling means with a conductive shield to minimize electrostatic effects on the sample signal; and

energizing the conductive shield with the equivalent sample signal to minimize current leakage effects on the sample signal.

20. The apparatus of claim 19, wherein the step of conditioning includes:

presenting the sample signal from the termination impedance to the non-inverting signal input of an operational amplifier having a minimum common mode input impedance of 10¹² ohms.

21. The method of claim 20, wherein the step of coupling further includes:

providing the termination impedance as a resistor connected in parallel with the operational amplifier common mode input impedance, from said non-inverting signal input to signal ground.

22. The method of claim 21, wherein the resistor has a minimum resistance value of one giga-ohm.

23. The method of claim 19, further comprising:

using a housing to enclose the capacitive coupling means and its associated shield within a probe portion thereof, and to surface mount thereon the annunciators, and adapting the housing for placement by a user in proximity to one or more conductors.

24. The method of claim 23, further comprising:

presenting the equivalent sample digital signals to one or more output signal connectors on the housing; and

facilitating user access to the passed equivalent sample digital signals at the output signal connectors for purposes of supplemental signal analysis.

25. The method of claim 23, wherein the step of activating includes:

providing the annunciators as visual indicators and, alternately, as aural indicators and, alternately, as individual visual indicators and aural indicators.

26. The method of claim 25, wherein the step of activating includes:

embodying the aural indicator as a surface mounted speaker on the housing.

27. The method of claim 26, further comprising:

applying a topical coating of an antistat agent to the surface of the housing.

28. The method of claim 27, wherein the antistat agent is particularly applied to the surface of the housing probe portion.

29. The method of claim 27, wherein the antistat agent is a surfactant.

30. Apparatus, for detecting the signal waveforms of analog and digital signals transmitted individually and, alternately, in combination, in designated transmission frequency bands on a pair of conductors, comprising:

a housing, having an axially extending main body portion and a probe portion arranged in tandem therewith, said probe portion being adapted for placement by a user in proximity to the signal conductors, said housing further having a surface area adapted for mounting signal annunciators,

a substrate, adapted to be removably mounted within said housing, said substrate having mutually opposed major surfaces adapted to fit within said probe portion and said main body portion, said major surfaces being further adapted to receive thereon, in a surface mounted configuration, the components elements of;

a probe, having first and second plates disposed on opposite ones of said of mutually opposed major surfaces of said substrate, and each connected to an associated termination impedance, each said conductive plate having an associated electrically conductive shield disposed in spaced relationship therewith on said accompanying substrate major surface, said conductive plates being adapted to capacitively couple first and second signal samples of the transmitted signals in each designated transmission frequency band to said associated termination impedance in response to placement of said housing probe portion in proximity to the signal conductors; and

signal conditioning circuitry, including first and second buffer amplifiers responsive, respectively, to said first and second sample signals for providing first and second equivalent sample signals thereof at an output of each amplifier, each said equivalent sample signal having equal signal polarity and substantially equal signal magnitude as its related sample signal, said buffer amplifiers each providing said equivalent sample signal to the commonly associated one of said electrically conductive shields, whereby the voltage signal potential of the conductive shield is substantially equal to the voltage signal potential of its associated plate, said signal conditioning circuitry further including a differential signal amplifier having first and second signal inputs responsive to said first and second equivalent sample signals, respectively, for providing a differential sample signal proportional to the difference sum therebetween;

wherein said substrate includes conductive material traces disposed thereon to provide signal interconnection between each said conductive plate and its associated termination resistor and buffer amplifier, and wherein the periphery of said conductive plates and the conductive material trace signal connection between each plate and its termination resistor and buffer amplifier are bounded by a co-planar trace shield having an applied voltage potential which is substantially the same as the signal voltage potential of said conductive plates, as necessary, to minimize current leakage across said substrate major surfaces, between said conductive plates and interconnecting signal traces, and other substrate mounted apparatus; and

a signal analyzer, for receiving said equivalent sample signal at each of one or more frequency filters, each said frequency filter having a passband which passes equivalent sample signal frequencies in one of the designated transmission frequency bands and rejects all other signal frequencies, said signal analyzer further including one or more signal annunciators associated with each said frequency filter, said signal annunciators indicating the presence of a designated transmission frequency band signal passed by its associated frequency filter.

31. The apparatus of claim 30, wherein said substrate comprises a printed circuit board.

32. The apparatus of claim 31, wherein

each said buffer amplifier is an operational amplifier having a minimum common mode input impedance of 10¹² ohms.

33. The apparatus of claim 32, wherein

each said buffer amplifier receives the sample signal from its associated conductive plate at a non-inverting signal input thereof;

and

each said termination impedance comprises a resistor connected in parallel with said buffer amplifier common mode input impedance, from said non-inverting signal input to signal ground.

34. The apparatus of claim 33, wherein said resistor has a minimum resistance value of one giga-ohm.

35. The apparatus of claim 34, wherein said resistor comprises a carbon composition resistor.

36. The apparatus of claim 30, further comprising:

a sensor housing, for enclosing said substrate with said mounted probe, signal conditioning circuitry, and said signal analyzer, said housing having a surface area for mounting said signal annunciators, and being adapted to be placed by a user in proximity to one or more conductors.

37. The apparatus of claim 36, wherein:

said signal analyzer provides said passed equivalent sample digital signals to an output thereof; and

said sensor housing further includes signal connectors for providing user access to the passed equivalent sample digital signals for purposes of supplemental signal analysis.