Enhanced means of processing signals used to interpret the condition of machinery

• US 5,473,315 A
• Filed: 08/31/1994
• Issued: 12/05/1995
• Est. Priority Date: 09/23/1993
• Status: Expired due to Term

• Current Assignee: Holroyd Instruments Ltd. (Parker-Hannifin Corporation)
• Original Assignee: Holroyd Instruments Ltd. (Parker-Hannifin Corporation)
• Inventors: Holroyd, Trevor J.
• Primary Examiner(s): SWANN III, GLEN R
• Application Number:
  US08/298,947
• Time in Patent Office: 461 Days
• Field of Search: 340/683, 381/56
• US Class Current: 340/683
• CPC Class Codes: G01D 3/021 using purely analogue techniques
• CPC Class Codes: G01H 1/00 Measuring characteristics of vibrations in solids by using direct conduction to the detector G01H9/00, G01H11/00 take precedence
• CPC Class Codes: G01N 29/14 using acoustic emission techniques echo of particles G01N29/046; measuring mechanical vibrations or acoustic waves in solids in general G01H1/00
• CPC Class Codes: G01N 29/40 by amplitude filtering, e.g. by applying a threshold or by gain control

Abstract

A method of processing electrical signals which span a large dynamic range in order to enable the signal to be processed in its entirety without the need for any alteration to the signal gain or signal attenuation, comprises splitting of the signal along two or more paths each having a different amount of amplification or attenuation, the passing of each of these two or more different signals into one of two or more smaller dynamic range circuits which produce a logarithmically scaled representation of the average magnitude of the signal level at its input and the summation of the logarithmic outputs of the two or more smaller dynamic range circuits to produce a resultant logarithmically scaled signal representative of the average magnitude of the input signal over a very large dynamic range. The invention also includes apparatus for carrying out the above defined method.

Claims

1. A method of processing electrical signals which span a large dynamic range in order to enable the signal to be processed in its entirety without the need for the signal gain or signal attenuation to be dynamically altered by an amount determined by the signal level, comprises splitting of the signal along two or more paths each having a different amount of amplification or attenuation, the passing of each of these two or more different signals into one of two or more smaller dynamic range circuits which produce a logarithmically scaled representation of the average magnitude of the signal level at its input and the summation of the logarithmic outputs of the two or more smaller dynamic range circuits to produce a resultant logarithmically scaled signal representative of the average magnitude of the input signal over said large dynamic range.

2. A method as claimed in claim 1 in which the logarithmic outputs of the two or more smaller dynamic range circuits are adjusted by means of trimming the level of their DC voltage offsets with respect to each other in order to correct for minor errors in the level of their outputs in order to produce a resultant output which has the closest approximation to logarithmic scaling over the entire dynamic range of input signals after summation.

4. A method as claimed in claim 1 in which a difference in gains between the different signal paths is selected which is approximately equal to the usable dynamic range of each of the smaller dynamic range circuits.

5. A method as claimed in claim 1 in which the logarithmic outputs of the two or more smaller dynamic range circuits are clamped at preset values for signals outside their intended dynamic range such that the summed value of the two or more logarithmic outputs does not suffer errors due to over-range or under-range signals at the input of any of the smaller dynamic range circuits.

6. A method as claimed in claim 1 in which the electrical signals correspond to the acoustic emission or stress wave activity generated by an operating machine.

7. A method as claimed in claim 1 in which the electrical signals correspond to the vibrational activity generated by an operating machine.

8. A method as claimed in claim 1 in which the electrical signal correspond to the airborne noise generated by an operating machine.

9. An electronic apparatus for carrying out the method in claim 1 in which an electrical signal which spans a large dynamic range is processed in order to enable the signal in its entirety to be processed without the need for the signal gain or signal attenuation to be dynamically altered by an amount determined by the signal level, comprises means for splitting of the signal along two or more paths each having a different amount of amplification or attenuation, means to pass each of these two or more different signals into one of two or more smaller dynamic range circuits which produce a logarithmically scaled representation of the average magnitude of the signal level at its input and the summation of the logarithmic outputs of the two or more smaller dynamic range circuits to produce a resultant logarithmically scaled signal representative of the average magnitude of the input signal over said large dynamic range.

10. An apparatus as claimed in claim 9 in which the logarithmic outputs of the two or more smaller dynamic range circuits are adjusted by means of trimming the level of their DC voltage offsets with respect to each other in order to correct for minor errors in the level of their outputs in order to produce a resultant output which has the closest approximation to logarithmic scaling over the entire dynamic range of input signals after summation.

11. An apparatus as claimed in claim 9 in which the logarithmic outputs of the smaller dynamic range circuits correspond to the logarithmic value of the mean square of their respective input signals.

12. An apparatus as claimed in claim 9 in which a difference in gains between the different signal paths is selected which is approximately equal to the usable dynamic range of each of the smaller dynamic range circuits.

13. An apparatus as claimed in claim 9 in which the logarithmic outputs of the two or more smaller dynamic range circuits are clamped at preset values for signals outside their intended dynamic range such that the summed value of the two or more logarithmic outputs does not suffer errors due to over-range or under-range signals at the input of any of the smaller dynamic range circuits.

14. An apparatus as claimed in claim 9 comprising at least one transducer acoustically coupled to a process producing acoustic emissions and arranged to detect the acoustic emissions and to produce an electrical signal dependent upon the acoustic emission activity.

15. An apparatus as claimed in claim 9 comprising at least one accelerometer coupled to a process producing vibrations and arranged to detect the vibrations and to produce an electrical signal dependent upon the vibrational activity.

16. An apparatus as claimed in claim 9 comprising at least one microphone air coupled to a process producing noise and arranged to detect the airborne noise and to produce an electrical signal dependent upon the airborne noise activity.

17. An apparatus as claimed in claim 9 in which a means to determine the resultant logarithmically scaled signal representative of the average magnitude of the input signal over a very large dynamic range is used as part of equipment to determine the mechanical condition of operating machinery.

3. A method as claimed in claim I in which the logarithmic outputs of the smaller dynamic range circuits correspond to the logarithmic value of the mean square of their respective input signals.

18. An electronic apparatus for processing electrical signals which span a large dynamic range in order to enable the signal to be processed in its entirety without the need for the signal gain or signal attenuation to be dynamically altered by the amount determined by the signal level, said electronic apparatus comprising;

means for splitting of the signal along at least two paths, each path having a different amount of amplification or attenuation;

a smaller dynamic range circuit coupled to each of said at least two paths for producing a logarithmically-scaled representation of the average magnitude of the signal level at its input; and

means for summing logarithmically scaled representations coupled to the output of said at least two smaller dynamic range circuits for producing a resultant logarithmically-scaled signal representative of the average magnitude of the input signal over said large dynamic range.

19. An electronic apparatus for processing electrical signals spanning a large dynamic range which processes the signal in its entirety without the need for dynamically altering the signal gain or signal attenuation by an mount determined by the signal level, said electronic apparatus comprising;

input means for sensing physical phenomenon, such as acoustic emissions, vibration, and noise;

a first amplifier coupled to said input means;

a first root mean square to DC converter coupled to the said output of first amplifier;

a first precision clamp coupled to said first root mean square to DC converter;

a first DC offset timing circuit coupled to said first root mean square to DC converter;

a second amplifier coupled to the output of said first amplifier;

a second root mean square to DC converter coupled to said second amplifier;

a second DC offset timing circuit coupled to said second root mean squared DC converter;

a second precision clamp coupled to the output of said second root mean square to DC converter; and

a summing amplifier coupled to the outputs said first precision clamp and said second precision clamp producing an output voltage level equal to the sum of the output voltage levels from the first dynamic range circuit and from the second dynamic range circuit.