Scheme for low power strain measurement

1 . A method of determining a parameter, comprising:

a. providing a sensor that provides a sensor analog voltage;

b. providing a peak detecting circuit for detecting a peak voltage in said sensor analog voltage;

c. providing said sensor analog voltage to said peak detecting circuit and detecting said peak voltage; and

d. recording said peak voltage.

2 . A method as recited in claim 1 , wherein after said recording said peak voltage (d) further comprising resetting said peak detecting circuit for detecting another peak voltage in said sensor analog voltage.

3 . A method as recited in claim 2 , wherein said circuit includes a resetting switch for resetting said peak detecting circuit.

4 . A method as recited in claim 1 , wherein said circuit stores a present sensor analog voltage peak value and repeatedly compares said sensor analog voltage with said present sensor analog voltage peak value, wherein said present sensor analog voltage peak value is determined to be said peak voltage when said sensor analog voltage falls a specified amount below said present sensor analog voltage peak value.

5 . A method as recited in claim 4 , wherein said circuit includes an amplifier for storing said present analog voltage peak value.

6 . A method as recited in claim 5 , wherein said circuit includes a comparator, wherein said comparator includes a first input and a second input, wherein said first input is for said sensor analog voltage and wherein said second input is for said present sensor analog voltage peak value.

7 . A method as recited in claim 6 , wherein said circuit draws less than 4 microamps.

8 . A method as recited in claim 1 , wherein said sensor is sensitive to strain and wherein said sensor analog voltage is related to strain.

9 . A method as recited in claim 1 , wherein said sensor is sensitive to loading and wherein said sensor analog voltage is related to loading.

10 . A method as recited in claim 9 , wherein said sensor measures change in loading without power consumption.

11 . A method as recited in claim 1 , further comprising:

e. providing a valley detecting circuit for detecting a valley voltage in said sensor analog voltage;

f. providing said sensor analog voltage to said valley detecting circuit and detecting said valley voltage; and

g. recording said valley voltage.

12 . A method as recited in claim 11 , wherein said sensor is mounted on a component, wherein said sensor is sensitive to strain, and wherein said sensor analog voltage is related to strain, further comprising using said recorded peak voltage and said recorded valley voltage to determine a parameter related to fatigue life.

13 . A method as recited in claim 12 , further comprising measuring a static strain and using both said static strain and a plurality of recorded peak voltages and recorded valley voltages to determine said parameter related to fatigue life.

14 . A method as recited in claim 12 , further comprising measuring mean load and using both said mean load and a plurality of recorded peak voltages and recorded valley voltages to determine said parameter related to fatigue life.

15 . A method as recited in claim 12 , wherein said parameter related to fatigue life includes at least one from the group consisting of remaining life and fatigue life expended.

16 . A method as recited in claim 1 , wherein said sensor is mounted on a component, wherein said component is for rotating.

17 . A method as recited in claim 16 , wherein said component includes at least one from the group consisting of a shaft, a gear, a wind turbine blade, a helicopter blade, a helicopter structural component, a sporting equipment, a hand tool, an instrumented bolt, a tire, a wheel, and a machine tool.

18 . A method as recited in claim 1 , wherein said sensor is self-powering.

19 . A method as recited in claim 18 , wherein said sensor includes a piezo-electric element.

20 . A method of determining a parameter, comprising:

a. providing a sensor that provides a sensor analog voltage;

b. providing a circuit for detecting a feature of said sensor analog voltage;

c. providing said sensor analog voltage to said peak detecting circuit and detecting said feature; and

d. using said feature to provide timing for when to record data from said sensor.

21 . A method as recited in claim 20 , wherein said feature is at least one from the group consisting of a peak sensor analog voltage and a valley sensor analog voltage.

22 . A method as recited in claim 21 , further comprising recording at least one from the group consisting of said peak sensor analog voltage and said valley sensor analog voltage.

23 . A method as recited in claim 20 , wherein said sensor provides said sensor analog voltage without consuming power.

24 . A method as recited in claim 23 , further comprising providing a power consuming sensor for providing a second measurement and providing power for making said second measurement.

25 . A method as recited in claim 24 , further comprising using said feature to provide timing for providing power to said power consuming sensor for making said second measurement.

26 . A method as recited in claim 25 , further comprising recording said second measurement and turning off power to said power consuming sensor after said recording said measurement.

27 . A method of determining a parameter, comprising:

a. providing a dynamic analog sensor;

b. providing a circuit for detecting at least one from the group consisting of peaks and valleys of data from said dynamic analog sensor; and

c. recording data from said dynamic analog sensor only when said circuit detects at least one from the group consisting of peaks and valleys of data from said dynamic analog sensor.

28 . A method as recited in claim 27 , further comprising providing a power consuming sensor for providing a second measurement and providing power for making said second measurement.

29 . A method as recited in claim 28 , further comprising using detection of at least one from the group consisting of peaks and valleys of data from said dynamic analog sensor to provide timing for providing power to said power consuming sensor for making said second measurement.

30 . A method as recited in claim 29 , further comprising recording said second measurement and turning off power to said power consuming sensor after said recording said measurement.

31 . A system, comprising a device, an electronic circuit, a first strain gauge and a second strain gauge, wherein said electronic circuit, said first strain gauge, and said second strain gauge are mounted on said device, wherein said first strain gauge consumes power for its operation and wherein said second strain gauge consumes no power for its operation, wherein said electronic circuit is connected to receive data from said first strain gauge and from said second strain gauge.

32 . A system as recited in claim 31 , wherein said first strain gauge includes a piezoresistive strain gauge and wherein said second strain gauge includes a piezoelectric strain gauge.

33 . A system as recited in claim 31 , wherein said electronic circuit includes a processor, wherein said processor is configured for taking data from said first strain gauge and from said second strain gauge, wherein said processor includes a program that uses data from both said first strain gauge and from said second strain gauge for determining a parameter.

34 . A system as recited in claim 33 , wherein said processor includes a program to sample data from said first strain gauge less frequently than from said second strain gauge.

35 . A system as recited in claim 33 , wherein said device has geometrical and material properties, wherein said parameter is a fatigue life parameter of said device, wherein said processor has a program to use said data along with said properties to compute said fatigue life parameter of said device.

36 . A system as recited in claim 35 , wherein said fatigue life parameter includes fatigue life expended.

37 . A system as recited in claim 35 , further comprising a non-volatile display, wherein said display is mounted on said device, wherein said processor includes a program to update said display with said fatigue life parameter.

38 . A system as recited in claim 31 , further comprising an energy harvesting device, wherein said energy harvesting device is connected to provide power for operating said electronic circuit.

39 . A system as recited in claim 38 , wherein said energy harvesting device collects energy from one from the group consisting of strain and vibration.

40 . A method of monitoring a structure comprising:

a. providing a structure having a component;

b. mounting a sensor to said structure, wherein said sensor provides an analog voltage related to loading;

c. mounting a peak detecting circuit to said structure wherein said peak detecting circuit is for detecting a peak voltage in said analog voltage related to loading;

d. providing said analog voltage related to loading to said peak detecting circuit and detecting said peak voltage; and

e. using said peak voltage in determining a parameter related to severity of usage of said component.

41 . A method as recited in claim 40 , further comprising recording data derived from said sensor related to loading.

42 . A method as recited in claim 40 , further comprising replacing said component if information derived from said recorded data shows that said component experienced a load history indicating damaging usage.

43 . A method of operating a system as recited in claim 42 , wherein said load history indicating damaging usage includes a load exceeding a threshold.

44 . A method of operating a system as recited in claim 42 , wherein said load history indicating damaging usage includes fatigue inducing cyclic loading.

45 . A method as recited in claim 40 , further comprising mounting an energy harvesting device to said structure,

46 . A method as recited in claim 45 , wherein said energy harvesting device is configured to convert at least one from the group consisting of vibration of the structure and strain of the structure into electricity.

47 . A method as recited in claim 45 , wherein said peak detecting circuit is powered solely with electricity derived from said energy harvesting device.

48 . A method of operating a system as recited in claim 45 , further comprising mounting a wireless communications device to said structure, and further comprising transmitting data derived from said sensor with said wireless communications device, wherein all power for powering said wireless communications device is derived from said energy harvesting device.

49 . A method as recited in claim 40 , wherein said sensor is self-powering.

50 . A method as recited in claim 40 , further comprising mounting a display to said structure and displaying said parameter related to fatigue life of said component.