The invention relates to a method and apparatus for determining the phase
5 compositions of a multiphase fluid flow, in particular, although not exclusively, to a
method and apparatus for determining the dryness of wet steam.
The use of steam as a heating medium in industrial processes is very widespread.
Most process and heating steam systems use saturated wet steam which is a two-
10 phase fluid comprising vapour as a first phase and condensate as a second phase.
It is often necessary to know the dryness, or quality, of the wet steam. Steam quality is
the percentage of the mass of the fluid that is vapour, and therefore saturated steam
has a steam quality of 100% and saturated liquid has a steam quality of 0%.
15
Some industrial processes have particular requirements regarding steam quality. For
example, in sterilisation systems the steam quality must be between 95%-100%. This
is set-out by standard BS EN 285 which specifies the requirements and relevant tests
for large steam sterilisers primarily used in health care. Currently, steam quality is
20 typically measured using throttling calorimetry. An example of an apparatus and
method for measuring steam quality using a throttling calorimeter is disclosed in
GB 1906 12,615. Whilst throttling calorimetry can be used to successfully determine
the quality of steam, it is a time-consuming process and the apparatus is relatively
complicated.
25
It is therefore desirable to provide an improved method and apparatus for determining
the phase compositions of a multiphase fluid flow.
The invention is defined in the attached independent claims to which reference should
30 now be made. Further, preferred features may be found in the sub-claims appended
thereto.
In a broad aspect the invention concerns a method and apparatus for determining the
phase compositions (which may be the dryness) of a multiphase fluid flow, such as wet
35 steam, from the characteristics of one or more vibration signals obtained from the fluid
flow.
ORIGINAL
According to an aspect of the invention there is provided a method of determining the
phase compositions (which may be the dryness) of a multiphase fluid flow in a fluid
line, comprising: obtaining a vibration signal from the fluid flow using a vibration sensor
5 comprising a target disposed in the fluid flow which vibrates in response to fluid flow in
the fluid line; analysing the vibration signal to determine a first energy parameter which
is related to the energy of the vibration signal within a first frequency band, and a
second energy parameter which is related to the energy of the vibration signal within a
second frequency band; and determining a phase composition parameter (which may
10 be a dryness parameter) relating to the phase compositions (which may be the
dryness) of the fluid flow using the first and second energy parameters. The phase
composition parameter may be determined empirically from the first and second energy
parameters.
15 The target may be a diaphragm. The vibration sensor may further comprise an
electrical converter for converting the vibration of the target into a vibration signal. The
electrical converter may comprise a piezoelectric transducer. The first and/or second
frequency band may be a single frequency or a range of frequencies. The first and/or
second energy parameter may be any suitable parameter that can be derived or
20 determined from the vibration signal and which can be related together to arrive at the
phase compositions/dryness of the fluid flow.
In some embodiments, but not necessarily in all embodiments, the target may vibrate in
response to fluid flow impact on the target. The target may be configured to resonate
25 at one or more resonant frequencies. The vibration signal may be analysed to
determine a first and/or a second energy parameter which is the amplitude of one or
more resonant frequencies of the vibration signal.
The fluid flow may be mixed upstream of the vibration sensor. This may help to ensure
30 that the fluid flowing in the line is substantially uniform.
The vibration sensor may measure the vibration signal in the time domain. Analysing
the vibration signal may include transforming the vibration signal from the time domain
to the frequency domain. The vibration signal may be transformed from the time
35 domain to the frequency domain using a fast Fourier transform (FFT).
ORIGINAL
The first energy parameter may be dependent on the flow velocity. This may mean
that the first energy parameter may change in response to a change in the flow
velocity. The second energy parameter may be dependent on the phase compositions
of the fluid flow and the flow velocity. In other words, the second energy parameter
5 may change in response to a change in either the flow velocity or the phase
compositions of the fluid flow.
The first energy parameter may be the total energy of the vibration signal within the first
frequency band and the second energy parameter may be the total energy of the
10 vibration signal within the second frequency band. The total energy may be
determined by summing the amplitudes of all of the frequencies with the particular
frequency band. The first energy parameter may be the amplitude of the peak
frequency within the first frequency band and the second energy parameter may be the
amplitude of the peak frequency within the second frequency band. In other
15 embodiments, the first and/or second energy parameter may be the average amplitude
of all frequencies within the particular band, or may be any other suitable value capable
of characterising the energy of the vibration signal within the particular frequency band.
The first frequency band and/or the second frequency band may be predetermined or
20 fixed for a particular installation. Analysing the vibration signal may include defining the
first frequency band about a first peak frequency and/or defining the second frequency
band about a second peak frequency. The method may include detecting a first and/or
a second peak frequency. The first frequency band may contain a first peak frequency
and/or the second frequency band may contain a second peak frequency. The first
25 frequency band may be at a lower frequency than the second frequency band.
The method may further comprise determining a temperature parameter relating to the
temperature of the fluid flow. The phase composition and/or dryness parameter may
be determined by using a first energy parameter, a second energy parameter and the
30 temperature parameter. The temperature parameter may be an actual temperature, or
may be some other parameter that is related to temperature, for example pressure.
Determining a phase composition and/or a dryness parameter may comprise accessing
a database containing data correlating first energy parameters and second energy
35 parameters with phase composition parameters. If the multiphase fluid is wet steam,
the dryness parameter may be expressed as a percentage where 100% is saturated
ORIGINAL
vapour and where 0% is saturated liquid. The dryness parameter may be known as
"steam quality".
The method may further comprise outputting the phase composition and/or dryness
5 parameter. Outputting the phase composition andlor dryness parameter may comprise
displaying andlor transmitting the phase composition and/or dryness parameter. The
phase composition and/or dryness parameter may be transmitted wirelessly.
The fluid flow may be a steam flow, such as wet steam. The dryness parameter may
10 be known as the "vapour quality".
According to another aspect of the invention there is provided an apparatus for
determining the phase compositions (which may be the dryness) of a multiphase fluid
flow flowing in a fluid line, comprising: a vibration sensor comprising a target arranged
15 to be disposed in the fluid flow which vibrates in response to fluid flow in the fluid line
for obtaining a vibration signal from the fluid flow; a vibration signal analysis unit for
analysing the vibration signal to determine a first energy parameter which is related to
the energy of the vibration signal within a first frequency band, and a second energy
parameter which is related to the energy of the vibration signal within a second
20 frequency band; and a phase composition determining unit (which may be a dryness
determining unit) for determining a phase composition parameter (which may be a
dryness parameter) relating to the phase compositions (which may be the dryness) of
the fluid flow using the first and second energy parameters.
25 The apparatus may further comprise a fluid mixer for mixing the fluid flow upstream of
the vibration sensor.
The vibration sensor may be arranged to measure the vibration signal in the time
domain. The vibration signal analysis unit may be arranged to transform the vibration
30 signal from the time domain to the frequency domain. The vibration signal analysis unit
may be arranged to transform the vibration signal from the time domain to the
frequency domain using a fast Fourier transform (FFT).
The first energy parameter may be dependent on the flow velocity. The second energy
35 parameter may be dependent on the phase compositions of the fluid flow and the flow
velocity. The first energy parameter may be the total energy of the vibration signal
ORIGINAL
within the first frequency band and the second energy parameter may be the total
energy of the vibration signal within the second frequency band. The first energy
parameter may be the amplitude of the peak frequency within the first frequency band
and the second energy parameter may be the amplitude of the peak frequency within
5 the second frequency band. The first frequency band may be predetermined and the
second frequency band may be predetermined. The vibration signal analysis unit may
be arranged to define the first frequency band about a first peak frequency and the
vibration signal analysis unit may be arranged to define the second frequency band
about a second peak frequency. The first frequency band may contain a first peak
10 frequency and the second frequency band may contain a second peak frequency. The
first frequency band may be at a lower frequency than the second frequency band.
The apparatus may further comprise a database containing data correlating first energy
parameters and second energy parameters with phase composition and/or dryness
15 parameters. The phase composition and/or dryness determining unit may be arranged
to access the database so as to determine a phase composition andlor dryness
parameter relating to the phase compositions and/or dryness of the fluid flow.
The apparatus may further comprise an outputting unit for outputting the phase
20 composition and/or dryness parameter. The outputting unit may comprise a display for
displaying the phase composition and/or dryness parameter and/or a transmitter for
transmitting the phase composition and/or dryness parameter.
The apparatus may be arranged to determine the phase compositions and/or the
25 dryness of a steam flow.
The apparatus may further comprise a length of pipe having connectors at either end,
wherein the target is disposed within the pipe. A fluid mixer may be disposed within the
pipe in front of the target. The distance between the connectors may be in accordance
30 within a predetermined standard.
The target may be a diaphragm. In some embodiments the target may be arranged to
resonate in response to fluid flow impact. The vibration sensor may further comprise
an electrical converter for converting the vibration of the target into a vibration signal.
35 The electrical converter may comprise a piezoelectric transducer.
ORIGINAL
The invention also concerns a steam system comprising an apparatus in accordance
with any statement herein.
The invention may comprise any combination of the features andlor limitations referred
5 to herein, except combinations of such features as are mutually exclusive.
Embodiments of the invention will now be described, by way of example, with reference
to the accompanying drawings, in which:
10 Figure 1 schematically shows an apparatus for determining the dryness of wet steam
flowing in a steam line;
Figure 2 schematically shows the vibration sensor of Figure 1 ;
15 Figure 3 schematically shows a vibration signal obtained by the vibration sensor in the
time domain; and
Figure 4 schematically shows three vibration signals obtained by the vibration sensor in
the frequency domain.
20
Figure 1 shows generally at 10 an apparatus for determining the phase compositions
of wet steam flowing in a steam line. In this particular embodiment the apparatus 10 is
arranged to determine the dryness of the wet steam. The apparatus 10 comprises a
length of pipe 12 having connection flanges 14, 16 at either end. The apparatus 10
25 further comprises a vibration sensor 22 for obtaining a vibration signal from the steam
flow and a fluid mixer 20 located upstream for mixing the steam flow.
The vibration sensor 22 is disposed within the pipe 12 downstream of the mixer 20 in
the longitudinal direction of the pipe 12 and is shown in more detail in Figure 2. The
30 vibration sensor 22 comprises a hollow stem 34 that extends into the pipe and a head
36 which is mounted onto the end of the stem 34 and which is aligned with the axis of
the pipe. The head 36 comprises a body 37 and a substantially planar target 38 which
is in the form of a diaphragm. The target 38 faces the steam flow and lies in a plane
perpendicular to the steam flow direction. The target 38 is arranged to vibrate in
35 response to fluid flow within the pipe. A piezoelectric transducer 40 is mounted within
the body 37 and is coupled to the target 38 such that vibration of the target 38 in the
ORIGINAL
axial direction is converted into an electrical vibration signal. Signal wires (not shown)
are connected to the piezoelectric transducer 40 and pass down the hollow stem 34 to
extend to the outside of the pipe 12. The stem 34 and head 36 are manufactured from
stainless steel and the diaphragm target 38 is a thin metallic plate.
5
In this embodiment the apparatus 10 is an integrated unit which can be easily installed
in a new steam installation, or can be retrofitted to an existing steam installation, by
connecting the flanges 14, 16 to corresponding connection flanges of a steam line such
that the pipe 12 forms part of the steam line 12. However, it should be appreciated that
10 in other embodiments the apparatus may be supplied as a series of separate
components that must be installed and wired together individually.
In use, the fluid flow within the steam line causes the target 38 to vibrate in the axial
direction. If the fluid is wet steam, the fluid flow contains both water droplets and
15 vapour. It has been found by experiment that the electrical vibration signal generated
by the target 38 contains characteristics relating primarily to the flow velocity, and
characteristics relating to a combination of the dryness of the steam and the flow
velocity. Therefore, by using these characteristics, the apparatus 10 can be used to
determine the dryness of the steam. In order to ensure that the fluid flow is
20 substantially uniform across the cross-sectional area of the pipe 12, a fluid mixer 20 is
disposed in the pipe 12 upstream of the vibration sensor 22. The fluid mixer 20 helps
to ensure that no condensate slugs pass under the vibration sensor 22 which would
lead to the apparatus determining a steam dryness value higher than the actual value.
25 The vibration sensor 22 outputs the electrical vibration signal in the time domain and a
graphical representation of such a signal is shown in Figure 3. This vibration signal is
output to a vibration signal analysis unit 42. The analysis unit 42 transforms the
vibration signal from the time domain to the frequency domain using a fast Fourier
transform (FFT) algorithm. A graphical representation of three different vibration
30 signals in the frequency domain is shown in Figure 4. The three different vibration
signals correspond to three different steam flows having different steam dryness
values.
As can be seen from Figure 4, the target 38 vibrates at a first peak frequency and at a
35 second peak frequency that are both substantially the same for all three dryness
ORIGINAL
values. However, the energy of the vibration signals (i.e. the amplitude of the first and
second peak frequencies) changes depending on the steam dryness value.
After transforming the vibration signal to the frequency domain, the analysis unit 42
5 determines the energy of the vibration signal within two predefined frequency bands B1
and 82 that contain the first and second peak frequencies respectively. It has been
found by experiment that the vibration signal within the first frequency band B1 is
characteristic of the flow velocity only, whereas the vibration signal within the second
frequency band B2 (which is at a higher frequency) is characteristic of the phase
10 compositions and the flow velocity. The energy of the vibration signal within the first
and second frequency bands B1, B2 is calculated by summing the individual
amplitudes of all of the individual frequencies within the particular frequency band B1,
B2. In this particular embodiment the first frequency band B1 is 0-4kHz and the
second frequency band 82 is 26-46 kHz. However, it should be appreciated that other
15 frequency bands may be used, as the frequency bands may depend on the particular
construction of the vibration sensor and the steam installation as a whole. The energy
of the vibration signal within the first frequency band B1 is termed a "first energy
parameter El" and the energy of the vibration signal within the second frequency band
62 is termed a "second energy parameter E2". The first energy parameter El is
20 dependent on the flow velocity of the steam flow, and the second energy parameter is
dependent on both the phase compositions, or steam dryness value, of the steam flow,
and the flow velocity of the steam flow.
In this embodiment the first frequency band B1 and the second frequency band B2 are
25 defined as a range of frequencies, but in other embodiments one or both of the
frequency bands could be a single frequency. However, if a FFT is used to transform
the vibration signal from the time domain to the frequency domain, if one or more of the
frequency bands are defined as a single frequency this will in fact correspond to a
range of frequencies defined by the resolution of the FFT. One or both of the
30 frequency bands can be fixed for a particular installation as the peak frequencies are
substantially independent of the flow velocity and dryness. However, it may be
necessary to change one or both of the frequency bands if the installation changes. In
other embodiments, the analysis unit 42 may identify a first peak frequency and/or a
second peak frequency, and define the first frequency band B1 about the first peak
35 frequency and/or the second frequency band about the second peak frequency B2.
ORIGINAL
Although it has been described that the first and second energy parameters El, E2 are
the energies of the vibration signal within first and second frequency bands B1, 82
respectively, the first and/or second energy parameter may be any suitable parameter
that is related to the energy of the vibration signal and which can be related with one
another, to obtain a value representing the dryness of the steam. In some embodiment
the first and second energy parameters may be calculated using different methods.
For example, the first energy parameter may be the amplitude of the first peak
frequency, whereas the second energy parameter may be the average amplitude of the
frequencies within the second frequency band. Of course, any other suitable value
could be used.
The first energy parameter El and the second energy parameter E2 determined by the
vibration signal analysis unit 42 are output to a dryness determining unit 44. The
dryness determining unit 44 takes the two energy parameters El, E2 and accesses a
database 46 in order to empirically determine the dryness of the steam. The database
46 contains a look-up table that contains reference or calibration data that correlates a
range of first energy parameters El and second energy parameters E2 with steam
dryness values. The reference or calibration data is data obtained by experimentation.
The determining unit 44 determines the steam dryness value from the data in the lookup
table and displays this dryness value on a local display 48. In addition to this, the
dryness value is transmitted to a control room via a wireless connection using a
wireless transmitter 50. This allows the steam dryness to be remotely monitored. In
some embodiments the first energy parameter El may be converted to an actual flow
velocity which is also output on the display. The flow velocity could be calculated or
determined empirically from the first energy parameter El. It should be appreciated
that the look-up table may contain data that correlates a range of flow velocities and
second energy parameters E2 with steam dryness values. As opposed to determining
and outputting a dryness parameter, other parameters that express the phase
compositions of the multiphase flow may be determined and output.
The dryness determining unit 44 is also configured to calculate the mass flow rate of
the steam flow based on the steam dryness value and the flow velocity which may be
determined from the first energy parameter El. The mass flow rate may also be
displayed on the display 48 and may also be transmitted using the transmitter 50.
ORIGINAL
The look-up table contained within the database 46 is created empirically. It may be
necessary to create a new look-up table for each apparatus 10. However, it may be
possible to produce a generic look-up table suitable for all apparatuses. In order to
create the look-up table, a series of pre-determined volumes of water are injected into
5 the steam line at range of flow velocities and for each combination of water
volume/velocity the first energy parameter El and the second energy parameter E2 are
recorded. The steam quality (or dryness) can be calculated from the known water
volume and therefore by this calibration method a look-up table providing correlations
between various first and second energy parameters El, E2 can be created.
10
Although the peak frequencies of the target 38 remain substantially constant regardless
of steam dryness, slight variations may occur in the peak frequencies if a film of water,
for example, builds up on the face of the target 38. Further, a change in temperature of
the target 38 may cause its mechanical properties to change which may also result in
15 the peak frequencies shifting. It may be possible to determine the temperature of the
steam from one or a combination of one or more peak frequencies.
In some arrangements it is possible that the first and second energy parameters El, E2
are a function of the temperature, as well as of the flow velocity, and the dryness and
20 flow velocity. If this is the case, a temperature sensor may be provided to measure the
temperature of the steam. In such an arrangement the database 46 would contain a
"three-dimensional" look-up table correlating first energy parameters El (or flow
velocities), second energy parameters E2 and temperatures with dryness parameters.
Instead of using a temperature sensor, it may be possible to use a pressure sensor and
25 calculate (or estimate) the temperature from this, or the temperature (or pressure) may
be determined from a peak frequency.
Although it has been described that the method and apparatus can be used for
measuring the dryness of steam, it should be appreciated that the method and
30 apparatus are also suitable for measuring the dryness of any other multiphase fluid
flow.

ORIGINAL
1. A method of determining the phase compositions of a multiphase fluid flow in a
fluid line, comprising:
5 obtaining a vibration signal from the fluid flow using a vibration sensor comprising
a target disposed in the fluid flow which vibrates in response to fluid flow in the fluid
line;
analysing the vibration signal to determine a first energy parameter which is
related to the energy of the vibration signal within a first frequency band, and a second
10 energy parameter which is related to the energy of the vibration signal within a second
frequency band; and
determining a phase composition parameter relating to the phase compositions
of the fluid flow using the first and second energy parameters.
15 2. A method according to claim I, wherein the phase composition parameter is a
dryness parameter relating to the dryness of the fluid flow.
3. A method according to claim 1 or 2, further comprising mixing the fluid flow
upstream of the vibration sensor.
20
4. A method according to any preceding claim, wherein the vibration sensor
measures the vibration signal in the time domain.
5. A method according to claim 4, wherein analysing the vibration signal includes
25 transforming the vibration signal from the time domain to the frequency domain.
6. A method according to claim 5, wherein the vibration signal is transformed from
the time domain to the frequency domain using a fast Fourier transform (FFT).
30 7. A method according to any preceding claim, wherein the first energy parameter is
dependent on the flow velocity.
8. A method according to any preceding claim, wherein the second energy
parameter is dependent on the phase compositions of the fluid flow and the flow
35 velocity.
ORIGINAL
9. A method according to any preceding claim, wherein the first energy parameter is
the total energy of the vibration signal within the first frequency band andlor wherein
the second energy parameter is the total energy of the vibration signal within the
second frequency band.
5
10. A method according to any of claims 1-8, wherein the first energy parameter is
the amplitude of the peak frequency within the first frequency band andlor wherein the
second energy parameter is the amplitude of the peak frequency within the second
frequency band.
10
11. A method according to any preceding claim, wherein the first frequency band
andlor the second frequency band is predetermined.
12. A method according to any of claims 1-1 0, wherein analysing the vibration signal
15 includes defining the first frequency band about a first peak frequency andlor defining
the second frequency band about a second peak frequency.
13. A method according to any preceding claim, wherein the first frequency band
contains a first peak frequency andlor wherein the second frequency band contains a
20 second peak frequency.
14. A method according to any preceding claim, wherein the first frequency band is
at a lower frequency than the second frequency band.
25 15. A method according to any preceding claim, wherein determining a phase
composition parameter comprises accessing a database containing data correlating
first energy parameters and second energy parameters with phase composition
parameters.
30 16. A method according to any preceding claim, further comprising outputting the
phase composition parameter.
17. A method according to claim 16, wherein outputting the phase composition
parameter comprises displaying andlor transmitting the phase composition parameter.
ORIGINAL
18. A method according to any preceding claim, wherein the fluid flow is a steam
flow.
19. A method according to claim 1 and substantially as described herein.
5
20. An apparatus for determining the phase compositions of a multiphase fluid flow
flowing in a fluid line, comprising:
a vibration sensor comprising a target arranged to be disposed in the fluid flow
which vibrates in response to fluid flow in the fluid line for obtaining a vibration signal
10 from the fluid flow;
a vibration signal analysis unit for analysing the vibration signal to determine a
first energy parameter which is related to the energy of the vibration signal within a first
frequency band, and a second energy parameter which is related to the energy of the
vibration signal within a second frequency band; and
15 a phase composition determining unit for determining a phase composition
parameter relating to the phase compositions of the fluid flow using the first and second
energy parameters.
21. An apparatus according to claim 20, wherein the phase composition determining
20 unit is a dryness determining unit for determining a dryness parameter relating to the
dryness of the fluid flow.
22. An apparatus according to claim 20 or 21, further comprising a fluid mixer for
mixing the fluid flow upstream of the vibration sensor.
25
23. An apparatus according to any of claims 20-22, wherein the vibration sensor is
arranged to measure the vibration signal in the time domain.
24. An apparatus according to claim 23, wherein the vibration signal analysis unit is
30 arranged to transform the vibration signal from the time domain to the frequency
domain.
25. An apparatus according to claim 24, wherein the vibration signal analysis unit is
arranged to transform the vibration signal from the time domain to the frequency
35 domain using a fast Fourier transform (FFT).
ORIGINAL
26. An apparatus according to any of claims 20-25, wherein the first energy
parameter is dependent on the flow velocity.
27. An apparatus according to any of claims 20-26, wherein the second energy
5 parameter is dependent on the phase compositions of the fluid flow and the flow
velocity.
28. An apparatus according to any of claims 20-27, wherein the first energy
parameter is the total energy of the vibration signal within the first frequency band
10 and/or wherein the second energy parameter is the total energy of the vibration signal
within the second frequency band.
29. An apparatus according to any of claims 20-28, wherein the first energy
parameter is the amplitude of the peak frequency within the first frequency band and/or
15 wherein the second energy parameter is the amplitude of the peak frequency within the
second frequency band.
30. An apparatus according to any of claims 20-29, wherein the first frequency band
is predetermined and/or wherein the second frequency band is predetermined.
20
31. An apparatus according to any of claims 20-29, wherein the vibration signal
analysis unit is arranged to define the first frequency band about a first peak frequency
and/or wherein the vibration signal analysis unit is arranged to define the second
frequency band about a second peak frequency.
25
32. An apparatus according to any of claims 20-31, wherein the first frequency band
contains a first peak frequency andlor wherein the second frequency band contains a
second peak frequency.
30 33. An apparatus according to any of claims 20-32, wherein the first frequency band
is at a lower frequency than the second frequency band.
34. An apparatus according to any of claims 20-33, further comprising a database
containing data correlating first energy parameters and second energy parameters with
35 phase composition parameters; and
ORIGINAL
wherein the phase composition determining unit is arranged to access the
database so as to determine a phase composition parameter relating to the phase
composition of the fluid flow.
5 35. An apparatus according to any of claims 20-34, further comprising an outputting
unit for outputting the phase composition parameter.
36. An apparatus according to any of claims 20-35, wherein the outputting unit
comprises a display for displaying the phase composition parameter andlor a
10 transmitter for transmitting the phase composition parameter.
37. An apparatus according to any of claims 20-36, wherein the apparatus is
arranged to determine the phase compositions of a steam flow.
15 38. An apparatus according to any of claims 20-37, further comprising a length of
pipe having connectors at either end, wherein the target is disposed within the pipe.
39. An apparatus according to claim 38 when appended to claim 22, wherein the
mixer is disposed in front of the target.
20
40. An apparatus according to claim 38 or 39, wherein the distance between the
connectors is in accordance within a predetermined standard.
41. An apparatus according to any of claims 20-40, wherein the vibration sensor
25 further comprises an electrical converter for converting the vibration of the target into a
vibration signal.
42. An apparatus according to claim 41, wherein the electrical converter comprises a
piezoelectric transducer.
43. A steam system comprising an apparatus in accordance with any of claims 20-
42.
Dated this the 12th day of September 20 13.
(ASHISH K. SHARMA)
Of SUBRAMANIAM 86 ASSOCIATES
Attorneys for the Applicants