Technical Field

Example embodiments relate to apparatus and methods for cavitation validation.

Background to the Invention

Ultrasonic cleaning typically involves immersing an item to be cleaned in a tank of cleaning liquid, then directing ultrasonic pressure waves into the tank. The pressure waves produce micro-cavitation in the liquid, which has a cleaning effect at the surface of the item to be cleaned.

There is a problem in providing an effective clean without either damaging the surface which is being cleaned or delivering an un-even cleaning action when the dirt on the surface is not evenly distributed and/or is composed of different types of material. For example, in cleaning surgical instruments before sterilisation, there may be various types of biological material on the instruments which is extremely difficult to remove, in different sized clumps. For this type of cleaning application effective removal of dirt is important to enable the sterilisation process to be performed effectively.

This problem can be compounded if there is an uneven distribution of ultrasonic pressure waves across the whole surface of the item to be cleaned. Standing waves linked to tank geometry can lead to the ultrasound in some parts of the tank being ineffective, and in other parts of the tank being too aggressive so as to potentially cause damage to the surfaces being cleaned or deliver poor cleaning in other parts.

Another problem encountered when trying to provide an effective clean is verifying that the cleaning apparatus is functioning correctly during a cleaning operation, with sufficient ultrasonic energy being provided to ensure the effectiveness of the cleaning process. For example, if there is a failure, or drop-off in performance with the systems used to generate the ultrasonic pressure waves it may not become apparent until after the cleaning operation has finished, if at all.

One method assessing the strength of ultrasonic pressure waves in a tank involves placing pieces of aluminium foil in the tank while the ultrasonic pressure waves are being generated, and then examining the foil to identify the effects of cavitation process, for example after a fixed period of time. However, this process is not easily automated, and there are challenges in measuring the activity with sufficient precision and repeatability throughout the tank. Example embodiments aim to address one or more problems associated with the prior art, for example those problems set out above.

Summary of the Invention

A cavitation validation apparatus for use in determining the ultrasonic activity in the tank of an ultrasonic cleaning system, the apparatus comprising: a sensor; a filter; a memory; and a processor; wherein the sensor is arranged to generate an output in response to cavitation noise detected in the tank of an ultrasonic cleaning system and pass the output to the filter; wherein in response the filter is arranged to generate a cavitation noise signal; and wherein the processor is arranged to sample the cavitation noise signal to produce a plurality of cavitation noise samples, store the cavitation noise samples in the memory, and perform a statistical analysis of the cavitation noise samples in order to determine ultrasonic activity.

In this way, the cavitation validation apparatus is useful in determining not just an instantaneous representative determination of ultrasonic activity, rather a statistical analysis of samples over time and/or space can be performed in order to determine ultrasonic activity in in the tank of an ultrasonic cleaning system.

In one example, the processor is arranged to store the result of the statistical analysis in the memory.

In one example, the cavitation validation apparatus comprises a clock and/or calendar function. In one example, the processor is arranged to store the result of the statistical analysis in the memory alongside a time and/or a date at which the cavitation noise samples were stored, for example a time and/or a date derived from the clock and/or calendar function. In one example, the processor is arranged to store output of the statistical analysis in the memory. In one example, the processor is arranged to store the result of the statistical analysis in the memory alongside an identifier for the samples, such as an identifier of the ultrasonic cleaning system from which the samples were derived.

In one example, the memory comprises a removable component, for example a memory card. In one example, the cavitation validation apparatus comprises an interface for a removable memory, for example a USB memory interface. In one example, the cavitation validation apparatus comprises an interface for a removable memory, for example a memory card slot. In one example, the memory is associated with an external device, for example an external data logging or data processing device, e.g. a computer. In one example the cavitation validation apparatus comprises an interface for a computer, for example a USB interface. In one example, the cavitation validation interface comprises an interface for a computer that includes a data cable.

In one example, the processor is arranged to sample the cavitation noise signal and store the cavitation noise samples according to a predetermined measurement regime.

In one example, the processor is arranged to sample the cavitation noise signal according to a predetermined measurement regime to produce sets of samples obtained in separate time windows, for example time windows of fixed and/or common duration between one another.

In one example, the cavitation validation apparatus comprises a depth indicator, to indicate a first measurement depth. In one example, the cavitation validation apparatus comprises a plurality of depth indicators indicating a corresponding plurality of measurement depths. In one example, the cavitation validation apparatus comprises three depth indicators. In one example, the cavitation validation apparatus comprises one or more depth indicators provided in fixed position relative to the sensor, for example attached to the sensor. In one example the sensor is attached to a probe, and one or more depth indicators are provided on the probe. In one example the sensor comprises a hydrophone.

In one example, the cavitation validation apparatus comprises a measurement cycle start control. In one example, the measurement cycle start control comprises a start button. In one example, the start button is provided in fixed position relative to the hydrophone, for example attached to the hydrophone. In one example, the hydrophone is attached to a probe and the measurement cycle start control is attached to the probe.

In one example, the cavitation validation apparatus comprises a measurement cycle indicator, operable by the processor to indicate the start and/or finish of a measurement cycle. In one example, the measurement cycle indicator comprises an audio output unit. In one example, the measurement cycle indicator comprises a visual output unit. In one example, the measurement cycle indicator comprises a traffic light arrangement, operable to indicate the start and end of a measurement cycle. In one example, the measurement cycle indicator is arranged to generate a stop indicator, to indicate that a measurement cycle is not in operation. In one example, the measurement indicator is arranged to generate a go indicator, to indicate that a measurement cycle is in operation. In one example, the measurement cycle indicator is arranged to generate a get-ready indicator, to indicate a measurement cycle is about to commence. In one example the measurement cycle indicator comprises a buzzer. In one example, the measurement cycle indicator comprises one or more LEDs.

In one example, the cavitation validation apparatus comprises a display. In one example, the processor is arranged to generate an instantaneous output indicative of the measured ultrasonic activity and to pass the instantaneous output to the display. In one example, the display is operable by the processor to show the instantaneous output. In one example, the display is operable by the processor to show the operational status of the apparatus, according to a predetermined measurement regime. In one example, the display comprises an LCD.

In one example, the processor is arranged to take an average of a plurality of samples to produce a set of aggregated data points. In one example, the processor is arranged to store and analyse the samples as raw samples. In one example, the processor is arranged to store and analyse the samples as aggregated data points. In one example, the processor is arranged to take a plurality of samples within 1 second. In one example, the processor is arranged to sample at greater than 5 samples/second, for example at 10 samples/second. In one example, the processor is arranged to aggregate samples every second, or for example within a 20 second measurement window. In one example, the processor is arranged to perform the statistical analysis on the samples as represented by the aggregated data points, such that reference to sample values and the like corresponds to the values of the aggregated data points.

In one example, the processor is arranged to perform the statistical analysis to generate one or more of: a maximum sample value; a minimum sample value; a spread value corresponding to the difference between maximum and minimum sample values; a mean value corresponding to the arithmetic mean of the sample values; a standard deviation of the sample values; a coefficient of variation corresponding to the ratio of the standard deviation relative to the mean; a number of samples below the mean; a number of samples above the mean. The generated outputs, in particular the mean value, enable ongoing measurement, for example by comparing samples generated at one time to be compared to samples generated at another. In healthcare this is relevant to validation of stability in operation of the apparatus, and analysis with thus be useful in determining transducer degradation or the like, which up to this point has not been observable or measurable in a convenient or reliable manner.

In one example, the processor is arranged to reference a predetermined safety zone value stored in the memory, above which the effect of the ultrasonic activity is determined to be sufficient for an intended cleaning operation. In one example, the processor is arranged to perform the statistical analysis to generate: a number of samples above the safety zone value; and a number of samples below the safety zone value. In one example, the processor is arranged to perform the statistical analysis according to a predetermined measurement regime, in a plurality of time windows. In one example, the processor is arranged to repeat the statistical analysis for samples obtained in a plurality of time windows, according to a predetermined measurement regime. In one example, the time window(s) are of predetermined duration, for example of equal duration as between measurements. In one example, the time windows are greater than 5 seconds, such as greater than 10 seconds. In one example, the time windows are less than 60 seconds, for example less than 40 seconds. In one example, the time windows are 20 seconds.

In one example, the processor is arranged to perform the statistical analysis three times, once in each of three separate time windows. In one example, the time windows are of a duration that is determined to enable the sensor to be moved through a tank volume. In one example, the time windows are of a duration that is determined to enable the sensor to be moved through a tank volume at a single predetermined depth. In one example, the processor is arranged to repeat the statistical analysis for samples obtained in a plurality of time windows, according to a predetermined measurement regime that involves moving the sensor through a tank volume at different depths, for example at one of two depths, or three depths, or more. In one example, the predetermined measurement regime involves a plurality of time windows, for one or more measurements at a first depth, and one or more measurements at a second depth.

In one example, the processor is arranged to compare the statistical analysis of different measurement instances on a periodic basis, for example twice or more, on a daily, weekly, fortnightly or monthly basis, and compare the outcome of the statistical analysis performed at different times compared to validate cavitation performance over time.

A cavitation validation method for determining the ultrasonic activity in the tank of an ultrasonic cleaning system, the method comprising: generating a sensor output in response to cavitation noise detected in the tank of an ultrasonic cleaning system; filtering the sensor output to generate a cavitation noise signal; sampling the cavitation noise signal to produce a plurality of cavitation noise samples; storing the cavitation noise samples in a memory; and performing a statistical analysis of the cavitation noise samples in order to determine ultrasonic activity.

In one example, the method comprises storing the result of the statistical analysis in the memory. In one example, the method comprises storing the result of the statistical analysis in the memory alongside a time and/or a date at which the cavitation noise samples were stored. In one example, the method comprises storing the result of the statistical analysis in the memory alongside an identifier for the samples, such as an identifier of the ultrasonic cleaning system from which the samples were derived.

In one example, the method comprises storing the samples and/or result of the statistical analysis in a removable memory component, for example a memory card. In one example, the method comprises storing the samples and/or result of the statistical analysis in an external device, for example an external data logging or data processing device such as a computer.

In one example, the method comprises sampling the cavitation noise signal and storing the cavitation noise samples according to a predetermined measurement regime.

In one example, the method comprises sampling the cavitation noise signal according to a predetermined measurement regime to produce sets of samples obtained in separate time windows, for example time windows of fixed and/or common duration between one another.

In one example, the method comprises arranging the sensor at a predetermined depth, for example by aligning a depth indicator with a liquid surface, to indicate a first measurement depth. In one example, the method comprises sampling the cavitation noise signal according to a predetermined measurement regime to produce sets of samples obtained at different predetermined depths, for example a different depth in each time window.

In one example, the method comprises operating a measurement cycle start control. In one example, the method comprises operating a start button. In one example, the method comprises operating a start button provided in fixed position relative to the sensor, for example attached to the sensor. In one example, the method comprises operating a measurement cycle start control on a probe that is attached to the sensor.

In one example, the method comprises indicating indicate the start and/or finish of a measurement cycle. In one example, the method comprises providing an audio output to indicate the start/and or finish of a measurement cycle. In one example, the method comprises providing a visual output to indicate the start/and or finish of a measurement cycle. In one example, the method comprises operating a measurement cycle indicatorthat comprises a traffic light arrangement, to indicate the start and end of a measurement cycle. In one example, the method comprises operating a measurement cycle indicator that comprises a traffic light arrangement to generate a stop indicator, to indicate that a measurement cycle is not in operation. In one example, the method comprises operating a measurement cycle indicator that comprises a traffic light arrangement measurement to generate a go indicator, to indicate that a measurement cycle is in operation. In one example, the method comprises operating a measurement cycle indicator that comprises a traffic light arrangement to generate a get-ready indicator, to indicate a measurement cycle is about to commence.

In one example, the method comprises generating an instantaneous output indicative of the measured ultrasonic activity and outputting the same. In one example, the method comprises showing the operational status of the apparatus, according to a predetermined measurement regime.

In one example, the method comprises taking an average of a plurality of samples to produce a set of aggregated data points. In one example, the method comprises storing and analysing the samples as raw samples. In one example, the method comprises storing and analysing the samples as aggregated data points. In one example, the processor is arranged to take a plurality of samples within 1 second. In one example, the processor is arranged to sample at greater than 5 samples/second, for example at 10 samples/second. In one example, the processor is arranged to aggregate samples every second, or for example within a 20 second measurement window. In one example, the method comprises performing statistical analysis on the samples as represented by the aggregated data points, such that reference to sample values and the like corresponds to the values of the aggregated data points.

In one example, the method comprises performing the statistical analysis to generate one or more of: a maximum sample value; a minimum sample value; a spread value corresponding to the difference between maximum and minimum sample values; a mean value corresponding to the arithmetic mean of the sample values; a standard deviation of the sample values; a coefficient of variation corresponding to the ratio of the standard deviation relative to the mean; a number of samples below the mean; a number of samples above the mean.

In one example, the method comprises storing a predetermined safety zone value stored, above which the effect of the ultrasonic activity is determined to be sufficient for an intended cleaning operation. In one example, the method comprises performing the statistical analysis to generate: a number of samples above the safety zone value; and a number of samples below the safety zone value.

In one example, the method comprises performing the statistical analysis according to a predetermined measurement regime, in a plurality of time windows. In one example, the method comprises repeating the statistical analysis for samples obtained in a plurality of time windows, according to a predetermined measurement regime. In one example, the time window(s) are of predetermined duration, for example of equal duration as between measurements. In one example, the time windows are greater than 5 seconds, such as greater than 10 seconds. In one example, the time windows are less than 60 seconds, for example less than 40 seconds. In one example, the time windows are 20 seconds.

In one example, the method comprises performing the statistical analysis three times, once in each of three separate time windows. In one example, the time windows are of a duration that is determined to enable the sensor to be moved through a tank volume. In one example, the time windows are of a duration that is determined to enable the sensor to be moved through a tank volume at a single predetermined depth. In one example, the method comprises repeating the statistical analysis for samples obtained in a plurality of time windows, according to a predetermined measurement regime that involves moving the sensor through a tank volume at different depths, for example at one of two depths, or three depths, or more. In one example, the method comprises performing a predetermined measurement regime that involves a plurality of time windows, for one or more measurements at a first depth, and one or more measurements at a second depth. In one example, the method comprises performing the statistical analysis nine times, once in each of three separate time windows for each of three different measurement depths.

In one example, the method is performed on a periodic basis, for example twice or more, on a daily, weekly, fortnightly or monthly basis, and the outcome of the statistical analysis at different times compared to validate cavitation performance over time.

In one example, the method is performed using the apparatus as set out above.

Brief Introduction to the Drawings

For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings in which:

Figure 1 shows a cavitation validation apparatus in use with an ultrasonic cleaning apparatus and a computer;

Figure 2 shown a schematic block diagram of the cavitation validation apparatus of Figure 1 ; and

Figure 3 shows example data from a cavitation validation operation.

Description of Example Embodiments Referring now to Figure 1 there is shown a cavitation validation apparatus 100. In Figure 1 , the cavitation validation apparatus 100 is shown in use, determining the ultrasonic activity in the tank 201 of an ultrasonic cleaning system 200, and providing data to a computer 300.

The cavitation validation apparatus 100 comprises a sensor 101 that is received in a probe 102. The probe 102 has three depth markers 103, and is detachably coupled to a connecting cable 106 by a connector 104. The probe also comprises a start button 105.

The connecting cable 106 is attached to the body 107 of the cavitation validation apparatus 100. Within the body 107 of the cavitation validation apparatus 100 are various electronic components as discussed in more detail with reference to Figure 2. Externally visible on the body 107 of the cavitation validation apparatus 100 are a graphic LCD display 108, a memory card slot 109, LED indicators 110; a sound signalling device 111 and a data cable 1 12 for connecting to the computer 300.

The ultrasonic cleaning system 200 further comprises cleaning solution 204 in the tank 201 and an ultrasonic transducer 202 for generating cavitation bubbles 203 in the cleaning solution.

To use the cavitation validation apparatus 100 carry out the measurements that validate the level of cavitation in the cleaning solution 204 of the ultrasonic cleaning system 200, the probe 102 is placed in the tank 201 such that the sensor 101 is located at a predetermined depth. Vibrations generated by the ultrasonic transducer 202 create gradient pressure within the cleaning solution 204 in the tank 201 , which results in cavitation bubbles 203 in the low- pressure areas. Such bubbles grow until they hit the high-pressure region, and then collapse, generating shock waves and other acoustic disturbances. The ensemble of cavitation bubbles generates a generally complex acoustic signal called cavitation noise. By filtering this noise and storing a statistical analysis of samples of the cavitation noise, the cavitation validation apparatus 100 is useful in determining not just an instantaneous representative determination of ultrasonic activity. Validation of the effective generation cavitation bubbles, and therefore the associated cleaning effect can be determined readily, throughout the volume of the tank 201 and the data stored to enable subsequent comparisons and checks to take place.

Figure 2 shown a schematic block diagram of the cavitation validation apparatus 100 of Figure 1 , connected to a computer 300 in the form of a PC. The probe 102 incorporating the sensor is shown, with the connector 104 and associated start button 105. The start button is connected directly to a processor 116. The output of the sensor is fed from the probe to an impedance matching amplifier 112, then through a filter 113 to select representative frequencies corresponding to cavitation noise. An RMS unit 114 performs initial smoothing, then an AC/DC converter 115 performs analogue-to-digital conversion before passing digital values to the processor 116 as samples.

Also shown is the SD card 109 that operates as a memory accessible to the processor 116, and the user interface components in the form of the LCD display 108, LEDs 110 and buzzer 1 11.

In use, a signal from the sensor 101 is fed from the probe 102 through the connector 104 to the impedance matching amplifier 112. The connector is suitably a BNC type. The impedance matching amplifier 112 matches the impedance of the sensor 102 with the input impedance of the filter 113.

Then, the amplified signal goes to the filter 113, which selects components of the cavitation noise spectrum, reflecting the level of cavitation activity. Next this signal is converted by RMS converter 114 into a DC voltage proportional to the rms value of the noise. Through the AC/DC converter 115 a digital signal is fed to the processor 116. The processor 116 is provided in the form of a microcontroller that controls the timing and the number of measurements, records the results on the SD-card 109 memory, or interfaces with a program on the personal computer 300 via a USB interface. Further the processor 116 is arranged to display information on the LCD display 108, and to control operation of the LED indicator 110 and buzzer 1 11.

A control button 105 is built into the handle of the sensor, so that the operator can readily control the start of a measurement operation, without needing to manipulate controls on the body 107 of the cavitation validation apparatus.

The cavitation validation apparatus 100 is equipped with a program of processing data, to perform a statistical analysis of the results received. This allows a user to record data of the cavitation activity and simultaneously display them on a computer monitor in a real time. The measurement results are saved in the form of graphs and tables as separate files automatically based on the storage algorithm selected by the operator. Range switching during data recording is performed automatically or manually. In addition to instantaneous plotting, the processor is programmed to perform statistical processing of data, namely: it calculates the average value during the registration, the maximum and minimum values, the spread of values in one measurement cycle, the number of points below and above the mean value, and the number of points that are below and correspondingly above a predetermined threshold referred to as a safety zone. In this way, ongoing verification of the proper operation of an ultrasonic cleaning system can be determined as a shift in the mean or an increase in out of range measurements can be detected when comparing a current set of measurements with those taken previously. The CVD is designed to measure at three depth levels, and to take three sets of measurements per level. Duration of data collecting of a single measurement is chosen to be 20 seconds, with a sample rate of 10Hz. The above statistics are calculated separately for each measurement, for each level and for all three levels together.

The program has the ability to store measurement data, graphs, and statistical information. Figure 3 shows example data from measurements taken at each of three depth levels.

It is possible to carry out measurements without connecting to a computer. In this case, the data will be written to the memory card.

Thanks to the new features, the results of the measurements characterize not only the level of cavitation activity, but also the degree of heterogeneity of the cavitation region in space and time.

Below is described an example of the measurement procedure for using cavitation validation apparatus 100, with either a memory card such as the SD card 109, or connected to a computer 300 or USB device.

MEASUREMENT PROCEDURE

If the memory card is inserted and the device is not connected to the computer, the measurement results are recorded on the card. If the instrument is connected to a computer via USB, the results are transferred to the computer.

Working with THE CARD

1 . Insert memory card.

2. Connect cable of the sensor output to plug IN.

3. Turn on the power switch.

4. The display will say “Level 1, Run 1 Press buton" and all LED indicators are off.

5. Place the hydrophone in the investigated ultrasonic field at level 1 .

6. Press the button on the sensor. On the display you will see “Level 1, Run 1 Get Ready”, yellow LED indicator will be on and short beep will sound. After 3 seconds short beep will sound, yellow LED will be off, green LED will be on and measurement will start automatically.

7. Scan the field of interest at level 1 with the sensor for 20 seconds.

8. After 20 seconds long beep will sound, green LED will be off, red LED will be on and measurement will stop automatically. 9. After 5 seconds red LED will be off and the display will show “Level 1, Run 2 Press button". The latter means that the apparatus is ready for the next run. The results of measurements will be saved in file “HHMMLXRY.TXT”, where HH is hour, MM is minute, X is level number and Y is run number.

10. Repeat steps 6 — 11 for runs 2 and 3. Then the display will show “Level 1, Run 3 Level 1 Done":

12. Repeat steps 6 - 11 for levels 2 and 3. Then for 5 seconds the display will show “Level 3, Run3 Level 3 Done" and after 5 seconds - “Level 1, Run 1 Press button". The latter means that 9 runs (3 runs for every level) are done.

13. Turn off the power switch.

Working with a program on the computer

1. Run the program “Measurement processing v4_mean_below.exe” or "Measurement processing v5_mean_above.exe".

2. Press the button OPEN FILES.

3. Select 9 files with Shift or Ctrl key.

4. Press the button OPEN.

The program will show you 3 timing diagrams and calculate max, min, mean, spread, STD, CV, N_below_mean, N_below_SZ (or N_above_mean, N_above_SZ) values of each reading and the same statistical values of all 3 readings.

Spread value is the difference between max and min values.

Mean value is the sum of the results of all measurements divided by the number of measurements.

STD is Standard Deviation.

CV is Standard Deviation relative to mean value.

N_below_mean (N_above_mean) is the number of points below (above) mean value. N_below_SZ (N_above_SZ) is the number of points that below (above) Safety Zone.

5. If you want to save calculated values to file, press the button SAVE STATISTIC and type desired file name. For example:

Data will be saved in text format.

WORKING WITH USB CONNECTION

1 . Connect USB cable to device and computer.

2. Turn on the power switch.

3. Press the button USB CONNECT.

4. If the date or time is wrong, press the button SET DATE AND TIME. Current date and time from your computer will be write to device automatically.

5. Press button on the sensor. On the display will be text “Level 1, Run 1 Get Ready” and yellow LED indicator will be on and short beep will sound. 6. After 3 seconds a short beep will sound, yellow LED will be off, green LED will be on and measurement will start automatically. You will see on the screen measured data, level number and run number in the program.

If checkbox “AutoSave Data” is set, data will be saved in directory with current data in file “HHMMLXRY.TXT”, where HH is hour, MM is minute, X is level number and Y is run number.

7. Make other measurements.

8. Save results.

9. Close the program.

10. Turn off the power switch.

11 . Disconnect USB cable.

Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.