Fibre-optic Hydrophone System: User Guide
Contents
1. EZO ELECTRIC MATERIALS ACOUSTIC SOURCES TEST TANKS 1 AUXILIARY PRODUCTS POWER MEASUREMENTS PASSIVE ACOUSTIC MATERIALS 1 P gt Fibre Optic Hydrophone System PRECISION ACOUSTICS CONTENTS Unpacking the Fibre optic hydrophone system ccccccsssecccesececeesececeesccecenececeeseceseueceseeecetsueeeesseecetseneeets 3 Paeka2e COM MIS ien aa aal ni E aiaiai aki T E kaa 3 Mae 00 EY TAN cape sc TE ma a eee 4 DS TN EO FV OI aema m oo oaniex outta ts olan 2 ec OO scenes 4 Overview of operating principles MS RAA ATU 4 Randine the SENSO MAA m amm mmm acshdeetnuteansacesetonssas neds skcceeenttseticeubedarecemsetase 4 INU CAE En e eects cat recta E alla osama E E E nti ca eaten TEDA AA 4 SOP OWall US eilicl tl Ol ereenn e EE EEEE EEN EE EEEN EEA 5 Connecting to an oscilloScCOpe esssssessssressrressrressrrresrreessrrossrrsserressrerssreessrerssreessterssreeserersstersereessreesererese 6 Connecting a sensor downlead s sissssisssserseresseronsursssunerouriosersnononssstskotoos usso aal aaa aa 6 Mounting the hydrophone cccccesccccessecccensccccesececeeseceeeuscceeeececeesececeueceseeeecessuaecessueeeseuecetsenecetseeeetees 6 OP FIO ext e aa a a s i 0 0 0 ise 7 WE NSA Oe a E 7 ST MEN ODNO Memm E a 10 lde E MEMM EE ETE E A TTE AA AE E E 11 Frequency Response Freq Response ccccccccesssecccceeesecccceeeseccceceesecceeeeuecceeeeeeeceeseeuneeeessueeeseetsaees2. This is a self extracting executable which will copy the necessary installation files to the PC and then install the system software Follow the on screen instructions to install the necessary National Instruments components Finally restart the PC when instructed to do so a On some PCs it may be necessary to unplug the hydrophone system for the PC to boot normally if this is the case a system disc error will be displayed asking you to remove the non system disc and press any key to continue If you receive this message simply unplug the hydrophone system and press any key on the keyboard The system is now installed and ready for use To run the control program go to Start gt All Programs gt FOH Control gt FOH Control A desktop shortcut will also be created for your convenience Precision Acoustics Ltd Hampton Farm Business Park Higher Bockhampton Dorchester Dorset DT2 80H UK t 44 0 1305 264669 e pa acoustics co uk www acoustics co uk gt Fibre Optic Hydrophone System PRECISION ACOUSTICS CONNECTING TO AN OSCILLOSCOPE In order to make acoustic measurements the hydrophone system must be connected to an oscilloscope via the AC out connector on the front panel The system is designed to have an output impedance of 50 Ohm thus an oscilloscope with a 50 Ohm input is reguired If your oscilloscope does not have this facility an inline terminator should be used Note Thermal measurement is made
3. mV MPa 8 1 4 6 8 0 12 f MHz S mV MPa U m 0 00 al sarm To enter freguency response data for a new sensor click New in the bottom right of the display This will open a data entry window where you can either load data from a file or add new data manually Note this feature is not yet implemented in the software and will be added at a later date Precision Acoustics Ltd Hampton Farm Business Park Higher Bockhampton Dorchester Dorset DT2 80H UK t 44 0 1305 264669 e pa acoustics co uk www acoustics co uk gt Fibre Optic Hydrophone System PRECISION ACOUSTICS TEMPERATURE MEASUREMENT TEMPERATURE Click Temperature in the main control set to start a temperature measurement task The temperature measurement begins the moment the Temperature control is clicked Data is recorded at a rate of 200 samples per second and streamed directly to disk However only 60 seconds of the recorded data is ever displayed on the screen once t gt 60 s the display will roll maintaining the most recent 60s worth of data only At the end of a measurement click Save to convert the temporary stored data to a tab delimited text file for use in your choice of data display manipulation software A dialogue will appear asking for confirmation of filename and directory A comment can also be added to the saved data At any time the measurement can be stopped for closer inspection
4. 12 Temperature measurement Temperature ccccccccssseccccceseeccecceseccceeeesecceeeueecssseueeeceeseeneeeessugeesss 13 Changing the SCNSOP cccccceesecccesscccceseccccesececeeccceeececsuseceeeusceeeeueceeeuececsuscceseuecesseecetsueeeeseeecetsenecets 14 WOES IOC AM A a 15 Visibie lieht source fault checking srren 2 feaeiuectananteedeare 15 a jeaiia lt 3 110 4114414 0 0se AM i E E 15 Check the hydrophone tip wiccscidivceseedcccsasassscdnscanecseasdensoavaccsscnebasderababanccbasssesevtadebsvasadtdsdsecesenepabamannaetes 15 Check fOr DENG Soesi annaa Eaa a E TA E AUE A mia 15 Check for DT CANS AAA SAS AASA TA ami 16 Verify the Interferometer Transfer function cccccceseccccsececeseccceececsesececeuscceseneceeeueceseuecessenecesseneeeeegecs 16 ld a Oo pestle tan enh 2 A T A me nonanenen E O 17 APPLICATIONS ADVICE AND TECHNICAL ASSISTANCE otsi t stsid aavaaa visata ad s aetesibi ii innaajal napi alaalia ale 17 Precision Acoustics Ltd Hampton Farm Business Park Higher Bockhampton Dorchester Dorset DT2 80H UK t 44 0 1305 264669 e pa acoustics co uk www acoustics co uk PACKAGE CONTENTS 2 1 PP TT Fibre optic Hydrophone System control unit Fibre optic hydrophone mount Two fibre optic hydrophone sensors minimum USB A B system connection lead IEC mains power lead Cletop S fibre optic connector cleaner cassette HUX Cleaner in adapter connector clea
5. NOT insert anything other than a fibre connector into the adaptor If the connector is dropped into water or gets wet allow to dry thoroughly and then use one of the supplied emergency optical wipes to clean the connector ferrule thoroughly Allow to dry again and then use the Cletop S cleaner prior to connecting the sensor to the system Precision Acoustics Ltd Hampton Farm Business Park Higher Bockhampton Dorchester Dorset DT2 80H UK t 44 0 1305 264669 e pa acoustics co uk www acoustics co uk gt Fibre Optic Hydrophone System PRECISION ACOUSTICS MOUNTING THE HYDROPHONE The fibre optic hydrophone system is supplied with a removable mount compatible with Precision Acoustics Ltd needle hydrophone mounts To load the hydrophone into the mount first detach the cone section from the shaft of the mount then thread the fibre through the shaft Remove the protective sleeve from the tip of the hydrophone and very carefully thread the tip through the cone sectionn Screw the shaft section back onto the cone just tight enough for the fibre to be gripped DO NOT OVER TIGHTEN THE SHAFT doing so may damage the hydrophone Similarly over tightening with no fibre installed will damage the cone section OPERATION INITIALISATION Once the system is switched on set up as described in the previous section and connected to a PC the control software should be loaded by double clicking the desktop shortcut or locating the item on
6. light source can be used to verify this ATTACH THE VISIBLE LIGHT SOURCE ad Pa PI A 1 fa A pe a ESTERS A PM F A A gt 5 aneeaeaueeee Pe aacr tpr SaSeaeeee er re Once the visible light source is connected to the hydrophone and switched on a red glow will be visible both at the tip of the fibre and where at the connector end This is normal CHECK THE HYDROPHONE TIP An undamaged hydrophone tip will glow slightly with the red light from the visible source If the tip has been damaged significantly more light will be visible leaving the hydrophone tip CHECK FOR BENDS A bend in the fibre causes light to escape All bends should be avoided but the tighter the bend the more light is lost and the higher the risk of breaking the fibre gt Fibre Optic Hydrophone System PRECISION ACOUSTICS CHECK FOR BREAKS If the fibre is bent too far it will snap internally In this case all of the light will escape and a bright point of light will be seen through the yellow jacket VERIFY THE INTERFEROMETER TRANSFER FUNCTION The interferometer transfer function of each sensor supplied with the system can be found on the hydrophone system at T Data ITFs where T is the drive letter associated with the fibre optic hydrophone system labeled FOH System in My Computer The data is saved in tab delimited text files and can be viewed in Excel or other such p
7. manually tuned using the Channel up and down arrows This feature may be useful if looking at highly non linear fields enabling the linear range of the sensor to be shifted towards higher peak positive pressures For further information on the use of this function contact Precision Acoustics Ltd Clicking Save in the bottom right of this display will save the current ITF to disk A dialogue box will pop up asking for a filename and directory to which to save the ITF Precision Acoustics Ltd Hampton Farm Business Park Higher Bockhampton Dorchester Dorset DT2 80H UK t 44 0 1305 264669 e pa acoustics co uk www acoustics co uk gt Fibre Optic Hydrophone System PRECISION ACOUSTICS FREQUENCY RESPONSE FREQ RESPONSE Clicking Freq Response shows the frequency response of the hydrophone selected from the drop down menu Sensor Frequency response data for the sensors supplied with the system are stored on the system itself To display the sensitivity of the selected sensor at a particular frequency enter the desired frequency in the control below the graph f MHz The sensitivity in mV MPa and the uncertainty in percent are then displayed alongside If a value of frequency greater than the maximum calibration frequency is entered the display will only show the sensitivity at the maximum frequency Fibre optic Hydrophone Syster pa Fibre optic Hydrophone System ISON ACOUSTICS LD TERRE Sensitivity
8. the Start menu This will initialize the system and bring up the following window Precision Acoustics Ltd Hampton Farm Business Park Higher Bockhampton Dorchester Dorset DT2 80H UK t 44 0 1305 264669 e pa acoustics co uk www acoustics co uk gt Fibre Optic Hydrophone System PRECISION ACOUSTICS Fibre optic Hydrophone System File Help Pi ON Fibre optic Hydrophone System RECISION ACOUSTICS LTD The first time the software is run after the system has been switched on the initialization may take up to 30 seconds as the laser warms up Once the initialization is complete the Status indicator will turn green and the following page will be displayed Precision Acoustics Ltd Hampton Farm Business Park Higher Bockhampton Dorchester Dorset DT2 80H UK t 44 0 1305 264669 e pa acoustics co uk www acoustics co uk gt Fibre Optic Hydrophone System CISION ACOUSTICS ON Fibre optic Hydrophone System CISON ACOUSTICS ID Wekome to the Precision Acoustics Fibre optic Hydrophone System control software To begin using the system ensure a fibre sensor is connected and dick Begin Precision Acoustics Ltd Hampton Farm Business Park Higher Bockhampton Dorchester Dorset DT2 80H UK t 44 0 1305 264669 e pa acoustics co uk www acoustics co uk gt Fibre Optic Hydrophone System PRECISION ACOUSTICS USING THE HYDROPHONE To make an acoustic measurement with the system ensure a sensor
9. MS Windows Minimum XP Switch on the system power switch on rear panel if this is the first time the system has been plugged into the PC the following may appear Found New Hardware Wizard Welcome to the Found New Hardware Wizard This wizard helps you install software for USB Serial Port IF your hardware came with an installation CD SSE or floppy disk insert it now What do vou want the wizard to do Install the software automatically Recommended Install from a list or specific location Advanced Click Next to continue Cancel Click Next and follow the onscreen instructions If other similar windows pop up run through these also a If any of the hardware installations fail at this point don t worry just carry on with the rest of the installation Navigate to My Computer and double click on the drive named FOH_System the drive letter will be system dependent 7 My Computer File Edit view Favorites Tools Help Q Bach wi Je Search ar Folders ek A Folder Sync 4 My Computer v 3 gt System Tasks H SPVA P Local Disk S lt g Local Disk D Coe 11177 002_009 E CD ROM SP data on pa s1 G lt FOH System T View system information To Add or remove programs G Change a setting Other Places My Network Places E My Documents A a t 1 Double click on FOH 1 X X X Installer exe
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11. bythe software thus no additional connection is reguired for this function CONNECTING A SENSOR DOWNLEAD Before using the system a sensor downlead must be connected to the adaptor on the front panel To do this remove the dust cap from the adaptor on the front panel and the connector on the sensor downlead Using the supplied Cletop S cleaning cassette clean the tip of the fibre connector by sgueezing the handle and swiping the face of the connector across each of the exposed tape strips and then carefully insert the connector into the adaptor ensuring the key on the connector lines up with the notch on the adaptor The connection to the downlead is optical Thus it is vitally important that both the connector end face and the adaptor remain clean Any contamination of the interface between the sensor downlead and the system will lead to degradation of the acoustic sensitivity of the system Please adhere to the following guidelines to ensure optimum performance of the hydrophone system e Clean the sensor connector prior to EVERY use o Even if the sensor is only temporarily removed from the system clean it again before it is re inserted e Avoid contamination of the connector o Always apply the dust cap when the sensor is not attached to the system o DO NOT allow the connector to get wet or submersed in water e Avoid contamination of the adaptor o When the system is not in use the adaptor dust cap should be attached at all times o DO
12. ch channel the laser is currently operating at Below the status indicator are the main system controls e Re bias Acquire the interferometer transfer function and optimize sensitivity Precision Acoustics Ltd Hampton Farm Business Park Higher Bockhampton Dorchester Dorset DT2 80H UK t 44 0 1305 264669 e pa acoustics co uk www acoustics co uk gt Fibre Optic Hydrophone System PRECISION ACOUSTICS e ITF Showthe last acquired interferometer transfer function e Freq Response Show sensor frequency response e Temperature Begin temperature measurement acquisition e End End current measurement task and enter idle state laser off Which controls are visible depends on the current status of the hydrophone system ITF DISPLAY Clicking on ITF in the main system controls causes the system to show the interferometer transfer function The software display will change to the following Pp Fibre optic Hydrophone Systen Dt Fibre optic Hydrophone System Interferometer Transfer Function 1 2 ti i i i i i i i i i i i i H 1 70 80 90 100 110 120 130 140 150 160 170 180 190 200 Laser Channel Ha m ITF displayed in graph is representative of a typical ITF however they do vary From the ITF display it is possible to disable the automatic tracking of the bias point This is not generally recommended However when tracking is disabled the laser can be
13. d in the sensor downlead comprises a thin glass fibre OD 125 um surrounded with a thin acrylate primary buffer layer OD 250 um and encased in a flexible plastic jacket OD 900 um Optical fibre is very flexible in nature however it is important to remember that the light carrying part of the fibre is made of glass and careful handling is important to ensure the longevity of the sensor downlead If the glass fibre is broken light will no longer reach the sensing element and measurements will be impossible In particular when handling the fibre downlead the following guidelines should be observed e Avoid tight bends in the fibre to prevent sensor damage o Bend radii less than 10 mm should be avoided e Avoid knotting the fibre o Tangles and knots in the fibre should be careful undone without pulling the fibre taut e When in use ensure the fibre is kept clear of mechanical equipment such as translation stages etc so that it does not become entangled in moving parts INSTALLATION Precision Acoustics Ltd Hampton Farm Business Park Higher Bockhampton Dorchester Dorset DT2 80H UK t 44 0 1305 264669 e pa acoustics co uk www acoustics co uk gt Fibre Optic Hydrophone System PRECISION ACOUSTICS SOFTWARE INSTALLATION oe i Connect the IEC mains inlet to the rear of the system and a mains socket Connect the USB cable to the front of the system and to a spare USB socket on your PC Ensure PC is switched on and running
14. is connected to the system and click Begin The system will then bias the sensor ready for measurement This takes approximately 3 5 s during which time a progress bar will be displayed Once biased the system is active and in the presence of an ultrasound field the acoustic pressure wave is output from the AC out connector on the front panel The following screen is then displayed Pp Fibre optic Hydrophone Systen File Help Dt Fibre optic Hydrophone System Hydrophone system is now active Select from control on the right to re bias hydrophone show the ITF show the frequency response make a temperature measurement or end current measurement and return to idle state Tip Hover the mouse over controls and indicators for more information on their functionality Click the help icon to enable the context help window to get more information E Current system status is displayed here lael marana The status indicator in the top right of the screen shows e Status The current system status o Dark Green system is idle o Bright Green system is on and active o Amber system is on and monitoring but tracking is not active o Blinking yellow in combination with either bright green or Amber System is monitoring and recording temperature changes o Red an error has occurred e inverting If the acoustic signal is being inverted e Locked If the laser is locked to a channel e Channel Whi
15. ner Optional JIDSU Visual Fault Locator This instruction manual gt Fibre Optic Hydrophone System PRECISION ACOUSTICS INTRODUCTION The following document provides an outline for the installation and use of the Precision Acoustics Fibre optic Hydrophone System It is assumed that the reader has knowledge of making measurements with other hydrophone devices such as PVDF needle and membrane hydrophones Further information on making acoustic measurements with hydrophones can be found on our website http www acoustics co uk In addition Precision Acoustics Ltd offer training courses covering many aspects of acoustic measurement techniques and practices SAFETY INFORMATION OVERVIEW OF OPERATING PRINCIPLES The fibre optic hydrophone works on the principle of interferometric detection of changes in the optical thickness of a thin polymer film at the tip of the optical fibre sensor downlead Changes in the thickness may be induced acoustically through the acoustic pressure or thermally The system is capable of differentiating between the two and making simultaneous measurements of both A full description of the operating principles can be found in A Fabry Perot fibre optic ultrasonic hydrophone for the simultaneous measurement of temperature and acoustic pressure P Morris et al J Acous Soc Am Vol 125 6 pp 3611 3622 June 2009 HANDLING THE SENSOR The optical fibre use
16. of the acguired data for example and or reset Resetting will clear the temporary data store Pp Fibre optic Hydi ophone Systen File Help Dt Fibre optic Hydrophone System Temperature Measurement 0 5 1 1 l 0 0 20 40 60 80 100 12 0 140 16 0 18 0 20 0 22 0 240 Time 5 AUX IN The front panel of the hydrophone system includes a BNC connector labeled Aux in This is connected internally to an A D card enabling external analogue signals to be recorded alongside any temperature measurements This may be useful for the synchronization of temperature and pressure measurements if a gate signal is recorded to indicate the switching on off of the ultrasound field To enable disable the aux input click the Aux in switch at the top right of the graphic display SYNC OUT Precision Acoustics Ltd Hampton Farm Business Park Higher Bockhampton Dorchester Dorset DT2 80H UK t 44 0 1305 264669 e pa acoustics co uk www acoustics co uk gt Fibre Optic Hydrophone System PRECISION ACOUSTICS In addition to the Aux input the hydrophone system provides a Sync out signal from the front panel The sync output provides a square wave TTL signal with a low high switch occurring for each measurement point on the temperature time curve This signal is provided to facilitate the synchronous acquisition of acoustic waveforms and temperature rises It is important to note that there i
17. rograms If a damaged sensor is suspected but the visible light source check was inconclusive measure the ITF of the sensor by selecting Begin and then ITF and compare it to the file saved on the system The function may shift along the x axis as a result of temperature changes but the overall function shape should always remain the same Any significant change in shape will likely lead to inaccuracy in acoustic measurement Precision Acoustics Ltd Hampton Farm Business Park Higher Bockhampton Dorchester Dorset DT2 80H UK t 44 0 1305 264669 e pa acoustics co uk www acoustics co uk gt Fibre Optic Hydrophone System PRECISION ACOUSTICS WARRANTY Products are covered against defect of manufacturing or workmanship only Warranty period Fibre probes 6 months Control unit and accessories12 months If a warranty claim is made on devices that have been calibrated at NPL London a charge will be made for the used part of the calibration e g failure of fibre probe at 3 months charge for recalibration at NPL is 50 of calibration charge APPLICATIONS ADVICE AND TECHNICAL ASSISTANCE Further advice and technical assistance can be obtained from our Applications Engineers Tel 44 1305 264669 Fax 44 1305 260866 email technical acoustics co uk Precision Acoustics Ltd December 2011 V1 2 Precision Acoustics Ltd Hampton Farm Business Park Higher Bockhampton Dorchester Dorset DT2 80H UK t 44 0 1305 264669 e p
18. s a low high switch i e rising edge for each measurement point but that some measurement points are recorded by the system as not a number NaN This is to minimize the effect of artefacts in the temperature measurement arising from the tuning of the laser during temperature acquisition Synchronisation of temperature and pressure acquisitions is maintained by recording the time value of each measurement point pulse but recording NaN in the temperature measurement data when the measurement coincides with a laser tuning event To enable disable the sync output pulse click the Sync out switch at the top right of the graphic display CHANGING THE SENSOR If the sensor fails or is disconnected the system will typically detect this disable the laser inform the user and return to the initial display However if the user wishes to change the sensor or disable the laser output for any reason clicking the End button in the main controls will disable the laser and return to the software to the main screen The sensor can then be changed and a new measurement task started Precision Acoustics Ltd Hampton Farm Business Park Higher Bockhampton Dorchester Dorset DT2 80H UK t 44 0 1305 264669 e pa acoustics co uk www acoustics co uk VISIBLE LIGHT SOURCE FAULT CHECKING The hydrophone is optionally supplied with a visible light source for fault checking and to aid alignment If it is suspected that a sensor is broken the visible
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