Gamma-2 Abyss User`s Manual
Contents
1. Data After the Data heading lines of comma separated data will appear containing the parameters listed under ColumnHeadings for example 40324 6180722222 2 38790 0 1032 0 2018 22 83 e Time is expressed as the number days since the start of January 1 1900 which is the native format of Microsoft Excel The time of day including fractions of seconds is included in the fractional part of this number e Depth is in meters e cl and c2 are the calibrated attenuation coefficients at the two wavelengths of the Gamma 2 e IntT is the internal temperature of the Gamma 2 in C 6 4 Calibration Formulas The calibration formulas support compensation for several kinds of temperature and pressure related effects Depending on the characteristics of the individual instrument some portions of the processing may be turned off by setting the applicable coefficients to zero in the factory calibration file 6 4 1 Depth Offset adjusted pressure reading PT P F pL pT po where P is the raw pressure reading direct from the instrument in counts and the temperature related offset is P T k T k T Calibrated depth in meters of sea water D kp P T kp P T Y 21 6 4 2 where and Attenuation Transmission adjusted for temperature and pressure t T P 4 yee T ap P T is the instrument s internal temperature in C P is the temperature adjusted pressure reading P 7 in dig2. reflector TEO LEDs 1 2 Path Length k Fate not to scale Beam Splitter Reference Detector Figure 1 Optical Schematic As Note that ideal attenuation measurements require optics that completely reject all scattered light regardless of how small the scattering angle In practice all transmissometers have finite acceptance angles receive some scattered light and therefore report attenuation values smaller than the theoretical value Gamma 2 Abyss s optics are closer to the ideal than most transmissometers and therefore it will report somewhat higher attenuation values than those instruments 1 2 Mechanics The Gamma 2 Abyss achieves its extreme depth rating through the use of titanium for the housing and custom made sapphire windows The retroreflector is isolated from ambient pressure in its own housing with sapphire windows The path length is determined by the standoff that attaches the retroreflector housing to the main housing The standoff is machined in one piece to give it great strength and rigidity Figure 2 shows the instrument s outside dimensions 1 3 Electronics A powerful logging computer 128 MBytes more upon request of nonvolatile flash memory and integration with a companion battery pack section 4 allow the Gamma 2 Abyss to operate autonomously for deep profiling or long term sampling without real time electrical connections to the surface A high resolution multi channel
3. To restore the default settings send the commands SW 1 1 1 and LOG 0 To make the LOG settings permanent also send STORELOG 3 3 2 Sleep Wake Details In sleep mode all activity is suspended and current consumption falls to about 100 pA Sleep can be initiated either with the external switch or with the SLEEP command see section 5 2 11 During sleep all settings and state information are maintained in battery backed memory If a logging cast is in progress at the time of sleep it will resume upon the Figure 4 Switch location The arrows on the switch actuator Ithough if sl is tri th Next Wane although ar plep as Aereo Uy ihe point toward the start position switch by default the cast will be stopped first Sleep is ended by moving the switch to the start position by any activity on the serial port input or by the real time clock if a sleep time was specified with the SLEEP command If power is removed while it is asleep applying power again will only wake the instrument if the switch is in the start position see Switch Details below 3 3 3 Switch Details The behavior of the switch can be altered from the defaults described above with the SW firmware command also see section 5 2 15 SW can independently set whether the switch starts casts stops casts and puts the instrument to sleep However the switch will always wake the Gamma 2 from sleep Note that except at the time power is first applied the s
4. kTauP2 7 6957e 10 kTauP3 1 1615e 14 kTauP4 0 kTauP5 0 Tau0 1 00167 TPW 20 77 Attenuation 2 lt Same format as Attenuation 1 gt End cd Table 1 Parameters as Named in the Calibration File Term Name in Cal File Description kpi kp2 kp1 kp2 Coefficients for temperature related change in pressure offset Po PO Raw pressure reading at atmospheric pressure and temperature Tpo Tro TPO Temperature at which Py was measured kp Kp kD1 kD2 Coefficientss for conversion of digital counts to meters of sea water L L Path length in meters So SO Raw signal with path blocked Ro RO Raw reference with LED disabled kro krs kTO KT5 Transmission temperature coefficients P Po Pl P2 Pressure thresholds in temperature adjusted counts for ap P Es kTauPX Coefficient of linear pressure correction ap P leo kTauP0 kTouP Coefficientss for polynomial pressure correction in ap P kps 5 T Tau0 Temperature compensated transmission in pure water at atmospheric pressure Tpw TPW Temperature at which z measured 24
5. digital to analog converter sets the LED currents under the control of the computer allowing the current to be trimmed for optimum signal levels and balance between the wavelengths The currents to the LEDs are modulated and synchronized with the analog to digital conversions so that the signals from the LEDs can be digitally isolated from each other and processed separately even though they share detectors and preamplifier electronics All signals are digitized at 1000 samples per second and digital filtering is applied to minimize noise in the final outputs 11 7 cm BE Ma fl 10 2 cm diameter 1 2 Path Length 50 or 15 cm 11 9cm Figure 2 Outside Dimensions 2 QUICK START Setup Install HydroSoft on your computer HydroSoft 2 80 or later is required Connect the power data interface PDI cable to the appropriate RS 232 serial port on your computer or to a USB Serial adapter Connect the PDI s underwater connector to the Gamma 2 Abyss Run HydroSoft by selecting it on the Windows Start menu Click gt or select Connect from the Instrument Menu Click the Search button After a short time HydroSoft should identify the instrument load its calibration and close the Connect dialog box Select Set Date Time from the Gamma 2 menu Click Set Time to synchronize the Gamma 2 clock with your computer s clock This will take a few seconds Then click Close to cl
6. header is a complete record of every byte received from the instrument This will include data packets but may include other informational messages In the following example the START command sent by HydroSoft is echoed by the instrument which also announces the start and end of the cast START Starting cast 6 in 2 seconds 1274885398 44 1 2 0 0 5588 1938 2278 2325 1117 12511 23402 22826 22015 21489 504 1274885398 94 1 3 1 1 5601 1933 2273 2325 1117 12511 23404 22827 22014 21483 500 1274885401 94 0 1 1 0 5592 1936 2277 2326 1117 12513 23399 22794 22012 21487 500 Stopped cast 6 6 3 DAT File Format HydroSoft dat files start with a header similar to the following As with the raw header the exact contents and format are not guaranteed but the Channels and ColumnHeadings heading will remain the same The Channels heading announces the names of the primary optical data from the instrument as displayed in the legends of HydroSoft s graphs listed one per line The line following ColumnHeadings is a comma separated list ofthe names of the parameters listed in the data lines Header HydroSoftVersion 2 81 CreationDate 04 10 10 14 49 43 FileType dat DeviceType Gamma 2 DataSource Gamma 2 CalSource Gamma 2 Serial G2100100 20 Config 100 Channels c470 e532 ColumnHeadings Time Depth c470 c532 IntT
7. prevent hazardous buildup of gas that could result from rare faults in the batteries or charger Figure 7 Abyss Battery Pack The battery pack has a nominal voltage of 10 8 with the actual voltage ranging up to 13 V when fully charged depending on temperature HydroSoft displays the voltage whenever the instrument is connected and logging but remember that if voltage is being supplied by another source only the higher voltage is displayed The battery is roughly 90 discharged when its voltage declines to 10 V Its total capacity is 3 A hr enough to power the Gamma 2 continuously for well over 24 hours The output is protected against heavy Common 1 O 4 Charger overload by a positive temperature coefficient thermistor resettable fuse that reduces the O output voltage if the current goes above about di 3 Charger 3 A Once tripped the thermistor will keep the Figure 8 Battery pack connector current low but not zero until the load is wiring SubConn BH4F connector face view Mating connector is IL4M cool 14 disconnected long enough for the thermistor to 4 2 Charging Charge the pack only with the HOBI supplied charger Plug the charger into the battery pack before connecting the AC input to the charger and after disconnecting the AC input This prevents shorting the exposed pins on the charger s adapter cable while power is applied Do not charge the battery too frequently Note t
8. separate power sources to them Power will be drawn from the source that has the highest voltage 1 Common O v 2 l1 Common Transmit 4 OFO O O vs Receive 3 SubConn BH4M BH2M Figure 3 Connector pin diagrams face view of male connectors Power Data Interface PDI Cable The optional PDI cable connects to the 4 pin connector and provides 4 way binding posts for power and a DB9F for connection to a computer s RS232 port Data interface Commands and data are transmitted via RS232 8 bits no parity 1 stop bit The default baud rate is 57600 baud with standard rates from 2400 to 115200 supported In HydroSoft the baud rate can be changed from the Gamma 2 menu See section 5 for information about commands and Section 6 for data formats 3 2 Data Sampling and Logging Data are logged in flash memory according to parameters set with HydroSoft s Sampling Options command or with the LOG firmware command section 5 2 9 Data casts are started and ended either by software command or by the switch on the end cap Figure 4 Depending on the LOG and switch settings a data cast may also be started each time power is applied to the instrument During casts every sample saved in memory is simultaneously transmitted from the serial port Individual samples can also be requested with the D firmware command section 5 2 3 Samples requested this way are not logged Averaging and Packet Timing Gamma 2 col
9. 15 SW StartsCast StopsCast Sleeps Displays the current switch parameters and changes them if valid values are supplied Nonzero StartsCast means that moving the switch from off to on will start logging as if the START command were issued Nonzero StopsCast means moving the switch from on to off will stop logging as with STOP Nonzero Sleeps means moving the switch from off to on will put the instrument into an indefinite sleep as with the SLEEP command The default setting is 1 for all three parameters For more about the switch see section 3 2 5 2 16 VER Displays the installed firmware version 5 2 17 VIN Displays the input supply voltage to the instrument If voltages are applied to both connectors only the higher one is reported The voltage reported will be slightly lower than the actual applied to the connector because it is measured after the voltage passes through a protection diode This is the same voltage that is reported in full data packets FR 6 DATA PROCESSING REFERENCE 6 1 Data Formats Data are transmitted in raw comma separated decimal ASCII with the following parameters time signall signal2 referencel reference2 pressure temp1 temp2 temp3 Vin bgnd smin smax rmin rmax N e Time is in seconds since midnight Jan 1 1970 sometimes called UNIX time e Signall and signal2 are raw digital counts measured by the signal detector from the two optical channels e Referencel and Reference2 are
10. Gamma 2 Abyss Deep Sea Transmissometer USER S MANUAL Revision D HOBIL Abs Hydro Optics Biology amp Instrumentation LIGHTING THE WAY IN AQUATIC SCIENCE A N MIES www hobilabs com support hobilabs com Revisions D March 2011 Change Abyss 2 to Gamma 2 Abyss C November 2010 Correct calibration formulas section 6 4 2 B May 2010 Extensive revision and additions A May 2010 Initial Release L INTRODUCTION 0 isccseseccsisccisessectecscosssestesovssesccvacssessacsoeseseoesdesdevcesseceabssastectsonstessecssetcsescesstectessceosbiesesses 4 11 OPTOZELECTRONIGC DESIGN a so vo cnet Seek Suse a ere wash dean oka deveuaes AEN 4 12 MECHANICS a ei ha Ohad iaa ica ae 5 1 37 TEELECTRONTOS A EA EN A a ca ass 5 2 QUICK START hroir sxecsente vets sevec svuvscuces ssesshenessones ini ssoi Esis s enadsontedducesbedesbasceos cesvsesodecsdeses eees 6 ZO E ld ERASE ANI e tad Mr dd de A e AEEA 6 262 COLLECTING DAT Ac id da it aia EEE ias aL ads ALE daa I cis alzas 6 2 3 DOWNLOADING LOGGED DATA cccccceccccesssscecesssececesececcssceccessecccesseececseseceesueeccessecccsessesenseeeceesseess i 2 4 DISCONNECTING E A E E AT ERE 7 2 5 SWITCH ACTIVATED LOGGING csccsccsccessessesncecccossnsscecesccscessscoueescesceenscnececccesenseenceseessesssceeeeecescesse 7 3 OPERATIONAL DETAILS siscssccasesesceecasbsacece cose scvsnsonaveacesbanconesss cove ousecenseedcosbasoaneess cpobosedacevesvesoseons
11. cting e After you are finished communicating with the Gamma 2 select Disconnect from the Gamma 2 menu When asked Put Gamma 2 to sleep before disconnecting click Yes e Unplug the PDI cable from the Gamma 2 2 5 Switch Activated Logging Note that the switch behavior can be modified with firmware commands For details see section 3 3 e To start a cast when the Gamma 2 is asleep and disconnected from the computer move the switch on the end cap to the start position in the direction of the arrows on the switch actuator If the switch is already in the start position first move it briefly to the opposite position e To end a cast return the switch to the stop position 3 OPERATIONAL DETAILS 3 1 Power and Data Interface Power Supply The Gamma 2 requires a power source of 10 to 24 V at 1 to 1 5 W The exact power consumption depends somewhat on the choice of wavelengths since different LEDs have different efficiencies With 470 nm and 532 nm channels power is typically 1 2 to 1 3 W over the entire supply voltage range In sleep mode see section 3 3 current consumption is less than 100 yA at 12V Connectors Data and power connections are through a SubConn BH4M connector mating connector IL4F A BH2M connector mate IL2F provides a second power input Figure 3 shows the connector pin assignments The power inputs on the two connectors are identical and protected against reverse voltage so it is safe to connect
12. ecees 8 321 POWER AND DATA INTERPA CE otra tdi 8 3 2 UDATA SAMPLING AND LOGGING nissan tela cha cobet cade a bats cussneaet e ak EnA aeann 9 3 3 POWER UP SLEEP MODE AND SWITCH CONTROL cccccssccecesssssecesececsesseceeceecesensaeceeececeensaseeeeeecenees 9 3 4 DEPLOYMENT 4 abia be dens aa a aaee iia 11 325 CTERANING 90 and dto bad 13 4 BATTERY PACK AA TN 14 Ail DESCRIPTION it A e dia ti e 14 AD CHARGING E AE LA A A A ic eo es 15 5 FIRMWARE COMMANDS wisccscccsccasccescoscascceccosconsonscecesnsenscsesccecdcoscsonsecsesccdcbescnnseascacouosesesosccsesossnesvece 16 Dele PROTOCOL AUN Rt Dit Be Lae os 16 5 2 COMMON COMMANDS ccccccccccssssssecesececeessseececcesensesseeeececsesaseeecececeessaaeeeeccesesssaeeeeeceesenseseeseneeseneea 16 6 DATA PROCESSING REFEREN CRijs sssccs sccscsedessnccsceccessessestesscousassetossedssenavedsessedvessscsseboevessoosonedeesd 19 Gel DATA RORMATS 20 AA AAA ns 19 02 RAW BILE FORMA dd a deis 19 6 37 DATIETE FORMA EE EE REEN E atada 20 6 4 CALIBRATION FORMULAS ci tdci 21 6 93 CATIBRATION FILE FORMAT o ii ii ita tte 22 1 INTRODUCTION The Gamma 2 Abyss is a dual wavelength transmissometer that operates at ocean depths up to 6 000 meters It is part of the HOBI Labs Gamma family of spectral transmissometers which differ in depth ratings and number of wavelengths but share many features The Gammas use a folded optical path to keep all electronics in a single pressure housing and to supp
13. hat the charger replaces charge 10 to 20 times as fast as the Gamma 2 consumes it ls 5 FIRMWARE COMMANDS The Gamma 2 is configured and controlled with commands sent via its serial communication port When you use HydroSoft the commands needed for routine operation are generated automatically and you do not need to know the details However you can type commands manually and view the instrument s replies directly via HydroSoft s terminal window or a generic terminal program 5 1 Protocol The Gamma 2 communicates through a standard RS 232 serial connection with 8 data bits no parity one stop bit and no handshaking The default baud rate is 57600 but it can be set to other standard rates from 2400 to 115200 through HydroSoft or the BAUD command described below The Gamma 2 waits until it receives a carriage return and or line feed before responding to a command When it is not actively logging data 1t retransmits each character it receives Character echo is disabled during logging so that commands can be sent without affecting the output data stream Commands are case insensitive They are shown below in upper case for clarity Some commands accept arguments which are separated from the base command and from each other by commas or spaces Arguments may be individually omitted if commas are used as placeholders for them For example if a command accepts three arguments in the form COMMAND arg1 arg2 arg3 you may adjust o
14. ion This is automatically used by HydroSoft when it connects to an instrument 5 2 9 LOG period delay startOnPower Displays the current logging settings and changes them if valid values are provided Period is the number of seconds between samples which has a minimum value of 0 1 Delay is the number of seconds the first sample will be delayed after logging is initiated not implemented in firmware version 1 00 StartOnPower controls whether logging will start when power is first applied to the instrument Note that startOnPower may be overridden by the start stop switch depending on its setup See section 3 2 for switch details Changes you make to the LOG parameters will not be retained when power is removed from the instrument unless you use the STORELOG command to make them permanent 5 2 10 SENDCAL Sends the entire contents of the instrument s internal cal file if any through the serial port aia 5 2 11 SLEEP seconds Sends the instrument into its low power sleep mode Logging and any other activities are stopped during sleep If seconds is specified the sleep will end after that time interval has passed Otherwise it will sleep until woken by the switch or serial port activity 5 2 12 START Starts logging with the current log settings using the next sequential cast number 5 2 13 STOP Stops the current logging cast if any 5 2 14 STORELOG Stores the parameters of the LOG command in nonvolatile memory 5 2
15. ital counts 5 OS Es n 0 1 PER P P coe D ap P P P 5 1 k py gt gt Kon P P gt P n 0 where P and P are values of P T The fully calibrated attenuation coefficient is given by where m1 1 t T P L is the path length in meters T Tpw 0 is the transmission measured in pure water at temperature Ty and atmospheric pressure 6 5 Calibration File Format guaranteed and it is possible additional parameters could be added in future versions Therefore any software that reads the file should identify parameters by their labels not The calibration file whether stored in the instrument or on the computer running HydroSoft is a plain text file in the following format The sequence of parameters is not 22 their sequence Table 1 shows the plain text names used in the calibration file for the terms in the formulas above Any line in the calibration file may also include a comment after the parameter value marked with a double slash General DeviceType Gamma 2 Saved by HydroSoft 2 80 Serial C2100000 Label HOB Config 100 MaxDepth 6000 CalTime 1270080000 04 01 10 Depth kp1 10 215 kp2 0 1624 P0 1439 TP0 26 68 kD1 0 3619 kD2 0 Attenuation 1 Name c470 Lambda 470 DeltaLambda 10 L 1 005 S0 3 RO 0 kTO 0 9926 kT1 0 0031851 kT2 0 0002447 kT3 4 8421e 6 kT4 0 kT5 0 P1 50 P2 103 kTauPX 0 1188 kTauP0 66 kTauP1 1 0771e 5
16. lects and averages data internally at 1000 Hz and the values transmitted and logged are averages of these rapid samples In general a packet is an average of all the values collected since the previous packet and until the moment the current packet is sent In other words if it is logging data once per second the value reported at time X is actually the average of the value over the times from A 1 to X seconds The time value reported in the packet is X the end of the sampling interval For sample periods up to 8 seconds all the rapid samples are given equal weight in the average For longer periods older samples are given gradually decreasing weight At the beginning of a data cast started with the switch or START command older samples are flushed from the average so that the first packet reported will include the same number of averaged samples as subsequent packets 3 3 Power up Sleep Mode and Switch Control Gamma 2 provides various options to control its power mode and its response to the switch on its end cap Figure 4 For most applications there is no need to change from the default settings 3 3 1 Default Setup The default configuration provides simple control of logging with the switch or with real time control by HydroSoft Setting the switch to start wakes the instrument if it is asleep and starts logging Setting the switch to stop ends the current logging cast and puts the instrument into low power sleep
17. lways retained 3 3 5 Using Power to Control Logging Note that while it is possible to use Sw startsCast setting Stan cast Figure 5 Program flow when power is first applied Wait for the Gamma 2 in a dumb mode where commands you initiate logging simply by applying power to it you should not end casts by simply removing power Cutting power while a cast is in progress will definitely result in the loss of up to 30 seconds of buffered data from the cast and in addition creates the risk of damaging the entire flash file directory and losing all logged data completely 3 4 Deployment 3 4 1 Mounting In order for the Gamma 2 to be safely lowered on a cable it must be secured in a frame or other structure that provides a suitable attachment point Figure 6 shows the recommended frame supplied by HOBI Labs The figure also shows a battery pack attached to the frame which is required if the lowering cable does not have conductors for supplying power The frame shown here has several features that make it very secure if it is assembled and used properly It consists of two pairs of clamps that go around the main housing of the Gamma 2 The lower pair has a smaller inside diameter that matches the diameter of the Gamma 2 s waist and ensures that it cannot possibly slide off the instrument The upper pair of clamps is rigidly connected to the lower pair with stainless steel rods so the clamp pairs pr
18. nly arg3 by entering COMMAND arg3 5 2 Common Commands 5 2 1 BAUD newrate Reports the current baud rate of the instrument If a valid newRate is specified 2400 4800 9600 19200 38400 57600 or 115200 the rate will immediately change Note that because of the time required to transmit data packets lower baud rates may limit the maximum sampling rate 5 2 2 CLEARLOG Deletes all cast files from flash memory and resets the cast number to 1 Because this will result in permanent loss of data the firmware asks for confirmation before proceeding Deleting large and numerous files can take up to several minutes 16 5 2 3 D Sends a packet with the most recently collected data 5 2 4 DATAFORMAT formatNumber Sets the format of packets that will be sent during logging cast downloads and in response to the D command As of firmware 1 00 formatNumber can either be 0 to indicate a brief packet or 1 to indicate a full packet see section 6 1 for details 5 2 5 DELCAST castNumber Deletes the given cast does not prompt for confirmation Does not affect the current cast counter 5 2 6 DIR Displays a directory of the casts in flash memory including their start times durations and number of samples 5 2 7 DOWNLOAD castNumber Sends the data from the given castNumber if any from the Gamma 2 in the current data format 5 2 8 ID Displays identifying information about the instrument and its configurat
19. ort multiple path length options up to a full meter the standard path length is 30 cm The optical path is completely open to natural water flow so no pumping is required and the instrument contains no moving parts The electronics include an intelligent controller with internal logging and large flash memory capacity 1 1 Opto electronic Design Figure 1 shows a schematic view of the beam optics The two wavelengths are generated by separate LEDs Each LED s current is controlled through software and modulated at a frequency and phase that allows it to be distinguished from the other The LEDs beams pass through diffusers not shown and then a beam splitter that directs a portion of each to the output beam and a portion to a reference photodiode The reference photodiode and its associated preamplifier electronics are identical to those used to receive the signal after it passes through the water except that the signal preamplifier has much higher gain For both the reference and signal measurements the signals from the two LEDs are separated from each other through digital synchronous detection The source and receiver lenses have 100 mm focal lengths and 1 mm pinholes at their focal planes make the beam divergence and receiver field of view less than 0 5 full width in water The beam exits the source window with a 5 mm diameter and over a 1 m path expands to 14 mm Signal Detector Pressure Windows i Le a E Retro i
20. ose the Date Time dialog box Collecting Data Select Sampling Options from the Gamma 2 menu For testing purposes we recommend the following settings Sample Rate 2 per second Start Delay 0 seconds Burst mode unchecked Select Plot Vs Time from the Graph menu Click start or select Start from the Gamma 2 menu This will cause data to be logged in the flash memory as well as sent to HydroSoft If no data are visible after a short time click El and the plot will zoom as needed to show all data To adjust the way data are displayed double click on the graph or select Properties from the Graph menu e Click D or select Stop from the Gamma 2 menu e Close the open data file by selecting Close from the File menu or clicking on the HI button If desired save the file when prompted 2 3 Downloading Logged Data e Select Get Data From Instrument from the Gamma 2 menu e After several seconds a directory of casts in memory will appear The last cast listed should be the one you just recorded If that cast is not already highlighted click on it to highlight it or click the Select All button e Click the Browse button to select a directory in which to save downloaded data files In the resulting dialog box select a directory and click the Select button e If it is not already checked check the Create calibrated data dat files option e Click the Download button to begin transferring data casts 2 4 Disconne
21. ovide mutual support A forged stainless steel eye is threaded into the top of each rod and it is to these four eyes that user can secure a 11 lowering harness If using rope to attach to these eyes do not use a single loop of rope threaded through all four because that would be vulnerable to a single point failure by the rope Use one loop for each pair of eyes or some other redundant arrangement Figure 6 also shows a clamp pair on the lower end of the instrument This simply provides convenient protection for the instrument housing during handling especially when it is laid on its side on deck It also allows it to stand on end as shown in the figure but never leave the Gamma 2 standing unsecured and unattended 3 4 2 Real time cable connection If your deployment cable has the necessary electrical conductors you can power the Gamma 2 and communicate with it in real time including controlling it with HydroSoft However the limitations of typical electrical cables make this impractical for applications that exploit the Gamma 2 s extended depth capability To provide adequate power to the instrument the cable s round trip resistance must be 100 ohms or less and real time communication may require even lower resistance This limits practical cables to at most a few hundred meters length and possibly much less If you intend Figure 6 Gamma 2 Abyss with deployment frame and battery always test the cable and ins
22. s probably sufficient cleaning between casts For more thorough cleaning and work in dirtier waters you can use solvents including e ethanol e weak detergent solutions and e lens cleaners such as part number NT54828 at http edmundoptics com For the most thorough possible cleaning use each of these in the order listed and follow with a pure water rinse In relatively clear water it is adequate to do such a thorough cleaning only once per day In water rich with growth sediment or oily substances more frequent use of solvents may be necessary always followed with clean water NOTE do not use acetone or other harsh solvents which can attack the plastic retaining rings and o rings 13 4 BATTERY PACK The Abyss battery pack is an ideal companion for the Gamma 2 Abyss in deep profiling applications It matches the Gamma 2 Abyss s 6000 meter depth rating and has enough rechargeable capacity to power the Gamma 2 for at least 24 hours of continuous data collection 4 1 Description The battery pack case is 8 7 cm 3 45 in diameter 24 3 cm 9 55 long and is made of hard anodized 7075 aluminum The anodizing and a zinc anode on the connector end cap protect against corrosion in water as long as there is no electrical contact between the case and other metals Plastic mounting brackets such as those supplied by HOBI Labs see Figure 6 ensure proper insulation The pack includes a pressure relief valve to
23. the signals measured by the reference detector before the beam enters the water e Pressure is the raw digital reading of the pressure transducer e Templ temp2 and temp3 are temperatures measured at three different places within the instrument not water temperature The reported values are 100 times the actual temperature in C e Vin is the supply voltage input Its value is 100 times the actual voltage e Bend Smin Smax Rmin and Rmax are state of health indicators showing the signal levels at different parts of the circuitry e N is the number of samples averaged to produce the packet Normally this will be 1000 times the sample period in seconds If you use the DATAFORMAT command to set the data format to 0 a briefer version of the above is produced which is identical except that it ends after temp3 The brief packets are sufficient for producing calibrated data so you can speed downloads of large data files by selecting this format The default DATAFORMAT setting is 1 producing the full packet shown above 6 2 RAW File Format HydroSoft s raw files start with a header similar to the following but the exact contents or sequence of the header are not guaranteed to remain the same in all versions of HydroSoft 19 Header HydroSoftVersion 2 80 CreationDate 04 10 10 14 49 43 FileType raw DeviceType Gamma 2 DataSource G2100100 CalSource Gamma 2 Serial G2100100 Config 100 EndHeader Following the
24. trument beforehand in pack also see section 4 the deployment configuration Warning do not leave the instrument standing this way without securing it to use a real time cable connection for deployment 3 4 3 Battery powered deployment The Gamma 2 works seamlessly with a battery pack to provide data logging without any electrical connection to the surface For battery power profiling you can leave the battery connected continuously and start and stop logging with the end cap switch Each switch activation will create a new numbered cast in flash memory 12 3 5 Cleaning Cleanliness of the windows is critical to the Gamma 2 s measurements Because it is sensitive to fractions of a percent change in light intensity even a tiny speck of contamination can make a significant difference in the readings Fortunately cleaning is not difficult and the instrument s sapphire windows are difficult to damage The degree of cleaning required depends on the environment in which the instrument is operating and the deployment routine The most basic but one of the best cleaning steps is to rinse the windows with generous quantities of distilled or deionized water This should always be the last step in your cleaning process and is highly advisable each time the instrument is withdrawn from the water so as to prevent substances from drying onto the windows If the water you are measuring is among the clearest natural waters this alone i
25. witch only acts when moved from one position to the other and its position can be overridden by software commands For example if the switch is in the stop position you can still start a data cast from HydroSoft or by sending the START command If you move the switch to the start position while that cast is still in progress it will have no effect but moving it back to the stop position will stop the cast if the StopsCasts parameter of the SW command has its default setting The one case in which the switch can affect the instrument s behavior without being moved from one position to the other is when power is first applied If the switch is in the start position applying power will always wake the instrument and it will start a cast if the switch s StartsCasts parameter is set to 1 3 3 4 Power up Behavior Figure 5 shows how the Gamma 2 reacts to the application of external power depending on its various command options When all options are set to their defaults the 10 instrument will either boot into the wait for commands state or if was put to sleep before power was last removed it will remain asleep If it is not waking from sleep the Gamma 2 will reboot each time power is applied The reboot is completely safe and normal but resets volatile parameters such as logging settings that have not been stored with the STORELOG command see section 5 2 14 The real time clock Switch Postion setting is a
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