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ac-s User’s Guide (ac-s)

Revision F

9 Feb. 2006

Spectral Absorption and

Attenuation Meter

ac-s

User’s Guide

WET Labs, Inc.
P.O. Box 518
Philomath, OR 97370
541 929-5650
www.wetlabs.com

Summary of Contents for ac-s

Page 1: ...ac s User s Guide ac s Revision F 9 Feb 2006 Spectral Absorption and Attenuation Meter ac s User s Guide WET Labs Inc P O Box 518 Philomath OR 97370 541 929 5650 www wetlabs com...

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Page 3: ...cannot accept instruments for servicing or repair that are treated with anti fouling compound s This includes but is not limited to tri butyl tin TBT marine anti fouling paint ablative coatings etc P...

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Page 5: ...s and labor and pay for return via 3rd day air shipping in honoring this warranty Shipping Requirements for Warranty and Out of warranty Instruments 1 Please retain the original shipping material We d...

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Page 7: ...and Data Output 11 3 4 Data Format 11 3 5 Post Processing 11 3 6 Temperature dependent Absorption Correction 13 3 7 Scattering Correction 14 4 Calibration and Characterization 15 4 1 Temperature Corr...

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Page 9: ...is different from the absorption tube Its flow chamber is plastic and the two sleeves on the tube are identical This tube installs on the c side of the instrument the side with the identical looking w...

Page 10: ...4 Figure 4 You should measure the power supply voltage across these two pins 3 Turn the power supply off 4 Connect the pigtail to the instrument Push the connector straight on to avoid damaging the pi...

Page 11: ...deploy If the values are outside this range the first step is to re clean the instrument and then reapply the CAL file offsets 1 4 Cleaning 1 Remove flow tubes and all O rings Remove the sleeves from...

Page 12: ...of data and the values should not vary more than 0 005 m 1 over the 10 minute time period 8 Collect data Record a one to two minute file and save data Repeat steps 4 6 until you can collect three data...

Page 13: ...ons Data from the ac s is transmitted via both RS 232 and RS 485 depending on which sockets are connected to the instrument s bulkhead connector Regardless of the mode of transmission you use you must...

Page 14: ...o the ac s Applying a small amount of silicone grease or equivalent to the base of the instrument bulkhead makes the plug insertion easier and provides greater assurance of a good seal Use a connector...

Page 15: ...lowing basic procedures 1 Do not make direct contact between the ac s pressure housing and a metal frame or hose clamp The ac s is available in one of two pressure housing materials Aluminum is used f...

Page 16: ...o shock The data will be adversely influenced by bubbles dirt or grease in the flow path or misalignment of the flow tubes Make sure that the flow tubes pump tubing and screens are free of dirt and gr...

Page 17: ...n deck and lash it down Give the cage and instrument a fresh water wash down after every cast If this is not practical wash the instrument at the end of each data collection day Holding a hose at low...

Page 18: ...WARNING Do not use acetone on the windows It will damage the window holders 2 Wash the windows The windows should be cleaned with dilute soapy water followed by ethyl alcohol and should receive a fin...

Page 19: ...3 Digital Processing and Data Output The CPU takes multiple samples of both signal and reference channels accumulates them through the sampling period and then averages the values at the end of the s...

Page 20: ...bration and Characterization We therefore can solve for c or a by c 1 x ln Csig Cref ln N 4 or c 1 x ln Csig Cref 1 x ln N 5 or c ln N x ln Csig Cref x 6 Since the ac s pathlength is a fixed constant...

Page 21: ...fect must be considered to correct the absorption and attenuation at wavelengths above 700 nm Experimental results show that aT the water specific absorption correction due to temperature at 715 nm is...

Page 22: ...ust be corrected to obtain accurate absorption values There are several alternatives in performing the scattered light correction The simplest involves subtracting the temperature corrected a715 measu...

Page 23: ...alf to one degree Celsius through the operational temperature range of the instrument From these values we generate a table of temperature compensation offsets Tn This table is contained in each instr...

Page 24: ...g lasers used in lectures work very well for this task If you see more than one or two large scatterers in the beam path your water is unsuitable for a clean water calibration WET Labs and researchers...

Page 25: ...it Effective air calibration requires 1 The instrument s optical path is clean and dry 2 The instrument s optical path is completely shielded from ambient light To perform air tracking we recommend th...

Page 26: ...tion of 0 002 m 1 or less above 450 nm If you have a substantial slope to the data over the acquisition period your meter may have some residual moisture in the flow tubes or on the windows If the opt...

Page 27: ...10 cm available Beam cross section 8 mm dia nominal Linearity 99 R2 Output wavelengths 80 90 Resolution 4 nm Precision 450 750nm 0 001 m 1 typ 0 003 max 4 Hz 0 0005 m 1 typ 0 0015 max 1 Hz Precision...

Page 28: ...rrangements Sea Test Cable Connector Pin or Socket Function 1 Common 2 RS 232 Receive 3 RS 485 4 Voltage in 10 to 35 VDC 5 RS 232 Send to Host 6 RS 485 Voltage supplied to the instrument is internally...

Page 29: ...this socket Pin and socket assignments for the pump power connector are shown below Figure 5 Pump Cable Connector Pin and Socket Assignments Pump Power Cable Connector Pin or Socket Function 1 Common...

Page 30: ...pect both tubes and make sure they are free of stains and dust The reflective flow tube for the absorption measurement operates using the principle of internal reflection To maintain its reflective pr...

Page 31: ...rom both filter sections Each filter covers approximately a 72 degree section of the beam path across the filter wheel The filter wheel rotates at a tightly controlled 8 0 rps such that the shorter wa...

Page 32: ...ore subject to both scattering and absorptive losses by the water Once through the water path the light passes through another pressure window and then is re focused through a lens upon a receiver det...

Page 33: ...ion encoder two incandescent lamps and four photodiode detectors 6 4 Signal Processing The purpose of the ac s signal processing circuitry is to take a raw optical signal and make it into a physically...

Page 34: ...rsects one filter section for about 1 8 revolution before the a beam intersects the other filter This staggering of the filters relative to the beams is the reason for the phase differences between th...

Page 35: ...required to send the data and requirements on the CPU during sampling the next data sample is not captured until a full even number of revolutions have passed following completion of the data averagin...

Page 36: ...17 c9 12 d8 14 0a0 32 10 ce 1a 25 14 d2 16 17 12 61 1c b5 16 e8 18 0b0 20 14 08 1f 85 19 2b 1a 5b 15 e7 22 8e 1b ad 1c 0c0 be 17 d8 25 c7 1e 5d 1f 3d 19 ef 29 33 21 3b 21 0d0 e4 1c 17 2c d5 24 48 24...

Page 37: ...4 ff00ff00 Packet registration 013 2 02D0 Record length of full packet not including chksum 720 015 1 05 Packet Type 03 and above designates an ac s meter 016 1 01 reserved 017 1 53 meter type 53 ind...

Page 38: ...t two bytes are the A D counts from the pressure sensor circuitry If no pressure sensor is installed these two bytes may be ignored When a pressure sensor is installed the depth in meters can be calcu...

Page 39: ...senting the number of output wavelengths Next is the data for the scan The values are the averaged signal counts dark count subtracted for each detector at each output bin The counts are 16 bit unsign...

Page 40: ...32 ac s User s Guide ac s Revision F 9 Feb 2006 Figure 10 ac s system diagram...

Page 41: ...e oil from escaping from the reservoir into the water However you may occasionally wish to ensure that oil remains in the reservoir on top of the transducer WARNING Never touch or push on the transduc...

Page 42: ...er this common mode noise will be most apparent To eliminate this noise issue either the laptop the power source or the meter itself needs to be connected to an earth ground i e the ground receptacle...

Page 43: ...Rhoades B 6 29 04 Update specifications DCR 401 D Stahlke I Walsh C 12 2 04 Update Appendices to reflect optional pressure sensor and common mode noise DCR 439 B Rhoades D 4 11 05 Add ac 9 Protocol D...

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