(Cosine) Collector manual - Hobi Instrument Services
Contents
1. likely entry point for water is where the cable s outer jacket enters the fiber optic connector This is normally covered by a strain relief boot as shown below This boot may or may not form a seal by itself SMA termination with boot SMA termination with boot removed The lower picture shows the blue jacket entering the metal part of the connector At some point inside the connector the jacket ends at which point it must be sealed In high quality commercial cables the connector is typically filled with epoxy encapsulating the jacket and providing an adequate seal However since the seal is internal the only way to be sure is to consult the manufacturer If in doubt you can provide extra protection by sealing the ends of the boot or even encapsulating it entirely with a waterproof adhesive such as the silicone caulking that is used for sealing aquarium tanks2. Underwater Fiber Optic Plane Irradiance Collector User s Manual Revision E July 2015 Hobi Instrument Services www hobiservices com Revisions E July 2015 New formatting and illustrations notes about immersion correction D May 1 2008 Correct o ring label on drawing C June 16 2004 Change o ring from 5 102 to 3mm x 1mm B June 16 2004 Add explanation of air optimized version discussion of cable waterproofing A June 13 2003 First release Description The Hobi fiber optic plane irradiance collector attaches to an SMA terminated fiber optic cable to provide a cosine weighted angular response to light under water it is also available in a version optimized for use in air but with the same waterproof construction When properly assembled the 4 Mounting holes for collector protects the sensitive end of the 4 socket cap screws 0 687 cent fiber optic from water Note that the fiber os 93 CENSIS optic cable itself supplied by the user must OG OQO also be constructed so as to prevent water from entering its own outer jacket See 1 4 36 Thread for SMA below for an explanation of this For the most robust water seals r Gland tor Parise such as those used in the underwater 2 014 O ring cables built into HOBI Labs instruments optional the collector includes mounting holes and an o ring gland for a face seal These can Gland for be used to incorporate it into a larger 3 mm x m
3. m o ring structure to seal and reinforce the entire o ring fits around fiber optic cable However those features SMA ferrule are unnecessary for many stand alone applications of the collector Supplied Parts e Collector e 2 014 o ring and spare needed only if mounting to a special fixture e 3mm x 1mm o ring and spares Using the Collector To provide a water seal place a 3mm internal diameter 1mm wide o ring around the end of the cable s SMA ferrule as shown in the photograph below before screwing it into place For best results tighten the connection by holding the end of the cable stationary rotating the collector This help to work the o ring into its groove without pinching it The connector should be hand tightened rather than using a wrench to avoid stripping the plastic threads Note that when you remove the SMA the o ring will generally remain on the ferrule and it is easy to overlook the fact that it is there Inserting SMA connector with o ring in place If the collector is to be mounted onto a sealing surface first place a lubricated Parker size 2 012 O ring in the larger groove around the SMA thread pass the end of the fiber optic patch cord through the sealing surface and then attach the cord to the collector Use 4 screws not supplied to attach the collector to the sealing surface Precautions and Maintenance e Keep the inside of the collector clean and dry e Cover the SMA fitting with tape or a
4. vinyl cap whenever the fiber optic cable is detached e Do not use a wrench to tighten the connector so much that it could damage the plastic threads e Do not use acetone to clean any part of the collector e Upon removing the collector from salt water before removing fiber optic cables rinse thoroughly with fresh water Effect of Immersion on Calibration When the light collector is immersed the change in index of refraction from air to water decreases its transmission efficiency If you have calibrated your system in air to indicate spectral irradiance the immersion effect will cause the reported irradiance to be too low You must multiply the indicated irradiance by a correction factor which depends on wavelength As shown in the following plot the correction factor varies from 1 54 at 300 nm to 1 33 at 880 nm 1 60 S S 1 55 Le E 2 1 50 S 2 5 1 45 O 5 1 40 w e 2 1 35 E 1 30 400 500 600 700 800 Wavelength nm Fiber Optic Cable Construction and Waterproofing Most off the shelf cables are constructed with a waterproof outer jacket but this alone does not guarantee the assembly is watertight The SMA connector on the end of the cable must also be properly sealed at the time of manufacture Most high quality cables are sealed in this way Further water entry into a cable will not necessarily cause problems Nevertheless it is best avoided and users should be aware of the following considerations The most
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