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Posted: 12/13/2007 10:31:46 AM EDT
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I was wondering if someone could go through all the different stats on a tube data card and explain what they mean, just in general, you dont have to go crazy...and mabey also say if its better to have a lower or higher number, as some stats its better to have low such as halo i think... anyway here is a list of everything on my card: PART NUMBER: (this one needs no explaining) FTYPE: DOWNGRADE: START TYPE: GATE TYPE: POT TYPE: FOM: (next one is always blacked out, wondering why?) SIGNAL TO NOISE: RESOLUTION: HALO: ZFINAL WHITZE PR: EBI@800: FILM TYPE: CATHODE VOLTAGE: *NOT FOR USE IN AVIATION* (I have heard if they have ANY blems, no matter how small they can not be used for avaition, and I also heard the military gets ALL the avaition tubes) <--- I could be way off on this one... then there is a bar code... also the date it was made is printed up the right side... I have also heard that if you divide the FOM by the SIGNAL TO NOISE you get the true resolution of the tube...on most tubes (alfa select) it equals 64 just like the RESOLUTION listed, but on mine it equals 73, I was told this buy the company who sold me the tube, saying it was a kick ass tube with a "true res" on 73, is there any truth to this or is this BS? Last, if we get some good answers mabey Victor will tag this so people new to NV or thinking about buying will know exactly what all the stats mean. |
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A: The basic rundown of the most frequently used night vision acronyms... ABC (auto-brightness control) - A built-in feature which automatically reduces voltage to keep the image intensifier's brightness within optimal limits and protect the tube. AN/PVS - An assigned military designation for fielded night vision devices. "AN" meaning "Army-Navy"... and... "PVS" meaning "Passive Vision System". Examples: AN/PVS-7, AN/PVS-14, etc. "ANVIS" is typically designated for military aviation usage ("Aviator Night VISion", or, "Aviation Night Vision Imaging System"). Also used is "AN/AVS" (Army-Navy / Aviator Vision System). Examples: AN/AVS-6, ANVIS-9, etc. BSP (bright source protection) - Somewhat similar to auto-brightness control in protecting the photocathode from moments of extreme and / or direct bright light exposure (such as automobile headlights, flashlights, room lights, etc.). BSP, while not incorporated into every NVD unit, will cut the voltage to protect a tube from damage. EBI (equivalent background illumination) - The measured amount of lowest light at which an object can be detected. The lower the EBI value, the better. FOM (figure of merit) - An image intensification tube designation often used for legal export classifications. Figure of merit can be determined by using the following calculation: Lp/mm x SNR (signal to noise ratio) = FOM FPN (fixed-pattern noise) - A characteristic most often seen through 2nd and 3rd Gen. devices under bright light conditions. A notable "honeycomb" or "chicken wire" pattern of the unit's micro channel plate can be seen within the field of view. This is normal and of no cause for concern. Lp/mm (line pairs per millimeter) - A measurement used to determine a "resolution" rating of NVD tubes. A test pattern, which consists of a series of different sized patterns of three horizontal and three vertical lines is used. You must be able to clearly distinguish all the horizontal and vertical lines, including the spaces in-between, to qualify for a designated resolution pattern rating. Higher lp/mm numbers equate to higher resolution (sharpness in detail to the object being viewed). SIDE NOTE: Though many 1st Gen. units advertise a 40lp/mm resolution (which may seem higher than 2nd Gen. resolution ratings of 28-38lp/mm) this is only measured from the absolute center of view, as opposed to the overall view. If you have a tube data sheet and would like to determine your actual Lp/mm rating, you may use the following calculations: FOM (figure of merit) divided by SNR (signal to noise ratio) = Lp/mm MCP (micro channel plate) - First used in 2nd Generation NVD's, the MCP is a wafer-thin charged disc containing millions of holes which increases electron output as electrons pass through. This in turn allows the photocathode to produce a significant increase in gain, as well as nearly eliminating the geometric distortion inherent of earlier 1st Gen. units. NVD / NOD (night vision device / night observation device) - Two of the most commonly used acronyms for night vision units. "NVD" seems to be the most widely used term by civilians, while "NOD" is often used by those within the military. "NVG" (night vision goggles) is typically used for dual-eye / bi-ocular, hands free units such as the military's AN/PVS-7 goggles. PR / PS (photoresponse / photosensitivity) - The ability of the photocathode material to produce an electrical response when subjected to light waves (photons). The higher the value, the better the ability to produce a visible image under darker conditions. SNR (signal to noise ratio) - A measure of the light signal reaching the eye divided by the perceived noise as seen by the eye. A tube's SNR determines the low-light-resolution of the image tube; therefore, the higher the SNR, the better the ability of the tube to resolve objects with good contrast under low-light conditions. Because SNR is directly related to the photocathode's sensitivity and also accounts for phosphor efficiency and MCP operating voltage, it is the best single indicator of an image intensifiers performance The black line through the data card you see covers up the word Pinnacle. Unless its Autogated its not a true Pinnacle tube (technically so to speak because the real difference lies in the autogated power supply. A thin film tube is not a Pinnacle without it)Most tubes in commercial use are not autogated but still great tubes !Some things not covered are downgrade codes and this is some of them(as a side note all non Milspec tubes were downgraded for one reason or another.In NO way does it mean its a bad tube.It could of just had a small spot in the wrong place.Many Commercial tubes well exceed Milspec tubes in performance.The most common cause for rejection would be blemishes (spots) of some sort. Milspec just means the tube met the minumum performance standards set by the military for that type of tube. The S/N standard may be only 21 for a Milspec tube and many commercial tubes have a S/N in the very high 20,s and some even in the 30,s GZ = blown aluminum (spot)Halo: Is the halo effect you get around a streetlight or some other bright light source. The lower the number the better.Ftype : Filmed or Thinfilmed (thinfilm tubes generally perform better and are more advanced.This is not always the case but most of the time.) Here is a good link to explain filmed,thinfilm or no film technology. http://www.nightvision.com/military/cs_gen3pinnacle.html Pot type: Potting means instalation of the power supply, therefore all tubes are "potted". However, testing of the tubes (which result in the Data Card) can be performed with or without the power supply which is noted on the Data Card as POTTED/UNPOTTED. Tube lifespan depends on many factors, both internal and external in source. Generally, if you keep your unit properly protected from continuously extreme bright light exposure, these are the average lifespan of tubes by generations... 1st Generation = 1,500 hours 2nd Generation = 2,500 to 3,000 hours 2nd Generation SHP = 5,000+ hours 3rd Generation = 10,000+ hours Some of this information is copied and some my own.It saved on alot of typing by copying some things. Putting it all in one place should help people. Thank you to the people I copied info from. (I am sure they know who they are).Victor please feel free to edit if anything is incorrect or can be made more clear. Hope this helps! |
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WOW...NICE answer, I hope this gets pinned at the top... Some of the info I knew a little about, most i did not, its nice to have it all in one place though...my problem is i will learn something, then a few months later not remember the answer... My down grade is: RZ...do you know what that stands for? also I have seen: ND..wonder what that means? |
| I am sorry I do not know what those downgrade codes are. I got mine from Stanley over at night vision forums who originally posted this some time back. I don't see him online much anymore but if I do I will ask for you. Seems downgrade codes are sort of a guarded secret By ITT. You can't find them anywhere unless someone that worked there leaked them out.Stan said there are many of them but these are the most common. |
So many people have asked this question with ITT. As most know when the tube is downgraded from a mil-spec to commercial, these codes are used. There are MANY codes as you can imagine and I remember having a conversation with an ITT engineer awhile back and he was even perplexed on all the codes since some were actually outdated.  I hope this helps a bit and I will ask again. Vic |
Vic, thx for the respnce...not a huge deal, was just curious... i also was reading today about blemishes in tubes... i have a few very small blems i noticed in my tube that im pretty sure were NOT their before, the are small, iregular shaped and have crisp edges, i read that it may just be dust or debris on the photocathod or phospher screen or something and can be cleaned off then re purged... vic, a little off subject but did you ever do further testing with the 557 and NV? pm me with your findings if you got any new info... |
sounds like a dusting and cleaning is in order |
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Here's a little bit to clarify ABC and BSP Automatic Brightness Control actually protects the user, not the goggles. It adjusts voltage across the MCP to control the number of electrons traveling to the phosphor screen and thereby maintaining a constant brightness. This protects the viewer when bright flashes or lights are introduced. So, the next time you watch Patriot Games and Jack Ryan defeats the Irish terrorists by switching the lights back on, painfully blinding them with their NVGs you can say...they needed ABC! Bright Source Protection protects the goggles by protecting the component that really limits the service life of the intensifier....that is the photocathode. When high input light levels cause excessive photocathode current to flow, BSP reduces the voltage between the photocathode and the MCP. ABC protects you. BSP protects the photocathode. Bill |
Nitpick mode on: PVS is by no means 'Passive Vision System'. From military equipment code chart: P - pack or portable V - Visual and visible light S - Detecting and/or range bearing, search Nitpick mode off.. |
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