On Tue, 18 Jul 2006 00:59:11 GMT, John - KD5YI Gave us:
It is still going to exhibit problems. A production scale run of such an assembly will have quite a high failure rate, and one will find that a good cleaning and baking cycle will begin to bring proper circuit function back into focus.
Up to 350G in an 0603
Best regards, Spehro Pefhany
-- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
Or 10M or 22M -- DigiKey stocks standard Pansonic 5% chip resistors to those values in 0603, e.g. P22MGCT-ND.
Best, James Arthur
On Mon, 17 Jul 2006 22:36:10 -0400, Spehro Pefhany Gave us:
The catch? NOT for HV. At the voltages given, one could practically count the electrons that would pass by hand... ;-]
Very little stimulus.
Absolutely NO use whatsoever for HV applications. I was regularly using 10kV, 15kV, and 20kV feedback resistors between 500MOhm and
100GigOhm. I could fashion any HV load array. I made HV probes, and I made any loads we needed for testing product at bench or even production line. Even huge load banks with 25 HV load point taps on it, all safely scoped out. HV resistors are great for making a "ripple checker" for HVDC ripple (even low voltage, it's accurate). It gets placed on the HV line, and the scope probe goes on the probe tap. There is a neon bulb to clamp any voltage over 90 Volts, and those can be seriesed to increase that. Whatever you would max allow into your scope.We had a PMT PS that could only have like 5 picoamps leakage at the output. At 1.5kV this is no easy feat. The "tube" style connector even leaked, and we had to research to find one that didn't. We also used high value SMD resistors for the PMT splitter array. That PCB assembly had to be REAL clean for it to work. We even had a vapor phase system at one time. We used Ensolve (great product). No banned solvents. RTV potted. Finished PMT product can detect single photon event, such as a ground based missile launch several tens of miles away from the wing of a plane. Gotta keep the noise out.
"Phat Bytestard"
** No one is talking about HV applications except * YOU* Fat Head.The OP clearly indicated the 1G resistor was for a " ... low noise application".
Now, get off that HV hobby horse of yours before it turns around and bites you on your fat ass.
........ Phil
On Tue, 18 Jul 2006 14:45:48 +1000, "Phil Allison" Gave us:
Actually, his first post mentioned a class of resistors that are HV, and he never did say what the application is.
Low noise does not have to mean low voltage, Phillisteeeen.
Oooohhh, big man with small appendage maketh much noise. I guess you would even fail as a resistor. That would be all you would be good for. Put you in an arena, place a tazer collar on your ass, and watch you dance, taking bets on which jolt will finally get ya.
On 17 Jul 2006 20:32:48 -0700, snipped-for-privacy@yahoo.com Gave us:
I am talking about when one examines a standard product line chart. The resistors you mention are specialty items. It is even hard to find such items in a standard offering in axial leaded versions.
Sure, they are, and have been available for some time, but they are not typically in the standard offering chart for a given line by the maker. Sure, there are some makers where that is actually their specialty. I am familiar with them. One is one you all mentioned Ohmcraft. Caddock is another. Not for the average consumer hobbyist, however.
Anyway, it will come down to what the application is for it, and what level of noise you can handle, and where your noise floor will be downstream.
For an HV app, these will likely not cut it. For an LV app. where can you possibly need such a small division? Also, just farting in the room can change it at those voltages. LOTS of false readings.
On 17 Jul 2006 13:17:32 -0700, snipped-for-privacy@yahoo.com wrote in Msg.
What's that? A bar of glass with endcaps?
robert
Loathe as I am to admit that the Phat Bytestard can get anything right, he seems to be on the ball here.
At Cambridge Instruments, where we did use 1G resistors from time to time, the tendency was to mount them on Teflon insulated stand-offs - Farnell call them "Press-Fit PTFE Components" which is not a helpful choice of name. Farnell order code 143-376 uses up least board space - it needs a 2mm diameter hole.
This uses up a lot of board space - but no more than you need for high-voltage clearances - and was much more difficult for production to screw up than thorough cleaning followed by encapsulation.
-- Bill Sloman, Nijmegen
On Tue, 18 Jul 2006 15:00:38 +1000, "Phil Allison" IS:
Is there any thread that you do not troll folks in?
Aside from your numerical age, do you actually consider yourself to be an adult?
On Tue, 18 Jul 2006 15:00:38 +1000, "Phil Allison" Gave us:
Resistor noise is related to the composition of the resistance medium used to make the resistor, asswipe. So you can apply your stupid, adolescent remark to yourself.
Yes. And a squiggly puff of dragon's breath.
Cheers, James Arthur
"Phat Bytestard" = Fat Head Fuckwit
** I still see you know FUCK ALL about resistor noise too.How unsurprising.
** Get back to your Phat Chik p*rn sites - you asinine freak......... Phil
Guys, thanks a lot. I got couple of samples from ohmcraft. Think will do the job. People have been telling about using tweezers and gloves to handle these resistors which ofcourse i am going to follow. Are there any more comments - my PCB is from FR4 and will sit in vacuum at 4 kelvin. So i'm not concerned about contamination or humidity once the PCB goes in the system.
-arch
Phil Allis> "Phat Bytestard"
"Arch"
** Huh ???" 4 kelvin " ????
That is awfully cold.
Won't the resististor freeze its poor little end caps off ........
........ Phil
On 24 Jul 2006 11:39:41 -0700, "Arch" Gave us:
You should always worry. Skin oils and even coffee breath can set up pathways for electrons that you cannot see, lowering the value of the resistor dramatically, and it won't show up on a low voltage test either. As potentials rise, however, leakage will occur on dirty parts much more readily than clean part, and the fact that it is in a vacuum wont matter.
PC boards as well as some part package materials are hygroscopic.
The last step you should take with that assembly is a hot IPA bath (or vapor phase even), and a good bake at 60C for a half hour or so in a dry oven, then even a good vacuum draw on the assemblies themselves for about 5 minutes will draw even more water out of the PCBs.
THEN without touching any HV areas (if that is the case), you can place your assembly in your cold, low pressure setup. Unless you plan on encapsulating or conformally coating it. Remember, even those skin oils can outgas as you pull the vacuum down. Even if they are trapped under a coating or encapsulant.
A clean, VOC assembly is always the rule anyway for longevity and reliability.
Especially if the application uses elevated potentials.
On Tue, 25 Jul 2006 10:05:36 +1000, "Phil Allison" Gave us:
If it has any... no.
Actually the thermal expansion coefficient of the end cap material is likely greater than that of the silica tube, so if anything, the caps would get tighter.
"Phat Bytestard"
** Then fracture and fail.Makers specify the minimum operating temp as -55 C for good reasons.
........ Phil
Most ordinary parts keep working down to liquid helium temps, except obvious things like electrolytic caps. PN junctions quit working below, roughly, 20K ("carrier freeze-out") although fets keep working.
John
On Tue, 25 Jul 2006 13:23:49 +1000, "Phil Allison" Gave us:
Mostly moisture concerns. In air, a part below dew point will condensate water.
In chilled fluorinert, a circuit will run just fine, and far less noisy. In chilled LN, even better. Just can't raise it up out of the bath, it will condensate water immediately from the air.
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