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Hello all.

I would like to find out about tolerances on a few things and get a good scale for some testing myself, as well as for more general purposes.

I recently created a simple way to control the plungers of syringes with incredible accuracy, probably far more than necessary. If there were no tolerances in the syringe, it ought to be about .5 microliters using a 1ml disposable syringe I had for medication purposes. I use these same syringes for pheromonal purposes since I can easily obtain them. I have yet to give my design a good and proper testing though because it seems that syringe tolerances are well above that.

I could probably decrease the tolerance in my plunger-pusher's design more, but first I want to know where the tolerances are for syringes, which syringes have the smallest tolerances, and how to further compensate for the ones already there.

First things first: the barrel size (obvious first way of increasing accuracy)

Any way in which I could reduce the proportion of area of a cross section of the barrel to length of it would obviously be the first and easiest way to increase the accuracy.

Well, I googled a bit, and found that among the normal syringes, the smallest I saw was a .3ml syringe, which is normally used as an insulin syringe for diabetic dogs. The barrel however is slightly shorter. And unfortunately, it would seem that no matter where I looked I could not find specs on the length or width of the actual barrel, only the needles. The needles however led me to think more about how a larger gauge (smaller width, so long as it could still properly suck up the material) and smaller length needle would be better because of something I had thought a bit of, but didn't (till recently) know the name. That name is...

Dead space (or waste space):

Waste space is the amount of space in the needle itself and in the gaps of the fitting between the needle and the barrel in which extra material is left behind.

After a bit of googling (haven't searched too hard yet though), the smallest amount of waste space I saw on a syringe (specifically with a 0.3 ml barrel) was .026 ml, or 26 microliters, which already should be well above the tolerances I can create with the plunger, even if I'm wrong about a few things. So I figured I might have already taken things over the top a bit. Which got me wondering for practical purposes at least...

What's the maximum concentration of a molecule anyone could practically dillute into a carrier? I believe I read somewhere about 5 mg/ml, but it could have been different, I don't remember too well. I figure in theory I'd like to be able to use the highest cocentration possible to make mixes, but still with <0.5 micrograms error in 99% of samples coming out in the final spray. But then that got me wondering...

How accurate is a sprayer? And which ones are the best to use? To be honest, I don't care at all if the bias on the data is off compared to what the manufacturers say, only the accuracy. Extreme bias can be compensated for, inaccuracy on the other hand...

So in conclusion I figured I have to test (in order of greatest importance in my mind)

1) Sprayer Accuracy
2) Syringe Accuracy and some data of my own about dead space etc.
3) My little machine

I would love to test my little plunger pushing guy to fing out if I'm right and where I'll still need to tighten up tolerances, but until I know how much tolerance there is in the other things that happens between the concentrate bottle and it diffusing from my skin, there's no point. I may be incredibly off or it may be even more accurate than I said, but there's no point discussing it or posting about it till we know the other stuff. So first...

I need a good scale. A really good scale. I'd like one that could measure micrograms if possible. After all, that's the measurement we love to use so much...

I could get just a milligram scale for some of the testing, but it would be a bit short. And if I want to find out not just the average of the data, but the spread (which is far more important imo), then I'll need a really accurate scale that at least shows tenths of mg. Idk if such a thing is at all affordable right now for me, but I'd like to look into the options. Right now I'd like to keep it under $50, but I figure I'll have to go much higher... but I will if I have to. Anything for the name of science!

Also, I'd like to know what togo's you guys would like me to test, as well as spray bottles in general. If I have an accurate enough scale I could also get us data on those first few weird partial sprays for an even more in-depth comparative analysis. I already am working on a small home-made robotic setup for mass testing the results so that all I have to do is press a button and record the results.

I currently have:
"¢1 ml, 28 guage, 1/2" needle length BD standard syringes
"¢Androtics togos and full sized sprayers (are these the same as the ones from TP? look the same...)

I currenty need:
"¢Alpha-Dream togos (any way of getting them just empty?)
"¢Any other popular or good sprayers you guys want me to test:
â—¦Love Potion, Liquid Alchemy

"¢Different syringe sizes, needle fittings, and needle lengths

The questions I would like answered most are:
"¢What goes on with the waste space? Do individual needles have much lower tolerances of what is left behind than populations of needles, just more bias?
"¢Where can I find information about syringe barrel lengths?
"¢In general more syringe specs and info...
"¢Where can I get a great scale?

I have a decent bit of robotics stuff lying around from when I used to compete, and have had the urge to start a project for a while. Therefore I'm hoping to use it to significantly speed up my ability to analyze data on certain phero-related stuff and return the results to you guys, as well as more projects in the future. Besides pheromones, that's one of my favorite things to mess around with.

Thanks all!

Edit: Grammar, mycode, and suggestions of togos to test
One more note: I figure to some extent, the dead space can be compensated in some way, even if the natural accuracy is low.

For example, in a gear chain, one can normally expect tolerances to build most of all in 2 places:
  • the space between gear teeth where gears are not perfectly meshed
  • anywhere where a structural element holding the gear chain together can become a spring and store energy. This is only prevalent when the force required is not enough to move the end of the gear chain with ease, or when the elements are not built or strengthened properly for their function.

The gear teeth can be a large problem when using pre-made parts which are meant to mesh easily without much effort, particularly in long gear chains. However...

If you are able to use a small movement in one direction before beginning actual movement, you can "take up the slack" in the gears, as all teeth will be contacting on the side they will be throughout the entire moevement in that direction.

In this case, the plunger can be moved slightly upwards before lowering the needle into the liquid. This way, the slack is taken up between teeth to a level usually below visibility to the naked eye, and a reference point from which all liquid is then measured is created. There is no need for anything but a rotation sensor to take up this slack properly.

I wonder if a similarly simple and robust method of compensating for the dead space in the needle is possible. If the dead space is of consistent tolerance within one needle (just not within a sample of multiple needles), then it ought to be fairly easy to compensate for it, because when using the same needle multiple times, most of the innaccuracy observed within the sample of multiple needles would be translated into bias for a single needle, and bias can be compensated for.


Also, does anyone know of a good way of cutting the needles shorter? That ought to significantly reduce waste space.

I was thinking of using something inside it to keep it from collapsing, and wire cutters or something like that.
Okay you are pretty damn smart. I have often wondered about those partial sprays and how much was actually coming out. You should ask Chris about getting some of his to gos. I would love to see LP's sprayers tested. I have a lot of their one ounce sprays. Also Liquid alchemy's.
Jeez, 26 microlitres margin of error only in the needle?

The more i read, the more i convince myself i need a pipette.

(03-12-2012 9:12 AM)halo0073 Wrote: [ -> ]Okay you are pretty damn smart. I have often wondered about those partial sprays and how much was actually coming out. You should ask Chris about getting some of his to gos. I would love to see Love Potion's sprayers tested. I have a lot of their one ounce sprays. Also Liquid alchemy's.

Well thank you! Big Grin

I'm most excited to get some from chris. His seem to have the smallest sprays by description, and he's the only one I've seen so far who lists the approximate average volume per spray (55 microliters). That in addition to the fact that not only does he list margin of error for molecules, but also what are the constituents of said error makes me think he would only settle for pretty good stuff, or might even have some data himself.

I would like to get around 30 of each type of sprayer, but my budget for togo's is only about $100, thats all I can spend on this stuff atm. I'll let you know how my cart gets split up and what sprayers I buy, and edit the first post above to show love-potion's and liquid alchemy's.

I'd like to get some regular sprayers too, but more and more I find myself making togos, especially when I make my own mixes. That and my limited budget mean I'll probably just be comparing togo's.

I don't really like making more than a few ml's of a mix at a time in case it turns out to be a bad mix, so I use togo's more often, and I think most peoplewho make their personal mixes tend use togos for the same reason.

(03-12-2012 10:56 AM)Fly So Hi Wrote: [ -> ]Jeez, 26 microlitres margin of error only in the needle?

The more i read, the more i convince myself i need a pipette.


Syringes, not pipettes, and thats only with the syringes from here:

This study is decent, though I kinda wish they would have used more than a measely 35 needles, and that they published the results of individual needles, not just groups. This is why I want a study of my own to find out exactly what goes on with that dead space.

I have yet to find data on similar products from other brands, but there's a special low wastage needle fitting for most brands.

But that brings up a good point, it could be possible to use pipettes, but it would be very difficult to automate the ones where you squeeze a bulb at the top. In general I have yet to find a pipette that comes close to the accuracy of a syringe, ut then again I have yet to really look much. I hav the androtics pipettes, and the pale in comparison.

Most of this is beyond the accuracy you'd need, but I figure that if one part of the system is weak (the sprayer for example), then it becomes all the more important to tighten up the other parts as much as possible. Eventually I'd like to get this info out so that users can specify the margin of error of sprayers and things like that. I mean if its 1mcg of some pheromone, but the margin of error brings it up even by 1 more mcg, you've already literally doubled your dose that time.
Also, if someone knows a way to get the bottles more directly (from wherever the vendors get them), that'd be very helpful, because it would probably cost less and allow me to test more bottles.
(03-12-2012 1:58 PM)gentlmentlemen Wrote: [ -> ]Also, if someone knows a way to get the bottles more directly (from wherever the vendors get them), that'd be very helpful, because it would probably cost less and allow me to test more bottles.

I have several websites to get bottles not sure about the which the vendors use
(03-12-2012 3:31 PM)shadowknight Wrote: [ -> ]I have several websites to get bottles not sure about the which the vendors use

Thanks a bunch. Still have a lot of looking to do, but just off a quick glance:

This looks awfully familiar.

Maybe I should contact the vendors and ask them exactly which bottles they use, just to be certain.

On my way to do that now.
Can anyone comment on whether these are any good?

Geez these things can get expensive...

I need at least .001g accuracy though, because 1ml of water is ~1g in weight (depending on room temperature, height above sea-level, etc), so to measure things like the .026 ml syringe dead space, I would need at least .001 grams accuracy. It looks like there are a couple scales there that fit my budget, but if I could get more accuracy while still staying close to my budget that'd be great.

More importantly... if I were to buy the $65 or $50 ones, would they really be enough to do the job well? Because I see other scales there with much higher price tags but the same accuracy... maybe its just the range of weights they can handle that drives the price up, but I get the feeling that they have the descriptor of "analytical" for a reason.
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