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Sprayers, Scales, and Syringes
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Sprayers, Scales, and Syringes
03-12-2012 12:07 AM

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

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(This post was last modified: 03-12-2012 12:22 AM by gentlmentlemen.)
03-12-2012 12:07 AM
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Sprayers, Scales, and Syringes - gentlmentlemen - 03-12-2012 12:07 AM

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