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Volume Measurement (Dry Method)

by TechFan
Tags: measurement, method, volume
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TechFan
#1
May10-14, 07:06 AM
P: 34
Hi:

I have been working in this Project for a while now and I would like to share the results with you. Still needs some improvements; but it appears to be working fine so far. Please let me know your suggestions and ideas.
Thanks.
https://www.youtube.com/watch?v=OwI0EfT3fg8
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UltrafastPED
#2
May10-14, 07:19 AM
Sci Advisor
Thanks
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P: 1,908
To help with the pressure leakage: use a cylindrical chamber for the testing, with an o-ring and a groove for the pneumatic seal - similar to those used in vacuum chambers. A small bit of vacuum grease on the o-ring will improve the seal by "evening out" any small irregularities.
TechFan
#3
May10-14, 07:24 AM
P: 34
Hi:
Really thanks. I'm already building a Pressure chamber very similar to your description. Will post soon...
Thank you so much.

RocketSci5KN
#4
May12-14, 01:04 PM
P: 163
Volume Measurement (Dry Method)

Hi TechFan,

Very clever. For the accuracy checks, I would test machined cubes or cylinders with volumes that can be precisely measured. When filling with pressurized air, realize the air temp can be quite different from RT, at least initially. I would add a temp sensor inside to tell you when the air is very close to RT, and then start the test. Or, run the air through some form of heat exchanger to get it to match the RT. As noted before, use say an acrylic tubular housing, with o-rings on the top cap. Keep the pressures way below what this stucture can handle. The bottom can be sealed tight with acylic glue. A fun counter test would be to pull a vacuum within the chamber and measure the flow of RT air INTO the unit. This assumes the test unit won't be affected by vacuum. Again, make sure the design of the housing can handle vacuum without imploding.
TechFan
#5
May12-14, 03:19 PM
P: 34
Hi:
Thanks for your comments and suggestions. Right now I'm working on most of the things you have mentioned. The main goal so far was to test if the concept could work. The main problem is hardware improvements cost real money and not just my time on this. I already have the new Chamber (leak free) built with help from a machine shop and a some "greenbacks", working on another sensor to be placed inside the chamber as I want to monitor temp behavior right in there and also improving the GUI to perform leaks tests also. I'll post an update soon.
These are the sensors I'm using. I'll place another LM35DZ inside the chamber (trying)
-For Pressure Honeywell SSCDRNN250MGAA5 datasheet (http://sensing.honeywell.com/index.p...ment/1/re_id/0)
-For temp LM35DZ (http://www.ti.com/lit/ds/symlink/lm35.pdf)
Thank you so much.
UltrafastPED
#6
Jun2-14, 12:38 PM
Sci Advisor
Thanks
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P: 1,908
How are the sensor leads passed through the pressure chamber walls?

These work well for vacuum systems, though they leak if you crack the ceramic!
http://www.mdcvacuum.com/DisplayCont...d-bd5622ccaa5f

To install a suitable hole is made in the machine shop, and the electrical feedthrough is welded in place.
TechFan
#7
Jun2-14, 01:27 PM
P: 34
Hi:

Well at the moment I made the video there were no sensors in the Pr chamber. The Pr Sensor is installed in the hose coming out of the container (the Pr is the same). The temp Sensor is placed in the PC Board next to the Pneumatic System where it can measure the temp of the ambient air which is fed to the container. At this moment I had a Pr Chamber manufactured at a machine shop and I added another temp sensor to it by threading it in a threaded hole I made in the metal used for the Chamber.

Thanks


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