Level measurement problem
Level measurement problem
(OP)
I've run across an interesting continuous level measurement challenge. I need to measure the level of a mixture of Aluminum Oxide and ceramic powder, inside a closed vessel (approximately 48" high), that is kept under partial vacuum. Ultrasonic sensing is no good, because of vessel not being at atmospheric pressure (speed of sound different). If the vacuum was constant, I could apply a correction factor, but it isn't. Capacitive level sensing won't work, because the conductive powder will stick to the probe. I don't know if an RF-type level transmitter will work, never having worked with one, and the department paying for this project is reluctant to part with $$$$ for experiments. Any ideas would be appreciated. Thank you.





RE: Level measurement problem
Hope this helps..
MadKungFu
RE: Level measurement problem
Can you use a float-type device? Or, perhaps a sensor that drops down, contacts the material, then raises? The latter isn't quite continuous, but I've used it in a similar situation (much larger tank).
I once used a "tuning fork" device as a level switch. They (Endress + Hauser, I think) may make a continuous device. Since it vibrates, I don't think the vacuum would affect it.
RE: Level measurement problem
with >2 dielectric constant -- measure capactance if the
composition of the mixture is constant.
<nbucska@pcperipherals.com>
RE: Level measurement problem
saxon
RE: Level measurement problem
I like saxon's radar suggestion. Suggest you check out and/or call Ohmart-Vega.
RE: Level measurement problem
sticking powder away.
<nbucska@pcperipherals.com>
RE: Level measurement problem
vibrating probe or rotating paddle type sensors are commonly used for solids level in control and alarm functions. Cheap and reliable.
Load cells are used where more precise measurement of the quantity is needed.
cap probes are a non-flyer in the service your are describing. radar might work but you'll have to try it; there are more details involved in a proper installation and with a single point probe. Forget nuke meas.
RE: Level measurement problem
Thanks, HM
No more things should be presumed to exist than are absolutely necessary - William of Occam
RE: Level measurement problem
http://www.omega.com/literature/transactions/volume4/T9904-14-RAD.html#rad_4
TTFN
RE: Level measurement problem
"You get what you pay for." (anon.)
RE: Level measurement problem
i beleve for ur process paddle type level switch may be comfortable if the temperature is not too high enough.
RE: Level measurement problem
RADAR type level transmitter can be a better option, if at all you want to measure the level.
Believe it or not : Had we trusted Archimedes and assigned him the work of lifting the earth(or any mass equivalent to that of earth on earth),with a lever of suitable length, it would have taken him 23 million million years to lift the earth by one centimeter, if he worked at the rate of 1 HP.
RE: Level measurement problem
you should be able to make a load cell solution at approx half the stated 600$ price.
Use only one load cell.
Best is to suspend the entire vessel from one point (no calibration required).
Second best is to make a stand where the load is pivotted in one side, and placed on the load cell in the other side (as the load cell does not have 100 % of the load, some calibration and signal scaling will be required).
Shop around for load cells solutions. You should be able to get a reasonable deal if your precision requirements arent too stringent.
RE: Level measurement problem
John
RE: Level measurement problem
RE: Level measurement problem
Do you really think the guy needs an answer after half a year? :)