Re: Measuring liquid level with bubbles using an ultrasonic transducer

[overgeo@xxxxxxxxx]

On 1 mar, 04:46, Marc_F_Hult <MFH...@xxxxxxxxxxxxxxxxxxxxx> wrote:
> On 28 Feb 2007 15:54:05 -0800, over...@xxxxxxxxx wrote in message
> <1172706845.461279.186...@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>:
>
>
>
> >Sorry for my late answer, i have been doing other projects. The liquid
> >is oil and is viscous, the accuracy is not a lot, the height of the
> >tank is 5 meter and an error of 10 cm is perfectly asumible.
>
> >So i can use a differential pressure transducer, with one transducer
> >that measures the pressure in the head of the tank and another one
> >that measures the pressure in the bottom of the tank, and with the
> >difference of both pressures i get the heigh of the liquid with this
> >formule h = differential pressure/(specific gravity * g)  where g =
> >acceleration due to gravity.
>
> >I have been looking for some sensors, and in this page there are some
> >of them.http://www.sensotec.com/pdf_catalog06/fp2000.pdf, the fp2000
> >wet/wet differential, i think will be suitable, what do you think?
>
> >To calculate the pressure range, i can use the formule.
>
> >max differential pressure =    h_max * (specific gravity * g),  is
> >this correct?
>
> >In addition the idea of the pipe was good, but i think that it will be
> >easier the differential pressure.
> >Finally thanks so much for all your answers
>
> I see that this is an industrial application, not home, so I recommend
> industrial components and mounting of the transducer outside the tank. This
> will better address the explosion hazard issues the specifics of which
> depend on the fluid, application and location.
>
> - Yes, that is the equation I provided, but see below for converting
> transducer output voltage directly to meters of fluid.
>
> - You said that the upper part of the tank would be under vacuum, thus the
> differential transducer.  The 5m of fluid water requires ~=500 millibar ~=
> 50kP  =~7.25 PSI. The nearest higher value offered by Honeywell/Sensotec
> seems to be the 10PSI   differential (~= 70kPa) But see below.
>
> - My preference is for 0-10vdc output assuming the associated electronics
> are nearby.
>
> - So with 10 PSI range and 10vdc Full Scale Output (FSO) the output is
> 1 PSI/volt = 0.701 meters of water /volt
>
> (You'll want to check my arithmetic! 14.7 PSI = 33.9 feet of water = 10.3
> meters of water. )
>
> For a fluid with specific gravity of n, the output would be (0.70/n)
> meters/volt output. For example, for an oil with a sp. gr. of 0.8, the
> output would be (0.70/0.8)= 0.875 meters oil/volt output.
>
> - The wetted materials of the Sensotec/Honeywell transducers
> (Hastelloy/lnconel C276 and 316SS) are suitable for any organic fluid.
>
> - You want differential wet/wet as I specified previously.
>
> - My preference would be for 1/4" NPT female fittings on the transducer
> because this facilitates connection to 1/4"OD x 1/8" ID stainless steel
> tubing using 1/4" SS-400-6  Swagelock fittings.
>
> I'd make a stainless steel flange and mount two SS-400-1-4BT Swagelock
> bored-through or SS-400-11-4  bulkhead stainless steel fittings on it and
> run the tubing through the fittings into the tank. The tube that goes to
> the bottom should be sealed (pinch it off) at the bottom and a slot cut in
> it a known distance up. This is so that you can set the tube to a known
> depth from the bottom (lower it as far as it will go)and still avoid having
> the input clogged with whatever debris may be on the bottom of the tank.
>
> Then connect the transducer _outside_ the tank at or below the level of the
> intake on the bottom with additional 1/4"x 1/8" tubing and SS-400-6
> swagelock union. Fill the lower tube with oil by drawing a vacuum on it
> until it siphons out oil from the bottom of the tank.. My preference would
> be to put a Nupro valve in each line near the stainless steel plate ( =
> bulkhead) so that I could remove the transducers without disturbing the
> tank.
>
> Hope This Helps ... Marc
> Marc_F_Hultwww.ECOntrol.org

Hi thanks and sorry for my late answers, your explanations are
excelent, thanks so much. I have revised your maths and right. I will
chose a 10 psi, but the output 4..20ma because the sensor will be far
(4 or 5 meters). My problems are with the positioning of the
transducer in the tank, i can't make an idea of how the transducer
must be placed.  Thanks again, and can i do something for you?