Tank Depth
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From: Jim Thompson on 5 Jul 2006 10:57 On Wed, 05 Jul 2006 00:22:54 GMT, "James F. Mayer" <jfma(a)ix.netcom.com> wrote: > >"Jim Thompson" <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> wrote in >message news:r50ma2dsib6tk887j2p8r5522bq279j411(a)4ax.com... >> On Tue, 04 Jul 2006 15:50:22 -0700, "Paul Hovnanian P.E." >> <paul(a)hovnanian.com> wrote: >> >>>"James F. Mayer" wrote: >>>> >>>> I believe that a short time ago there was a discussion about this. but >>>> depending on the head of the tank one could use an MPX5000 series >>>> pressure >>>> sensor with a dip tube or am I too late? >>>> >>>> I have a number of 55 gal drums of water that I would like to know >>>> the >>>> depth of in my rain water gathering system so that I don't pump it dry >>>> and >>>> ruin a sprinkler pump. I am going to use one of them per drum to >>>> monitor >>>> the levels. I believe that the pressure of one foot of head is .43 PSI >>>> and >>>> that a drum is about 3 feet deep, giving a pressure of 1.29 PSI. Does >>>> this >>>> sound correct? >>> >>>That sounds about right. However ... >>> >>>This technique of measuring tank depth (quantity) may not work well over >>>a long period of time. In a washing machine, for example, the dip tube >>>only needs to maintain a reading for the duration of the fill cycle. I >>>suspect that slow leakage or air in the dip tube dissolving into the >>>water over longer periods (days, weeks) may reduce its accuracy. >>> >> >> That's the scenario I've been pondering. I'm trying to figure a way >> to measure (salt) aquarium level, for top off, that's reliable. >> >> I'm pondering a combination of washing-machine-style dip tube plus a >> (electro-mechanical) timer, to ensure that the tube clears before >> refill. >> >> Hopefully that would prevent false overfills due to air seepage from >> the dip tube. >> > > Running some of the aerator air through the dip tube would solve that >problem, I'd think. > Jim, Please elaborate, I'm not seeing what aerator air would do for you. Thanks! ...Jim Thompson -- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | | http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
From: Rich Grise on 5 Jul 2006 16:45 On Tue, 04 Jul 2006 22:36:28 +0000, James F. Mayer wrote: > > "John Larkin" <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in message > news:8fpla2hh5dfn7fq9gkrhgpelmnomkit93f(a)4ax.com... >> On Tue, 04 Jul 2006 21:55:16 GMT, "James F. Mayer" >> <jfma(a)ix.netcom.com> wrote: >> >>>I believe that a short time ago there was a discussion about this. but >>>depending on the head of the tank one could use an MPX5000 series pressure >>>sensor with a dip tube or am I too late? >>> >>> I have a number of 55 gal drums of water that I would like to know the >>>depth of in my rain water gathering system so that I don't pump it dry and >>>ruin a sprinkler pump. I am going to use one of them per drum to monitor >>>the levels. I believe that the pressure of one foot of head is .43 PSI >>>and >>>that a drum is about 3 feet deep, giving a pressure of 1.29 PSI. Does this >>>sound correct? >>> >> >> Yes. But what's a dip tube? >> >> John >> > > A tube that reaches to near the bottom of the tank/drum from the top. I wouldn't depend on a pressure sensor to be that accurate at the kinds of pressures we're talking about here. What's wrong with, say, a float switch, or maybe something like a sight glass with an optical coupler... Good Luck! Rich
From: Joerg on 5 Jul 2006 17:01 Hello James, > > ... I would like to also be able to > determine the amount remaining in the system if it isn't all pumped in the > time allotted. > Now that's more luxury than you mentioned at first. Some ideas that might or might not work in your case: a. A gas gauge mechanism from a car. Might corrode out over time. b. Sound transducers (old piezos, whatever) fastened to the side of the barrel at equal distances. You could use a uC such as the MSP430, a version with enough ADC muxes to excite and then scan them sequentially. This could also calculate the approximate contents and report in gallons, liters, jars, buckets, number of remaining toilet flushes or whatever is preferred. c. PVC pipe with end cap, must be absolutely water tight. Copper pipe in the middle that has an OD almost as large as the ID of the PVC pipe. Connect oscillator circuit to it. This forms a capacitor where the capacitance changes with the water level. This in turn changes the frequency but it won't be linear. Follow with a little F/V detection and you'd have a nice analog readout. Add a comparator that shuts off the pump below a chosen threshold. d. Stainless contacts inside, equidistant, with the lowest being the level where you want to pump to cut out. Connect to a stack of comparators a la LM339 and then to a row of LED. The lowest one deactivates the pump when the contact goes open. Of course, some of this depends on your water and other things. -- Regards, Joerg http://www.analogconsultants.com
From: Joel Kolstad on 5 Jul 2006 17:24 Joerg, "Joerg" <notthisjoergsch(a)removethispacbell.net> wrote in message news:uMVqg.166442$F_3.127811(a)newssvr29.news.prodigy.net... > c. PVC pipe with end cap, must be absolutely water tight. Copper pipe in the > middle that has an OD almost as large as the ID of the PVC pipe. Connect > oscillator circuit to it. This forms a capacitor where the capacitance > changes with the water level. You're using the container itself (55 gal. metal drum) as the other side of the capacitor... right?
From: Joerg on 5 Jul 2006 17:56
Hello Joel, >>c. PVC pipe with end cap, must be absolutely water tight. Copper pipe in the >>middle that has an OD almost as large as the ID of the PVC pipe. Connect >>oscillator circuit to it. This forms a capacitor where the capacitance >>changes with the water level. > > You're using the container itself (55 gal. metal drum) as the other side of > the capacitor... right? > That's what the other port would connect to. Here is a similar example: http://www.elecdesign.com/Articles/Print.cfm?ArticleID=11491 Although I would not do that with a monostable but with a regular LC oscillator. More stability, less drift (if built properly). -- Regards, Joerg http://www.analogconsultants.com |