Author Message
 mossige
 Posted: May 03, 2012 - 08:27 PM
 Joined: May 23, 2003 Posts: 544 Location: NAERBOE, Norway
 I am to build a capasitor: 3 strips of Al. 1.5mm x 22mm x 200mm.Monted at a distance of 1 mm. This should give 1000 pF in fre air. Diesel, fuel, have an dielectric constant of 4, giving a cap. Of 4000 pF. This oneI I will try to use as fuel level sensor: 1/5 – 2/5 – 3/5 – 4/5 – 5/5. (5/5 = 5 litre.) I will try CD4047 as fre runing multi vibrator. -> TN15 I wil get challenges. He fuel are made to a conductor! I wil try to compensate by anodize or give it a thin stroke of paint. I need warnings and good advice howto solve it. HM

 Jepael
 Posted: May 03, 2012 - 09:07 PM
 Joined: May 24, 2004 Posts: 5994 Location: Tampere, Finland
 Charge transfer (Qtouch) method would be easier than converting that capacitance to frequency with an oscillator.

 ka7ehk
 Posted: May 03, 2012 - 09:19 PM
 Joined: Nov 22, 2002 Posts: 12041 Location: Tangent, OR, USA
 Diesel is pretty hard on organic coatings. And, you DO NOT want the coating to dissolve into the fuel, as it could damage the engine. Jim _________________Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA "The only thing standing between us and victory is defeat" P.G.Wodhouse in Wooster & Jeeves series

 mossige
 Posted: May 03, 2012 - 09:53 PM
 Joined: May 23, 2003 Posts: 544 Location: NAERBOE, Norway
 Jepael wrote: Charge transfer (Qtouch) method would be easier than converting that capacitance to frequency with an oscillator. Thanks (?). Qtouch are a new word for me. Googel gave 2 hit; 1 suspected, 1 irelevant. Would you explain? HM

 mossige
 Posted: May 03, 2012 - 09:55 PM
 Joined: May 23, 2003 Posts: 544 Location: NAERBOE, Norway
 ka7ehk wrote: Diesel is pretty hard on organic coatings. And, you DO NOT want the coating to dissolve into the fuel, as it could damage the engine. Jim The diesel are for a heater, mot for a motor. HM

 krazatchu
 Posted: May 03, 2012 - 10:22 PM
 Joined: Dec 29, 2007 Posts: 499 Location: Ontario, Canada
 How about some foil tape along a length of hose... _________________Michael -- http://krazatchu.ca/

 mossige
 Posted: May 03, 2012 - 10:32 PM
 Joined: May 23, 2003 Posts: 544 Location: NAERBOE, Norway
 krazatchu wrote: How about some foil tape along a length of hose... I do not se what callange it should solve. Explain? HM

 nleahcim
 Posted: May 04, 2012 - 12:17 AM
 Joined: Feb 19, 2003 Posts: 2233 Location: Seattle, WA
 mossige wrote: Jepael wrote: Charge transfer (Qtouch) method would be easier than converting that capacitance to frequency with an oscillator. Thanks (?). Qtouch are a new word for me. Googel gave 2 hit; 1 suspected, 1 irelevant. Would you explain? HM First result on google: http://www.atmel.com/products/touchsolu ... fault.aspx

 Kartman
 Posted: May 04, 2012 - 02:45 AM
 Joined: Dec 30, 2004 Posts: 8760 Location: Melbourne,Australia
 There is also the issue of sparks etc that may ignite the fuel. http://www.esdjournal.com/static/Contro ... 0final.pdf

 mossige
 Posted: May 04, 2012 - 03:45 PM
 Joined: May 23, 2003 Posts: 544 Location: NAERBOE, Norway
 nleahcim wrote: mossige wrote: Jepael wrote: Charge transfer (Qtouch) method would be easier than converting that capacitance to frequency with an oscillator. Thanks (?). Qtouch are a new word for me. Googel gave 2 hit; 1 suspected, 1 irelevant. Would you explain? HM First result on google: http://www.atmel.com/products/touchsolu ... fault.aspx Yja. I se(?) You mean I should put some "Qtouch" into my capasitor. Of cauce you are right (?). I think I start with 1/10, ZIP-ed. HM

 Chuck-Rowst
 Posted: May 04, 2012 - 04:51 PM
 Joined: Jul 19, 2011 Posts: 460
 HM, Is this a school project or real world?

 mossige
 Posted: May 04, 2012 - 05:55 PM
 Joined: May 23, 2003 Posts: 544 Location: NAERBOE, Norway
 Chuck-Rowst wrote: Is this a school project or real world? It is real world. The CD4047 are ordered. Hope I get it at the end of next week. HM

 Chuck-Rowst
 Posted: May 04, 2012 - 08:03 PM
 Joined: Jul 19, 2011 Posts: 460
 HM, Is this for a product to be mass produced and marketed? Or, is it for some kind of in-house/one-of-a-kind test equipment or process control system? You are dealing here with a class of electronics which comes under the umbrella of "Intrinsic Safety". A place where electronics (and the possibility of sparks and incandescing objects) meets flammable liquids and explosive gases or vapors. There are all sorts of industrial and insurance regulations in the USA and in the EU which govern this domain. You may recall that the 747 (Flight 800?) which exploded over Long Island, New York, in the mid-1990s was eventually attributed to a fuel tank explosion which was triggered by frayed wires associated with the fuel gauging probes in the tank walls. Jet fuel is essential kerosene ("paraffin" to you Brits)which is pretty hard to ignite in its liquified state, but combustible enough in its gaseous state which exists in the "empty" top part of the fuel tanks as the liquid fuel is consumed, that it can be set off by a relatively tiny electrical spark. Anyway, you may want to keep these regulatory limitations in mind before you get too far into your project. There are plenty of ways to design Intrinsically Safe circuits, but they generally need to be incorporated into the core design at the start of the project, not as blow-out patches at the end of the project.

 mossige
 Posted: May 04, 2012 - 08:49 PM
 Joined: May 23, 2003 Posts: 544 Location: NAERBOE, Norway
 Chuck-Rowst wrote: HM, Is this for a product to be mass produced and marketed? No. I wil build only one Quote: Or, is it for some kind of in-house/one-of-a-kind test equipment or process control system? It is for my eletric car, the heating system. My breath may colaps if I get cold aer into my lungs. Therefore, i can not go emty of fuel for the heater. Quote: You are dealing here with a class of electronics which comes under the umbrella of "Intrinsic Safety". A place where electronics (and the possibility of sparks and incandescing objects) meets flammable liquids and explosive gases or vapors. There are all sorts of industrial and insurance regulations in the USA and in the EU which govern this domain. I know. My son are working on those problems in thr oil industri out in the North Sea daily. HM [/quote{ You may recall that the 747 (Flight 800?) which exploded over Long Island, New York, in the mid-1990s was eventually attributed to a fuel tank explosion which was triggered by frayed wires associated with the fuel gauging probes in the tank walls. Jet fuel is essential kerosene ("paraffin" to you Brits)which is pretty hard to ignite in its liquified state, but combustible enough in its gaseous state which exists in the "empty" top part of the fuel tanks as the liquid fuel is consumed, that it can be set off by a relatively tiny electrical spark. Anyway, you may want to keep these regulatory limitations in mind before you get too far into your project. There are plenty of ways to design Intrinsically Safe circuits, but they generally need to be incorporated into the core design at the start of the project, not as blow-out patches at the end of the project.[/quote]

 westfw
 Posted: May 05, 2012 - 09:57 PM
 Joined: Jun 19, 2002 Posts: 950 Location: SF Bay area
 Quote: 1.5mm x 22mm x 200mm.Monted at a distance of 1 mm. This should give 1000 pF in fre air. The calculators I tried said 39pF...

 hugoboss
 Posted: May 05, 2012 - 10:42 PM
 Joined: Feb 19, 2010 Posts: 507 Location: Montreal, QC, CA
 Diesel does not ignite from a spark at room temperature and pressure. That is why diesel engines don't have spark plugs, they work by compressing the diesel and air in the cylinder to ignition temperature.

 Kartman
 Posted: May 06, 2012 - 12:49 AM
 Joined: Dec 30, 2004 Posts: 8760 Location: Melbourne,Australia
 Hugo, given the correct set of circumstances, diesel may ignite. Read my reference. In most countries there's mandated standards you must follow - for good reason.

 steve17
 Posted: May 06, 2012 - 11:01 AM
 Joined: Sep 07, 2004 Posts: 2522 Location: New York State
 Diesel fuel, like most petroleum products, is impure. I think it's a safe bet it will contain some more volatile petroleum components. Your nose will tell you of other impurities. The stink is from sulfur compounds known as mercaptans.

 JohanEkdahl
 Posted: May 06, 2012 - 11:09 AM
 Joined: Mar 27, 2002 Posts: 18540 Location: Lund, Sweden
 Quote: My breath may colaps if I get cold aer into my lungs. Therefore, i can not go emty of fuel for the heater. If this is about a project for a life-critical system, I would buy rather than build.

 Kartman
 Posted: May 06, 2012 - 12:05 PM
 Joined: Dec 30, 2004 Posts: 8760 Location: Melbourne,Australia
 Why not the old method of a toroidal float with a magnet in it riding up and down a sealed tube with reed switches in it?

 barnacle
 Posted: May 06, 2012 - 12:32 PM
 Joined: Jan 03, 2006 Posts: 4414 Location: Hemel Hemsptead, UK
 Given that (a) petrol has far more low-temperature volatiles than diesel and (b) fuel gauges have been safely driven by direct current through an exposed resistive wire and a sliding contact for about a hundred years in cars... why reinvent the wheel? I believe that aircraft use capacitive methods - a rod inside a tube with a small hole to vent will damp out splashing. _________________Neil Barnes www.nailed-barnacle.co.uk

 ana57
 Posted: May 07, 2012 - 08:10 AM
 Joined: Dec 16, 2005 Posts: 323 Location: Jyvaskyla/Finland
 Easy solution: Old fashion snowmobile fuel gauge, sensor is inserted to tube which is mounted to filling cap, also gauge needle is on top of filling cap. Can be inserted to small tank easily. Insert magnet to needle, measure needle angle with magnetic encoder, for example http://www.austriamicrosystems.com/Prod ... c-Encoders

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