[DeTomaso] Fuel Gage Linearizer
Thomas Tornblom
Thomas.Tornblom at Hax.SE
Sun Nov 2 10:48:34 EST 2008
If anyone is willing to make and distribute the correctors, I'd be
happy to donate the work I've put in to it.
I like to design stuff, but I get bored quickly ;-)
Thomas
2 nov 2008 kl. 06.21 skrev "Tomas Gunnarsson" <guson at home.se>:
> There's more info on Thomas' web site;
>
> http://www.detomaso.nu/~thomast/gauge-corrector/
>
> Tomas
>
> ----- Original Message -----
> From: "John Taphorn" <jtaphorn at kingwoodcable.com>
> To: "Edward A. Nauman" <enauman at roadrunner.com>; "Email Forum
> Pantera" <detomaso at realbig.com>
> Sent: Sunday, November 02, 2008 2:42 PM
> Subject: Re: [DeTomaso] Fuel Gage Linearizer
>
>
>> Ed
>>
>> Several years back, Thomas Tornblom offered his electrical
>> engineering
>> expertise to the group with an alternative solution he called his
>> Gauge
>> Corrector.
>>
>> It is an adjustable eeprom to match the sender to any gauge. If I
>> recall
>> correctly, the eeprom can store 10 data points. Thus, I was able
>> to adjust
>> my fuel gauge to read accurately at 1/8th intervals by filling the
>> tank 2.65
>> gals at a time and storing the value. Of course, it assumes that the
>> quantity of fuel used between those data points is linear for a
>> given drop
>> in the float arm. However, accuracy at 1/8th intervals is close
>> enough for
>> me. Obviously, if you are using a data point for every gallon
>> verses 2.65
>> gals, your approach will be more accurate between my 1/8th data
>> points.
>>
>> Although a benefit of Tom's eeprom approach is that I was able to
>> calibrate
>> it myself and could easily perform the operation again should I
>> change my
>> gauges to a set with a different impedance. I.E. I am currently
>> using it on
>> my Auto Meter, but could have used it on my Veglia initially.
>>
>> I don't know if Thomas is still offering the product. It was very
>> inexpensive and has the JT Seal of Approval.
>>
>> I am not trying to discourage your idea or willingness to help,
>> simply
>> illuminating the possibilities and the contributions of others.
>>
>> JT
>>
>>
>> ----- Original Message -----
>> From: "Edward A. Nauman" <enauman at roadrunner.com>
>> To: "Email Forum Pantera" <detomaso at realbig.com>
>> Sent: Saturday, November 01, 2008 1:56 PM
>> Subject: [DeTomaso] Fuel Gage Linearizer
>>
>>
>>> Hi guys,
>>>
>>> I have been away from the list for a while and was searching
>>> through
>>> the archives. I came across a message about a circuit I designed
>>> a couple
>>> of years ago. Being an instrumentation engineer for 3 decades,
>>> one of my
>>> pet peeves developed over the years is the non-linearity of
>>> automotive
>>> fuel
>>> gages. The fuel gage in most cars is really a fuel level gage and
>>> not a
>>> fuel quantity gage. Since the fuel level transducer is usually a
>>> wire-wound
>>> potentiometer actuated by a float at the end of an arm, the
>>> potentiometer
>>> output is proportional to the angle of the float arm which is a
>>> sinusoidal
>>> function. Most of the automotive fuel level pots I have examined
>>> have a
>>> linear output with respect to rotation angle of the shaft. So,
>>> the fuel
>>> level with respect to the output of the potentiometer becomes a
>>> function
>>> of
>>> the length of the float arm and the sin of it's angle. In other
>>> words the
>>> measurement, if uncorrected, is non-linear. This is sometimes
>>> corrected
>>> for
>>> by manufacturing a non-linear pot that linearizes the sinusoidal
>>> output in
>>> the range of interest. Remember, that is for fuel LEVEL. When you
>>> translate level into quantity. The shape of the fuel tank becomes
>>> the next
>>> source of non-linearity. Obviously if you had a cone shaped tank,
>>> one
>>> inch
>>> of fuel level near the top is a lot more than quantity 1 inch at the
>>> bottom.
>>> Depending on the irregularity of the cross-sectional area of the
>>> tank as
>>> the
>>> fuel level rises, the equation for quantity Vs. level can get quite
>>> complicated. The simplest way to correct the situation and still be
>>> adaptable to different tank shapes and sizes is to use a micro-
>>> controller
>>> and a calibrated look up table to translate the level into actual
>>> quantity.
>>> The design I came up with for my car uses a PIC microcontroller
>>> that has
>>> on
>>> board an EEPROM to store the look-up table. Operationally, the
>>> fuel level
>>> potentiometer is connected to my circuit which reads the
>>> resistance and
>>> "looks up" the correct corresponding fuel quantity. It then drives
>>> the
>>> gage
>>> with the correct voltage to indicate the actual quantity. The setup
>>> requires calibrating the tank at 1 gallon intervals which means
>>> draining
>>> the
>>> tank and filling it one gallon at a time. Since I was only
>>> building one
>>> of
>>> these circuits for myself, I did not write any code to have the
>>> micro
>>> perform the calibration automatically, meaning, that I recorded
>>> ADC output
>>> on my computer, generated the lookup table with Excel and manually
>>> entered
>>> the lookup table into the micro. I did the same thing for the one
>>> I built
>>> for Chuck Buthala. But that meant he had to perform the
>>> calibration,
>>> email
>>> me the data, and I programmed his look up table and sent the box
>>> to him.
>>>
>>> If you guys are interested in something like this, I can do
>>> 1 of 2
>>> things. I can put together a kit consisting of a PCB and a parts
>>> list
>>> with
>>> a schematic and a wiring diagram. Or, I can build you one and
>>> send it to
>>> you with installation instructions. But unless you are familiar
>>> with PIC
>>> microcontrollers and own a programmer, you would have to send me
>>> the data
>>> and I would have to program it and send it back to you. In order
>>> for me
>>> to
>>> write the code for an auto calibration routine, I would have to have
>>> enough
>>> commitments to justify the time spent. Bear in mind, I'm not
>>> trying to
>>> make
>>> money here, just offering this to my Pantera brothers if they are
>>> interested. If there is enough interest, I will figure out a
>>> price based
>>> on
>>> the responses I get.
>>>
>>>
>>> Cheers,
>>>
>>> Fast Eddie (#2100)
>>>
>>>
>>> P.S. If my explanation is either too complicated or too simple,
>>> please
>>> let
>>> me know and I will clarify any questions you may have.
>>>
>>>
>>>
>>>
>>>
>>> Edward A. Nauman\
>>>
>>> C.E.O.
>>>
>>> Smart Litez Inc
>>>
>>>
>>>
>>> Palmdale, CA. 93551
>>>
>>> (661) 305-7636
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>> The circuit was designed by Ed Nauman. He built one for me and
>>>> it works
>>> great. The gizmo works with a chip which uses the sending unit
>>> resistance,
>>> compares it to a look up table in the memory and >sends the
>>> correct signal
>>> to the gage. You have to go though a calibration cycle to set it
>>> up.
>>> There
>>> is an article in the POCA news about two years ago on the
>>> circuit. Ed if
>>> your listening I hope my >description is correct.
>>>
>>>> "www.ProvaMo.com" <pantera007 at sbcglobal.net
>>> <http://list.realbig.com/mailman/listinfo/detomaso> > wrote: It
>>> was not
>>> "Me" Chuck that Ohm'ed, but I did test one gallon at a time, the
>>>> ohming was, I think, someone in the Nordic region perhaps.
>>>
>>>> Chuck
>>>
>>>
>>> -----Original Message-----
>>> From: detomaso-bounces at realbig.com
>>> <http://list.realbig.com/mailman/listinfo/detomaso>
>>> [mailto:detomaso-bounces at realbig.com
>>> <http://list.realbig.com/mailman/listinfo/detomaso> ]On
>>> Behalf Of Mark McWhinney
>>> Sent: Tuesday, July 24, 2007 10:41 AM
>>> To: 'Garth Rodericks'; detomaso at realbig.com
>>> <http://list.realbig.com/mailman/listinfo/detomaso>
>>> Subject: Re: [DeTomaso] Incorrect gas gauge
>>>
>>>
>>> Some of the fancier aftermarket gauges allow for multiple
>>> calibration
>>> points. I think little Larry has that. If he is lurking, may he
>>> can fill
>>> us in.
>>>
>>> As I recall, Chuck did the one-gallon at a time work to record the
>>> ohm
>>> readings.
>>>
>>>
>>> -----Original Message-----
>>> From: detomaso-bounces at realbig.com
>>> <http://list.realbig.com/mailman/listinfo/detomaso>
>>> [mailto:detomaso-bounces at realbig.com
>>> <http://list.realbig.com/mailman/listinfo/detomaso> ] On
>>> Behalf Of Garth Rodericks
>>> Sent: Tuesday, July 24, 2007 10:33 AM
>>> To: detomaso at realbig.com
>>> <http://list.realbig.com/mailman/listinfo/detomaso>
>>> Subject: [DeTomaso] Incorrect gas gauge
>>>
>>> Just another reference point for the non-calibrated nature of our
>>> gas
>>> gauges.
>>>
>>> When mine is full it registers Full.
>>> 40 miles after fill up it registers at the 3/4 mark, or slightly
>>> below.
>>> But I can drive for quite a long time between 1/2 tank and Empty.
>>> And, at Empty the warning light comes on.
>>>
>>> I have not tested how far I can go after the warning light comes on,
>>> however the most I've
>>> been able to add at a fill up was 19.5 gallons.
>>>
>>> Now, I recall a year or two back that someone posted that they
>>> made a
>>> simple electronic
>>> converter to calibrate the fuel gauge. I think they took ohm
>>> readings from
>>> the sender as they
>>> filled the tank 1 gallon at a time, then created a mapping table
>>> to send
>>> an accurate reading
>>> to the gauge. Does anyone remember who that was? I recall they were
>>> planning to make it
>>> available for sale, but I never saw anything more on it. Does
>>> anyone have
>>> more info? I'd like
>>> one.
>>>
>>> Cheers!
>>> Garth
>>> #4033
>>>
>>> YMMV,
>>> Garth
>>> #4033
>>>
>>>
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