Arcangeli Enrico: Wiring of gas meter

Discussion in 'OnBoard Electronics & Controls' started by akoako, Apr 7, 2015.

  1. akoako
    Joined: Apr 2015
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    akoako Junior Member

    Hello all,

    I just realised the the wiring to the petrol tank is not connected to the meter in the cockpit. But looking at the back of the meter I am lost where to put the wiring from the tank. Do you have any idea?

    All ideas are appreciated!

    Achim
     

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  2. BertKu
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    BertKu Senior Member

    I see it is a multiple task meter. What else does it give you apart of the status of the petrol tank?
    Bert
     
  3. BertKu
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    BertKu Senior Member

    Guten Tag, You could do it in the elimination way. switch your main switch on and then remove one by one the connector.(Except earth) Those which are not the petrol gauge, cross them of your list . What is leftover can only be the petrol tank. Just measure the wire(s) from the petrol tank, so that you connect them correctly if it is more than 1 wire. (you may otherwise short circuit something) Also maybe the plus red wire to the plus, you should not remove. Bert
     
    Last edited: Apr 7, 2015
  4. akoako
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    akoako Junior Member

    Thanks already! Yes it is a multiple meter. It also shows temperature - if I remember correctly, I'm going to check tomorrow.

    Currently it always shows a full tank, the 2 wires from the tank are not connected at all.

    Probably I have to follow your advice and do it the elimination way...

    Achim
     
  5. akoako
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    akoako Junior Member

    I did it by trial and error and it looks as if it might be working working:)

    But: With an empy tank it show 3/4 quarters in the meter. Could it be so easy as to put an additional potentiometer before or after going to the tank?

    Best regards!

    Achim
     
  6. BertKu
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    BertKu Senior Member

    Sorry I was in Sutherland, the coldest place of South Africa , where the International Telescope is located, had no means to reply to you.

    I understand now, that your empty tank is now a different tank and a new empty tank? is this correct? If that is the case , yes a WIRE WOUND potentiometer could possible be doing the job. However it is not that easy. The resistance of your "TANK resistance" means that your voltage and resistance is not matching.
    Please measure the resistance of your tank "sliding resistance" with a multimeter and let us know what the resistance is in, full, half full and empty position. Also tell us what the Voltage is, applied to the "tank sliding resistance". We can then make a plan.
    Bert
     
  7. BertKu
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    BertKu Senior Member

    Hi there,
    You have to make sure that the earth connection is a proper low resistance connection. Better is it, to make sure that all connections are free from oxidation.
    Bert
     
  8. akoako
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    akoako Junior Member

    Hi,

    thanks for your reply. You're right, the resistance of the tank does not fit to the meter.

    I measured the resistance for the following 2 filling levels (The capacity of the tank is 60l):
    20l resistance is 90 Ohm, the meter is between 3/4 and 4/4.
    40l resistance is 60 Ohm, the meter shows already more than 4/4

    I would try a potentiometer in the range up to 100 Ohm and then do manual calibration. What do you think?

    Greetings to south africa!

    Achim
     
  9. BertKu
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    BertKu Senior Member

    Hi Achim, thanks, South Africa wish you a pleasant summer, while we are going into the winter.

    You are getting on the right track.
    120 Ohm = 0 liter (Please confirm this to yourself)
    90 Ohm = 20 liter
    60 Ohm = 40 Liter
    30 Ohm = 60 Liter (Assumed that the fuel sliding resistance is linear.
    I bet with you that the meter has a shunt resistance which is parallel over the small ?? 100 miliVolt meter. You could adjust the shunt resistance, but that is asking for trouble.
    Your guess to place a 100 Ohm wire wound linear potentiometer in serial is a good step in the right direction, but you will most likely also have to have a 81 or 100 Ohm resistor parallel over the fuel sliding resistance to compensate.
    The wattage should be more than 2 watt, preferable a 5 watt resistor, otherwise it may get too hot. Also the extra wire wound potentiometer may have to be greater than 1 or 2 watt.
    Achim, you did not give us the voltages over the various components, thus we are guessing now. Good luck.
    Bert
     
  10. AndySGray
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    AndySGray Senior Member

    Take care on this one,

    There are actually two main 'standards'

    one goes 0 to 90 and the other goes 73-10 (i.e. backwards).

    I had this problem when I fitted new gauges - IIRC old ones were Faria and new were VDO.

    Old senders did not play well with new gauges.... :(


    I also had some fun with a spurious chinese branded sender and gauge 'kit'
    The sender had a rail which you cut to half tank depth plus 1 inch, then there was a sensor with a long lever which you cut according to a formula based on the depth then screwed a small float on. The sensor had a 'this way up' arrow - and all was as per the instructions / diagrams. We were in a time pinch so we threw some fuel in, I 'bench wired' the gauge - half full, all good, so while my colleague glassed in the new floor, I did the permanent wiring and fitted the gauge in the console. As we ran the boat I watched as the tank got fuller throughout the day :confused: Damn


    Back at the dock I re-read the entire instructions and all was correct, but I spotted a line in the 'troubleshooting' table -

    Gauge work backward - sensor arrow must be fit point downwards

    My colleague thought it hilarious 'till I pointed out we'd need to remove and reglass his nice new floor - much less amused then. I re-read the entire instructions and the ONLY mention of the arrow was in the Troubleshooting.

    :idea: Was our own work boat so the fix was much simpler - make an E and an F with a Dymo labeler and stick on the gauge with the F on the left :D

    ;)
     
    Last edited: Apr 21, 2015
  11. AndySGray
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    AndySGray Senior Member

    The flip side is that senders are actually quite cheap (and provided your colleague has not glassed it in :rolleyes:) quite easy to change. That looks like a really nice original gauge - so changing the sensor is a good option vs. new gauge.

    Have you got the old tank sensor to check the range?
     
  12. BertKu
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    BertKu Senior Member

    Hi Achim

    Refer to the previous reply:

    "but you will most likely also have to have a 81 or 100 Ohm resistor parallel over the fuel sliding resistance to compensate."

    Do not use a potentiometer. If you turn accidental this to the wrong side ( zero resistance side) and your other potentiometer is turned to a low value, you may damage your fuel meter.


    Bert
     

  13. BertKu
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    BertKu Senior Member

    Hi Andy,
    I did not get the impression that the meter from him was turning backwards, only exceeded the maximum value. He could decrease the shunt resistor, which is normally placed over most meters, whether it is a current meter, a fuel meter or whatever meter. But it would mean fiddling around with resistance wire, which not everybody has at hand. If he decreases the shunt resistor, the milli Volts over the two points will be lower and the meter will show half, when the fuel gauge is getting a lower milli Volt value. He could decrease it by placing a few meters of insulated wire parallel over the two points and then slowly cut the wire shorter until the full tank shows the full level on the meter. For me it is simple, I would measure what voltage is over those two points when shown full. Thereafter I would make a decision, how much wire I would cut and place over the two points.
    Bert
     
    Last edited: Apr 22, 2015
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