"Averaging" fuel level sender??

[wipe_out]

Are there any "averaging" or "damping" fuel level senders that don't send the fuel needle crazy??

In all but calm water my fuel gauge us near useless because it swings so wildly I have no idea how much fuel is in there..

 

[nigelmercier]

I think not in the sender (mine isn't at least), but in the display unit. Do you know the make and model?

 

[wipe_out]

I know the gauge is made by Faria but that's about it.. The sender is the standard float based one..

I have seen there are all sorts of fancy senders now like "ultrasonic" ones but seems a bit "complicated" for a simple task and quite expensive too..

 

[nigelmercier]

Probably best to contact them, I doubt you can open the gauge display.
http://faria-instruments.com/index.php

 

[Lakesailor]

It is the gauge that provides the response. In motoring they are termed "ballistic" and "damped". (or they were, years ago)

 

[srp]

You might be able to do something with the sender, like attaching a flat plate underneath the float arm (ie in the fuel) that stops the arm moving up and down so freely.
Or on the gauge, maybe fit a capacitor in the signal connection from the sender. I have no idea what value you'd need but you'd need to know the resistance of the meter coils to start with. And you'd need a rough idea of the sort of time period of the meter oscillation, then maybe T = R C ??? Can someone else more knowledgeable check this and comment please?

There is a diagram of the internals of a typical gauge here http://www.tb-training.co.uk/MarineE10.html#Types of Sender Unit which might help you or someone else to decide if a capacitor would smooth out the fluctuations.

 

[wipe_out]

Thanks for the information and thoughts.. I am probably going to pull the sender soon anyway so I can test it to make sure it's giving a smooth response across the range.. I will then also know what the resistance range is.. Perhaps then someone can help with the "damping" because my knowledge of electronics and components is limited..

 

[nigelmercier]

Or on the gauge, maybe fit a capacitor in the signal connection from the sender...

It would need to be huge. The gauge should have some form of damping, the manufacturer would be the best to advise.

 

[cimo]

The (floating arm?) sender is likely to be of the 240ohm variety, varying from 0ohm (tank full) to 240ohm (empty) - or the other way round - I'm not intimate with Faria. The sender is purely resistve, so it doesn't send a signal as such, its a current sink.

Thinking out loud, you could dampen the response electronically - essentially a resistance to voltage conversion, then a voltage rise time delay, followed by a voltage to resistance conversion to drive the guauge. The circuit would be active, requiring its own power, so probably alot of effort for relatively little gain imo.

Alternatively, and much easier to try out, place additional resistance in seriers with the sender. it won't eliminate the swinging entirely but will reduce guage sensistivity. Note: You must place an equal resistance in the other side of the guage circuit to maintain current balance and an accurate readout.

Get some 500ohm resistors - pennys from Radionics - & try the following -
125ohm, 4 x 500ohms resistors in parallel - to slightly reduce sensistivity.
250ohm, 2 x 500ohm resistors in parallel - reduces the sender influnce by half.
500ohm - a single 500ohm resistor - greater reduction in sensistivity.

you'll need a total of 8 x 500ohms resistors to try all the above.

You could also reduce sensistivity mechanically by introducing baffels to your tank, although I'm not sure how pratical that would be.

hope this made some sense!

 

[nigelmercier]

hope this made some sense!

Not really, adding resistors will reduce the range, not the damping.

 

[cimo]

Not really, adding resistors will reduce the range, not the damping.

Aim is to increase damping - not reduce.
To do this electronically would be fustrating for someone who has limited electronic knowledge as the OP has stated.

So, a 2nd best (and much much easier) approach would be to reduce sensistivity.
Full range will be maintained if both sides of the guage are modified to the same extent (see note in post #9).

We had some previous success here (although a different issue, the fix is easy enough, the resistances are added external to the guage i.e. no need to dismantle anything).
http://www.ybw.com/forums/showthread.php?229688-Wiring-fuel-gauges&highlight=cimo

 

[nigelmercier]

We had some previous success here (although a different issue...

That was a totally different scenario, where there was indeed a problem with resistance. The answer here is not to try to fudge it with resistors, but to find out why the internal damping is not working. Also, your resistor values in #9 appear to be arranged homoeopathically.

 

[Lakesailor]

I found a discussion about this issue on an American forum.
One poster claimed that some manufacturers used silicone on the needle pivots to slow down the movement.

 

[maxi77]

They used to do this in cars with gauges which operated by heating a wire in the gauge so oscillations of the sender were very effectively damped, it used to take several minutes for the gauge read properly after the ignition was switched on

 

[cimo]

That was a totally different scenario,

correct. (do you actually read the posts Nigel!, see last line post#11...."although a different issue, the fix is easy enough").

 

[srp]

I'm afraid I can see no way in which adding resistors would affect the sensitivity of a gauge of the type I linked to in my earlier post (ie the type with two coils). Ohms law doesn't have T in it. The only way would be to add capacitance, and as Nigel has pointed out the capacitors would need to be very large.

This leaves mechanical methods already suggested, or maybe change the sensor to a vertical sliding float type and mount it in the tank within an open ended tube (like gutter down pipe) to stop the fuel sloshing about. The other possibility is that the gauge should actually have its' own internal damping (maybe friction or oil) but it's knacked, in which case a new gauge will sort it out (just make sure you get one which matches your sender, ie US or Euro).

 

[wipe_out]

I don't fully understand the capacitance/resistance discussion so can't really comment..

The mechanical damping in the tank with a tube I do understand.. So if the sender is a probe type I might try that (just need to find a fuel safe pipe to use).. If the sender is a "arm" type then obviously that's not going to work so might need to replace the gauge in that case if I can find out whether they have damping built in.. No point replacing the gauge if its the same..

All this hassle just to try and get a more accurate idea of how much fuel is in the tank.. Last thing I need is to be running out..

 

[nigelmercier]

correct. (do you actually read the posts Nigel!, see last line post#11...."although a different issue, the fix is easy enough").

I think you will find that not only did I read it, but I quoted you. I just don't think a kludge is the best way forward. The best solution is for the OP to contact the manufacturer.

 

[srp]

I don't fully understand the capacitance/resistance discussion so can't really comment..

The mechanical damping in the tank with a tube I do understand.. So if the sender is a probe type I might try that (just need to find a fuel safe pipe to use).. If the sender is a "arm" type then obviously that's not going to work so might need to replace the gauge in that case if I can find out whether they have damping built in.. No point replacing the gauge if its the same..

All this hassle just to try and get a more accurate idea of how much fuel is in the tank.. Last thing I need is to be running out..

I'm thinking of the type shown here:
http://www.asap-supplies.com/marine/dip-type-tank-level-senders
You'd need to put a multimeter across the terminals of your existing sender to check for US or Euro model. Good description here http://www.asap-supplies.com/marine/senders-and-fittings.

Have to agree about running out of fuel. My existing tank is opaque, with no easy way to fit an electrical gauge and no way of dipping it, so I bought another (semi-clear Vetus) one at Beaulieu boat jumble the other day for £15, which was cheaper than buying the fittings to put in a sight tube. Much better than the risk of overfilling, and very much better than running out!

 

[cimo]

I don't fully understand the capacitance/resistance discussion so can't really comment..

All this hassle just to try and get a more accurate idea of how much fuel is in the tank.. Last thing I need is to be running out..

PM me your email if you like, I'd be happy to send a schematic (i've little attachment bandwidth left here).
You'll get the improvement you need with minimal time & cost.