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Fuel level gauge


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I have done some googling and can’t find any answers, so here I am again. 

I have smiths flight gauges and they all work perfectly. The fuel gauge is a little too keen however. In the corners as the fuel sloshes side to side the needle reacts instantly and swings all over the place. It’s all set up correctly but needs smoothing or dampening. Has any one else had any luck with this problem? 

 

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 Smiths flight gauges

Not sure if this may help but some Smiths gauges were wired to a 10v voltage regulator to give the gauge stability in operation.

Fuel level, Water temp & Oil temp.

I am not sure about the new gauge wiring but would be good to check if this helps.

Regards Martin

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Regulation wouldn’t help but thanks for the idea. It’s not a voltage problem it’s a fuel level going up and down like an yo-yo problem. There are numerous mechanical methods of fixing the problem but it’s more trouble than it’s worth.  Don’t spend a pound to save a penny sort of a thing. 

I want to try a hand full of simple ideas and will let you know the outcome. 

I think ultimately I’ll end up decoupling the feedback via some sort of sampling circuit, just hoped that someone would say ‘‘yeah but this for £10 off eBay and you’re done’’. 

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Some flight gauges had a damper issue, I understand its a circuit in the guage, and can be adjusted.

Problem is getting into the guage is destructive, but Smiths (CAV) did do a few FOC, have a word with them, may depend on where you got them and how long you have had them

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Try http://www.spiyda.com/?SID=fcdc1f758f8c29feb12928e22b7d1411 Chris is very good if he hasn't got what you want he may make it up for you, I'm on my phone so can't see if he does what you want but I think so. Please make sure you get the I & the y the right way around it you end up with a very different website 😂😂😂😂

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we crosses posts nicely there  they seem a good company. I’ll do a bit of pondering for now but that would make life easy  

 

I have thought about adding a damper weight around the pivot point of the arm in tank. Significantly raising the moment of inertia wouldn’t allow the float arm to move rapidly, but it would still move freely. It would need to be finely balanced and centred to avoid misreading tho. 

Edited by Mrbarry
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Had an email from smiths today. They said send the gauge in and they will mod the software on it to add dampening. The fuel gauge should be dampened but apparently sometimes they assign none dampened software to them. It could be £25 but if it turns out it has the none dampened software (it does) it will be a free alteration.

Either way they can sort it with no need to add extra parts or alter a thing. Peter the software engineer was very helpful tbf. 

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There's software in a fuel gauge? Surely they are all just a bit of basic voltage-sensing electronics? Software suggests a chip, transformer to get from 12v to 5v  etc, etc...

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I'd imagine a lot of stuff is logic ICs and software-driven these days. The ICs are not much more expensive than the equivalent passive components and you can then make a common board for a variety of functions/clocks, and just control the operation and features via software. You get slightly more complex design and production but you've got so much more flexibility at the hands of programmers, and future-proofing/etc.

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Exactly that. Mass production has made micro processors so cheap and common place you get them everywhere. 

As ive probably posted I’m an electrical engineer and have dealt with a huge array of kit in my 27 years in the field, it is constantly changing and developing. It’s so cheap and easy for a company pluck a programmable integrates circuit off the shelf to do whatever you need these days. Electronics I don’t do, but I have an appreciation of the subject as you would imagine. Few people appreciate the size of the field that is electrical control, each area has specialists and experts. 

I do know smiths, like many others, use a single board and simply swap the face, bezel, fingers, etc, then program the thing to do as they wish. Stepper motors are precise and efficient and it makes perfect sense. They could make any custom gauge you like from this single base. That’s not to say all of their gauges are identical they do make none stepper motor ones but again minimising parts and sharing enables even more bulk buying power for them. It just makes sense. And ICs can be powerful now, even tiny ones can carry massive processing power with all sorts of custom algorithms built in right from the factory. 

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