Voltmeter reads 16 at speed?

[skyguy.r]

Earlier in this thread I mentioned my gas gauge was misbehaving. Well, I replace it. It is of the type with a float on an arm which is connected to a variable resistor. For the moment, let’s assume I set the arm length just right. (I would have used a reed switch sensor but I could not find one for a 4 inch deep tank.) At the higher RPMs, when the voltmeter is reading around 16 Volts, will the gas gauge be off by 16/12[SUP]ths[/SUP] or 12/16ths or not effected by battery voltage?

 

[sam am I]

According to my math models, It should be about a plus 33% error, so yes, 16/12th error when varying the supply voltage from 12V to 16V

This is of course assuming the gauge itself has no internal regulation and/or compensation circuity for varying supply voltages and is strictly a dumb linear device........I'd hazard a guess that some off the shelf $21.99-$59.99 auto-zone auto meter lesser expensive types could be.

But, thinking a zener diode is a pretty cheap clamping device to slap in to form a sorta decent fixed reference/regulator internal to the gauge, so it could be a crap shoot depending on the manu, so as a test...........

and In theory then to find out you should be able to note a particular level w the engine off and just sitting still, then start the engine and still sitting still, rev the motor up to around the 16V'ish from 12V'ish and see the needle move up and down quite clearly w a possible 33% error as you start up and rev it up and down eh?

I do recall back in the day seeing the occasional needle (not voltage :facepalm moving around a bit as the engine rev'd, not sure where and who's thou, just think I saw it happen here and there. Maybe it was my parent's 1962 VW Bug





Lower traces show calculated unregulated voltage extents at sender signal out as seen by/at the gauge's input from empty tank(highest levels) to full tank(lowest levels)

Top traces show percent error. given by.......

Percent Error = [experimental value - theoretical value] / theoretical value x 100%

 

[14.4volts]

16v is like using a quick charger, it may be close to boarderline for some 12v equipment (doubtful), a lot have a operational threshold of 12~16/18v, my guess is that your max output is 16v with a quick bleed off, have you done as suggested and added an extra load?
If your really worried you could get a cheap external regulator for next to nothing and add it inline between your isolator/switch, I think I've seen ones for mopeds for about $5 on amazon, just make sure your matched with MAX amp output of your motor.
remember also that a lot of regulators require a load before operating.

Have you checked your meter against say your car? cheaper multimeters and gauges have (I've seen) a threshold of up to +/-5% and that would be .8% which would be 15.2v, also I would check your actual AMP draw or output to your battery, if its 16v @ 1amp itll take along time to over charge it from starting.
I would think your engine underway would create sufficient load to drop your voltage down, fully charged battery rests at around 12.5/.6v with atleast 70% charge, and can read into the 13s if tested immediately after charge, your cars regulator charges @14.4v when under load and drops to 13.5ish when floating, id turn on your running lights and see what the gauge reads, if your charging at over 13.8v with a load on the battery and no regulator you will eventually cook it.