The Gas Gauge -an Analogy

Yes, the anemometer again.

An analogy occurred to me the other day, the low-fuel light in the car. When the car gets low on fuel a chime sounds and a light the shape of a gas pump lights on the dashboard. This is a signal that the fuel tank is getting low.

I’d argue that having a low-fuel level light [B]reduces the chances of running out gas.[/B] The reason why is because of the nature of the information.

Now say you have a car and low fuel light does not work. And you run out of gas.

Here is list of arguments that the low-fuel light could not have been a factor:

  • completely redundant, it doesn’t tell the driver anything that can’t be learned by looking at the gas gauge.

  • Fuel level can be determined with the odometer, the gas gauge is redundant.

  • Fuel level can be determined by knowing trip distance - the odometer is not needed.

  • Fuel level can determined with a putting a stick in the gas tank, they way we do it on the farm,trip distance is not needed.

  • Tank can be filled up by time, for example every so many hours / days. Knowing the level is not needed, only the passage of time needs to tracked.

And so forth. So, it’s 100% true that fuel level can be estimated without a low-fuel level warning.

However none of these arguments really refute the assertion that a low-fuel warning increases the chances that the driver will notice he is running low on fuel.

[QUOTE=Kennebec Captain;196011]However none of these arguments really refute the assertion that a low-fuel warning increases the chances that the driver will notice he is running low on fuel.[/QUOTE]

this is getting ridiculous…not having a working anemometer did not lead the EL FARO into peril. BAD DECISION MAKING ON THE PART OF THE MASTER LED TO THE LOSS. HIS NOT BEING ON THE BRIDGE AS THE VESSEL APPROACHED THE CENTER OF CIRCULATION IS WHAT KILLED ALL OF THEM!

Here’s what Earl says:

The situation with regard to assessing the location of the storm brings up the distinction between systems that are safety-critical and systems that are safety-relevant. A malfunction in a safety-critical system will generally directly lead to an accident (e.g., fly-by-wire control system.) A malfunction in a safety-relevant system will be a factor in an accident only if that malfunction misleads the operator into making the wrong decision. Safety-critical systems get a lot of attention, safety-relevant systems much less

The anemometer is not safety-critical. It is safety-relevant, whether it’s a factor on not is not known for sure.
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I can relate to this because I once took over a big RO/RO that the ballast tank gauges did not work. The tank transducers have a life of about 10 years. It took me many attempts to convince the company to spend the money to replace the transducers.

The company’s argument was that working gauges were not needed because tank levels can be determined by soundings.

Then the Hoegh Osaka rolled over, I got my transducers. Did the non-working ballast tank gauges cause the Osaka to roll over? Of course not. Were the non-working gauges a factor? Can’t say for sure but I think likely they were a factor.

Ok…I’m an expert at this and I’ve talked about this before. You’ve all got it wrong. You will never run out of gas if you always go with an analog gauge. Or…just pay more attention to it. In short, digital vs analog. I can explain why it in detail and as usual…you can thank me later.


A digital fuel gauge cannot measure the level of fuel in the tank; as soon as it tries to get a reading it changes the fuel level (see Heisenberg).

The same principle can be applied to the gauge itself, if you don’t look at it, it will remain full.

The thing is the digital gauge is “trying” to be accurate, but being a digital thing in an analog world, it has to rely on other cues than actual fuel level to figure out what to display.

It starts by correctly reporting a full tank and figures it can get away with that for a while.

Then, it notices that you keep looking at it and figures that something’s up with that; you, being an analog being must know better than it how much fuel you have left, and that has to be why you keep checking. This causes the gauge to decide that it should turn the top bar off.

By now the poor thing figures it’s done its job and can rest a while, but you keep checking, and the more you check, the more the gauge feels that it should indicate a lower fuel level than the last time you checked.

Of course, the poor thing wouldn’t suffer such anxiety if it were an analog gauge; it could simply move the needle a tiny immeasurable fraction of an amount and feel confident that it did its job.

As it is, the gauge reads the rider more than it reads the fuel tank. I have figured out how its mind works (I knew I was a psych major for a reason…once…but flunked out when I stop taking my meds), and its fun to mess with the digital gauge.

I figured I had done really well when I managed to have it flash low fuel at me only one hour after filling it (I looked at the thing every 2 seconds), but I recently outdid myself: I looked at the gauge so much, that I managed to cause it to indicate empty BEFORE I had even filled it up…

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