Accurate Yet Economical Gasoline (Petrol) Flow Meter

1. Your arithmetic is off. 997 to 1003 is a 0.3% (not 0.03%) margin.

2. Suppose you do find or create an accurate meter. You go to a filling station that says 1100 mL, but your meter says 900 mL. How are you going to win any argument over that?

3. A flowmeter, strictly speaking, gives instantaneous flow rate, which would then need to be integrated over time to give total volume.

Hi Tornado,

1. You are right. It is 0.3%.

2. The idea is to identify good gas stations and stay away from flawed ones, not fight with the flawed ones. (Not interested in getting beaten by Petrol station owners )

3. So, I tried a prototype with Hall Effect Flow sensor, Adruino Nano and a monochromatic display. So, at home, I would use a motor to pump constant pressured water into the sensor. The sensor sends the data to Adruino and then to the display. I am getting 3% error margin (970-1030 ml) as against the need of .3% (997ml - 1003 ml). Also, the sensor is big for fitting in a motorbike. This is where I need help. A small sized, highly accurate flow sensor is my need.

I am thinking of forming a network in my city, by giving it to my friends so that I would know the best Petrol stations in the city. This data can be shared through a website/app/etc. This is why it should be automotive grade so that I can confidently give to people.

What do you hope to gain by doing this?

An 0.03% reduction in operating costs, perhaps (rhetorical question - NNTR)? Life is too short as it is....

Petrol theft at petrol stations is a huge issue in India. So, if this works, then I could sell this product to all motobike owners and create a map of accurate petrol pumps.

What is the payoff for CR4 contributors to this design, then?

Why do you need to measure the "flow rate"? Surely it would be simpler just to measure the total volume of petrol delivered and compare with the station meter.

Calibrating a dipstick for a motorcycle gas tank is a bit laborious, especially as it depends on the tank being tilted the same way every time.

Don't you just need to fill a 5 litre jerry can?

How would I know the total volume of petrol delivered? Right now, the only possibility is to check the station meter. Every customer has a right to request Petrol station owners (in India) like the Filter paper test for quality, 5 litre can test for quality. While Government has mandated these at the petrol pumps, customers are often assaulted for requesting such tests. Most Indians won't even dare to ask that question. So, my idea will ensure people don't go to such petrol stations.

Problem 1): <...The petrol pump has an error margin of .03% ... receive 997 ml - 1003 ml...> Those two numbers are inconsistent. An error of <...[0].03%...> would give 999.7 - 1000.3ml. <...error margin is 5% 10 times more...> 5% divided by 0.03% gives a factor of 167, actually. So the first step is to sort out the numbers.

Problem 2): There has been no mention of temperature. Volume varies with temperature, and therefore the fuel's calorific value per unit volume will vary also with temperature.

Problem 3): If two meters are in use on the same stream, which one is right (rhetorical question - NNTR)? The vendor will claim that the only meter that can be used for charging is the fixed installation, leading to a forecourt argument and, as a minimum response in a range of possibilities, an invitation to take one's business elsewhere next time.

• If this level of detail is involved in trimming the economics of vehicle operation then maybe it is time to consider other actions, such as replacing it with a smaller one, or selling it and using a pedal cycle or walking instead.

@PWSlack -

1. About Error margin - My original post has this error. The error margin is .3% - 997-1003 ml per litre.

2. About Temperature - You are right. With change in temperature, the density changes (in a big way for Petrol); however gas stations are expected to maintain a particular temperature at their storage tanks. Actually Temperature test is one of the quality tests; if the temperature is not same as promised, then it means petrol has impurities.

3. About argument with Pump owners who's right: So the basic idea is to stay away from corrupted petrol stations; not cross-check and pick an argument; In India, Petrol pump owners are stronger in every way and only very very few consumers will ever dare to pick a fight with them on quality. If you have an Indian friend, they will tell you stories.. :-)

Thanks for your comment. The original question remains. Will you help me find the right kind of fuel sensor that would be appropriate for measuring petrol?

Invitation declined. There is no mention of a fee for contributors to this design, and yet the declared intent above is to design and sell a product. Get real.

@ Rixter: You just need a graduated cylinder. I don't know about the accuracy you desire.

1000 ml graduated cylinder

Most petrol stations in India will not entertain using a graduated cylinder. In fact there is a government rule in some states that forbids filling stations from filling fuel in bottles/graduated cylinders, etc. Also, as a pump owner, if I know that I am only filling 950 ml per 1 litre of petrol, I would I let my customers measure? That's why we need a way to measure petrol, without asking questions and not relying on the pump reading.

So, basically I need a fuel sensor that can accurately measure fuel as it flows into the petrol tank at petrol stations.

So, you are going to spend hundreds of $s to save...how much on inaccurate gasoline pumps?

There are no economies to be gained here. Rixter is correct, get an accurate lab graduated cylinder, and use it to calibrate a gasoline container. Very cheap and easy.

Otherwise, you are going to be trying to compete with the petrol station's meter by making your own "lab accurate" totalizing flow meter......to save what?.....pennies on the dollar? You could use all that cash to buy petrol......!

Calibrate a petrol container.....use it to find an accurate petrol bunker.

.....and if not, get a 12v metering pump to pull petrol from your non-calibrated container......many of them have totalizing displays on them. Pretty dangerous handling gasoline this way......and downright expensive......but you will have your toy so you can argue with the petrol stations.

So when you "discover" this scam...don't go there any more!

Pennywise and pound foolish.

Your best bet is to purchase your petrol when the storage tank, and the petrol inside, is the coolest.

Otherwise, you are wasting your money and time.

As mentioned before, this is a real problem in India (and other nations where government is not very enforcing).

Lets take a real example... I need 50 litres (13 gallons) of petrol per month (conservative number). At INR 64.24/litre (almost a $) that costs me INR 3212 (~USD 50). If I get cheated at an average rate of 50 ml per litre then I stand to lose 2.5 litres per month INR 160 per month or ~ INR 2000 per year ($30 per year).

Bottom line is I don't lose $30 per year. I am consistently getting cheated all round the year.

And 50 ml per litre is a very conservative estimate.

So my question is, Do you know of a fuel flow sensor that would a good starting point for me to research and build this product?

Looking for a engineering solution not a workaround like using a measuring jar. Most of us already know a petrol pump that is less corrupt; I want to make quantity & quality an objective discussion (Eg: Petrol pump A has a 99.3% accuracy as compared to Pump B which is only 95% accurate) instead of a subjective discussion (Eg: From my experience, I think Petrol pump A is accurate ).

Looking for engineering recommendation like,

1. Magnetic flow meter will not work for this scenario as it works based on liquid conductivity.

2. Ultrasonic sensor might work.

3. "____" sensors is ideal for this scenario. They are also much accurate...

Thanks again for the overwhelming response so far! This is my first post in this forum, and I can't believe so many people want to help! Thanks.

Re 1., I was about to point that out in response to your #2.

That's a good idea.

However I want the solution to be as non-intrusive as possible; something that is DIY or plug & play kind so that I don't need a mechanic to fit it to each vehicle.. With Load cell, I need to know the weight of each fuel tank and calibrate accordingly.

The difficult part is ensuring a load cell support design the captures most of the mass. The strain gauges have a pretty good range, and they are linear, so you just need to know the volume of fuel convert it to weight, and allow a few kg for the tank. If each of perhaps 3 cells was rated for the total load, that would give you good accuracy & repeatability.

These devices are small, and can be integrated into the fastenings for the rubber bumpers that support your fuel tank.

Once it is calibrated, with a known volume of fuel, perhaps an average of different fuels, then you will be able to measure the performance of your other pumps. You can just do it as percent of your standard, don't even need to know actual grams.

I don't think this solution is something you can install economically on many consumer vehicles, but you might be able to make a living at burning petrol & reporting on a subscribed blog the results of your research. Keeping a low profile, of course.

However, if you partnered with a local manufacturer of motor bikes, the cost of an engineered solution mass produced could be far less than the perceived value to your customer, and it may help their marketing and sales volume until others caught up, or until the oversight at the pump improves

Could you put load sensors on the tank mount and weigh the tank?

Are there no authorities in your local area to carry out periodic tests at the pumps? We luckily have such folks here.

There are authorities, a system and periodic tests do happen; however there is also pumps that still get away with it. The Petrol industry in India is government regulated (controlled) which I feel is the source of the trouble as it leaves little scope for private players to compete.

Each pump could conceivably be over or under on any given day with such little oversight. Even rhe honest dealers wouldn't sweat such a small fluctuation

Considering all of the laxities you have mentioned, do you even know the quality of the petrol that is being pumped?

Just like the saying "There's more than one way to skin a cat", there's more than one way to scam a customer.