Tank contents gauges

[Graham_Wright]

How do they work?
I thought I understood but, when I came to replace the gauge supplied with the float sender, I realised I don't.
The sender resistance varies between 200Ω and 2kΩ.
A simple ammeter will still register some current at 2kΩ. Calibration can be effected with a resistor in series with the meter but how is the min reading adjusted? Shfting the end stop on the meter would work but is hardly elegant.

 

[Buck Turgidson]

How do they work?
I thought I understood but, when I came to replace the gauge supplied with the float sender, I realised I don't.
The sender resistance varies between 200Ω and 2kΩ.
A simple ammeter will still register some current at 2kΩ. Calibration can be effected with a resistor in series with the meter but how is the min reading adjusted? Shfting the end stop on the meter would work but is hardly elegant.

?
Just write Empty or Full at the minimum reading. No need to shift end stops.

 

[Graham_Wright]

!

 

[penfold]

Generic gauges tend to use the same resistance, the idea being to change the arm length to accommodate different depths of tank.

 

[Buck Turgidson]

Assuming you have the correct probe the gauge is already tuned. If you are making your own then the scale on the gauge just need rotating to align with the needle at zero or if you have a smart gauge you just go through the calibration process.

We need more information to answer your query because the probe is either a linear or rotary potentiometer with standard values at the ends depending on if it's EU or US spec and the gauge is normally chosen to match the probe.

 

[Graham_Wright]

#1 "when I came to replace the gauge supplied with the float sender".
The gauge could not cope with rigours of a sea borne atmosphere and has demised. It looked too "automotive" anyway and will be replaced with rectangular, more cosmetically pleasing milliammeters.

 

[Refueler]

I went through 2 senders before I got anything like a near correct reading.

Despite them having same length arms ... same Ohms rating etc. - they acted differently.

First one would just go to full as soon as tank was 1/3rd full. Tried all sorts of settings / adjustments ... nothing. UK supplied.
Bought same spec but from Chinese eBay ...... once I had sender polarity correct - its good enough ... My tank has rectangular top half and then bottom has a wedged shape - so I would never expect accuracy of content.

 

[Sandy]

I've disconnected my sender as the information it was giving was a work of fiction!

I'm now using estimates of fuel usage and a monthly manual check.

 

[Refueler]

I've disconnected my sender as the information it was giving was a work of fiction!

I'm now using estimates of fuel usage and a monthly manual check.

I still use my dipstick during filling ... two man job ... one man at filler point on deck ... me at tank under stbd fwd bunk. Top access cap open ... dipstick in hand ... fwd hatch open to shout STOP !!

My stick is marked off with 'sawn grooves' and a length of white tape stuck to underside of bunk that lifts out .. the tape is marked off in 10lt marks ....

So I dip tank - hold stick against tape ... instant accurate reading.

For anyone who has difficulty reading a stick - bamboo can be particularly hard ... a stick of chalk .... chalk the stick and the fluid will wash off at the level ...

One day I will create a chart of gauge vs stick ....

 

[Sandy]

I still use my dipstick during filling ... two man job ... one man at filler point on deck ... me at tank under stbd fwd bunk. Top access cap open ... dipstick in hand ... fwd hatch open to shout STOP !!

My stick is marked off with 'sawn grooves' and a length of white tape stuck to underside of bunk that lifts out .. the tape is marked off in 10lt marks ....

So I dip tank - hold stick against tape ... instant accurate reading.

For anyone who has difficulty reading a stick - bamboo can be particularly hard ... a stick of chalk .... chalk the stick and the fluid will wash off at the level ...

One day I will create a chart of gauge vs stick ....

I did that in my old boat, but the current one has a filling pipe that is an S bend. At the bottom of the S Bend is a 'shaped tank' that fits neatly into the transom and is easy to remove; a superb bit of engineering. The downside is I cannot poke a stick down the filler and dip the tank to check its level.

Over the last few years I have been carefully recording my fuel usage and now have a good average lts/hr figure. Over the winter the tank was removed, emptied and cleaned. I know the exactly the amount of fuel that refilled the tank and it is now simple arithmetic with a monthly double check - remove a panel and filling hose then checking that the fuel level is near the top of the tank.

 

[Refueler]

My tank is an ex truck tank and has a screw based access cap - giving direct dip point. The filler pipe has bends and so on - so no way via that - but no need anyway.

 

[geem]

My diesel tank and my water tank are grp and built in to the boat. Both are sat above the keel. The tanks are wine glass shape as a result of the tanks being in the upper part of the keel and above. No sender unit would give a true reading. Thr boat used to have them but really only told you full and empty with nothing in between. Since the water tank is 800 litres and the full is 500 litres, it wasn't helpful. Both now have their own dip sticks. Super accurate.
I purchased a couple of 1" bronze fittings with screw on caps that I fitted to the tank access lids. The dip stick simply pokes down the hole for a true reading

 

[vyv_cox]

I replaced my old float and lever sender with an Osculati column type. Tank fitting is identical and accuracy considerably improved.

 

[webcraft]

The gauge on on Avy-J runs backwards - full when empty, empty when full. OK once you get used to it. I reversed the wires from the sender but it made no difference.

- W

 

[NorthUp]

Two interconnected tanks at different heights and capacities were going to be complicated to measure- instead I fitted a domestic water meter at the pump outlet to measure how much I've used. Tank capacity is known, and I fill to full every time. A remote counter makes it easy to read, and one day I'll find a cheap counter able to count down from full .
It's accurate to better than a litre.

 

[geem]

Two interconnected tanks at different heights and capacities were going to be complicated to measure- instead I fitted a domestic water meter at the pump outlet to measure how much I've used. Tank capacity is known, and I fill to full every time. A remote counter makes it easy to read, and one day I'll find a cheap counter able to count down from full .
It's accurate to better than a litre.

I do the same on my water tank. I have details of a pulse counter that I use. Accurate to 1 litre if you need it? My problem is that we fill the water tank from the watermaker so we don't keep the tank full.

 

[QBhoy]

How do they work?
I thought I understood but, when I came to replace the gauge supplied with the float sender, I realised I don't.
The sender resistance varies between 200Ω and 2kΩ.
A simple ammeter will still register some current at 2kΩ. Calibration can be effected with a resistor in series with the meter but how is the min reading adjusted? Shfting the end stop on the meter would work but is hardly elegant.

The range min limit and max limit figures you’re getting there, aren’t right. European senders will have a range of about almost 0-180/190ohms or close. Senders of us origin are almost the complete opposite way around. 230ohms to very little. 20 or 30 ohms maybe.
Not sure what’s going on with yours there.

 

[lustyd]

The gauge on on Avy-J runs backwards - full when empty, empty when full. OK once you get used to it. I reversed the wires from the sender but it made no difference.

- W

US and EU senders work in different directions, with high resistance at the bottom or top of tank. it's a resistor so swapping wires won't help. Electronic gauges are able to change between the settings.

European vs American Resistance

I assume this is because EU tanks are more likely to be empty while US tanks more likely to be full based on traditional fuel prices, and in theory lower resistance will use less power.

 

[Graham_Wright]

When filling the tanks with two bodies available, one goes below to watch through the tank access cover and the other drives the filler nozzle. Due to foaming, it is necessary to periodically wait for the bubbles to disperse. When filling single handed, there is a real danger of overfilling (proved).
I do have a "full" warning sensor (by Honeywell, I think) but it has never been commissioned. Perhaps it needs to be moved up the list.
I have three tanks that need level sensing. The water tanks are all Plastimo flexible individually valved, easy to monitor and not gauged.

There are two top-of-bilge-keel tanks for fuel and a black water tank in the fore cabin. The latter has a cylindrical sensor with an internal float and a set of reed switches. I don't believe a lever arm switch would cope too well in black water!
I will recheck the resistance readings and there was some evidence of dirty contact with the sweeper arm. I am reluctant to change the fitting as swarf in the tank would not be a good idea.
As an addendum; a word of warning to others. If you leave the gauge out and do not then seal the opening remaining, do not go ashore using a hoist that tilts. (Don't ask!).

 

[rogerthebodger]

I fitted a float switch in the top of my fuel tanks.

These float switches are connected to an LED and buzzer so when the tank is almost full the LED illuminates and the buzzer sounds.

I have a dip stick the I marked at 20 lit increments while I was first filling the tank from 20 lit cans.

I also have a capacitor type of tank sensor that has an output of 4 to 20 mA with a 4 -20mA gauge from VDO. these can be cut and set to zero and full to compensate for various lengths of sensor

These sensor came for US and can be connected to an intelligent gauge that can be programmed for all shapes of tank to give correct fuel contents.

I got these some 15 to 20 tears ago