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Water Meter

  • Fyko van der Molen
    Fyko van der Molen on

    Both the 0 – 1000Kg and the 0 – 2000Kg load cells we supply are classified C3, which means accuracy of better then 0,023% across the entire range, from 0Kg to max.

    You should be aware that a shear beam load cell is effectively a lever. For best accuracy the load should be centred on the load button – further out it will measure more, closer in it will measure less. The circular DYLF-102 also wants the load centred to keep the strain equal all around the perimeter.

    The load button is often the head if a 12mm (19mm AF) bolt with non-slip grooves ground in to it. Try to keep the load distributed equally across the width of the bolt head.

    Fyko van der Molen
    Fyko van der Molen on

    The WeighStar mass meter shown in previous posts can now accept, and be switched between, a variety of pre-programmed load cells.

    So you can unplug the jack-top unit that you weigh your truck axle with and plug in the baby that measures you gas bottles or jockey wheel.

    As new load cells become generally used we add them to the pre-programmed list.

    Josef Konrad
    Josef Konrad on

    Is there a best way to mount the flow sensor? Or will any orientation work equally well?

    Fyko van der Molen
    Fyko van der Molen on

    A flow sensor will work in any orientation – it will even work when connected to it’s hoses back to front.

    But there’s a difference between ‘working’, ‘working better’, and ‘working best’.

    Some people are not too concerned about pin-point accuracy. I’m told they even buy a garden-hose attachment, insert it into the plumbing, and then climb under their caravan to read a device that gives them a flow count that’s between 80% and 90% accurate, at best.

    We value consistency above accuracy. If we have a flow sensor that is 96% accurate we can make that into 100% accurate with a user input that takes seconds to complete. If the sensor is then consistent to within 1% then we have a perfectly accurate device. That is to say when the 100 litre tank runs out the water meter says 100 litres – not 99 and not 101.

    To get good consistency you need the best orientation of the sensor. For bucket-wheel sensors that means a horizontal water flow axis with the bucket-wheel chamber hanging downwards. A bucket-wheel upwards orientation will have the wheel chamber filled with air, and that air remains trapped for ever after. For some reason that trapped air subtly affects the consistency of the sensors output – only by a percent or 2, but that’s significant if perfection is your goal.

    Similarly, bucket-wheel chamber to either side affects the repeatability of the sensor by a few percent, possibly due to the tiny amount of friction that arises from the  rotor touching the internal body where the shaft enters the side wall.

    So, horizontal water axis, with wheel chamber down is the ‘works best’ orientation.

    As I’ve mentioned before some serious adventurers add a high-capacity sensor into there filler pipe so that partial replenishment from rain water runoff can be factored into the total water resource remaining in the tank. This sensor generally cannot be mounted horizontally because the direction of the pipe is downward and there’s no room for the insertion of elbows.

    This, coupled to the fact that air bubbles present in the incoming flow will be interpreted as water, presents a challenge. Fortunately the sensor we use on the inlet pipe works pretty well in the vertical orientation, and we have a few tricks to remove the air bubbles before they pass through the  sensor, so we can still achieve an accuracy of better than 98% on measuring the inflow.

    Simon Tasman
    Simon Tasman on

    I use a brass YF-B6 inserted into the inlet pipe and an S201 on the outlet

    When I add water I keep the inflow going as fast as it can without spilling.

    The outflow has the standard s201 mounted for horizontal flow with the bulge downward.  I’ve found that +8% is exactly the right compensation factor.

    With this setup I get accuracy of better than 99%. I would claim 100% but I  know nobody will believe me, so I downgrade to 99%.

    Fyko van der Molen
    Fyko van der Molen on

    There’s a certain amount of luck involved in getting the inflow to exactly match the outflow.

    That’s because the clocking rate (the number of electronic clicks per litre passed) is not the same between differing sensor types. To avoid resource-sapping arithmetic in the MCU we take 1/10th litre bites out of the outflow whenever 1/10th litre is detected in the inflow.

    If the last of the inflow fails to make the last 1/10th litre cut then that quantity will not be deducted from the outflow. Therefore on any replenishment, whether it be of 10 litres or 50 litres, it is possible that the last 1/10th of a litre does not get counted.

    You wouldn’t normally notice this but if you do then that’s the reason. We prefer any errors to be on the conservative side so that when the meter reads zero there’s still a life-saving litre in the tank, rather than the other way around.

    The brass-bodied B6 is one of the best flow sensors available, when it’s available, which is not always. They’re also the most expensive and hence not very popular.

    Joe Steele
    Joe Steele on

    The yacht people should know about this product.

    Every drop of freshwater used on a sailboat must either be manufactured by desalination carried aboard from the shore.

    As a charter skipper there’s been many occasions that I’ve had to gently rebuke a guest for wasting precious water in the shower. Amongst the islands winds are often light and the only viable energy source being the sun is insufficient to keep the tanks replenished.  A buzzer after 3 litres would have been moet helpful.

    As it was I’d listen to the pump running endlessly, gnashing my teeth, waiting for it to end. I should have had one of these devices, with the buzzer right there in the boat’s head next to the guest’s ear.

    Fyko van der Molen
    Fyko van der Molen on

    We do get the odd inquiry from a yachtsman, but for every boat owner there’s a hundred caravanners. From my own time operating a 40′ catamaran between Bazaruto and Comoros I know that the waterhog alarm is the most desirable thing to have. Yachts tend to have water tanks located opportunistically, feeding the lowest located in the keels, from which at least 2 pumps selectively supply the heads and the galley. A complex system to manage but yes, the common problem is the waterhog, and the buzzer is totally impartial. Nobody feels picked-on because it’s a machine doing the griping.

    I had a rainfall capture system on the bimini with lots of drains feeding the nearest tank inlet. The flow rate from captured rainfall would be too low for reliable metering so the only practical way to determine water resource was to dip the tanks. Some thing that’s not available to the caravanner when the tank is under the floor.

    Amongst caravanners it’s generally the one that fills the tanks (Dad?) that wants the alerts for wastage and low tank-level. The less-than-20% alert serves to notify that replenishment will soon be needed.

    For us the challenge is that bubbles contained in the replenishment water will be read as water, thereby giving an optimistic reading. The answer is to keep up a fast and steady flow that keeps the inlet tract filled to near the neck (without allowing overflow).

    Without air bubbles passing through the sensor the accuracy is near perfect, but we nevertheless keep any potential error on the conservative side, so you may have a litre or 2 more than you think you do.

    Joe Mattisson
    Joe Mattisson on

    I’m planning to move to smaller, lighter SUV in the near future. I haven’t made a final decision yet, but I’m seriously looking around.

    What I see happening is that the weight factor of the trailer is going to be a lot more important than before. If the gross of the trailer must be less than the Tare of the car then I need to know the actual of both. I want to weigh the car and I want to weigh the trailer. Not just once, but every time.

    Several posts back there’s some info about a home-based weighing device. I need something that will tell me the actual weight of my car, the actual weight of the trailer in toto, and the weight on the towball.

    Please supply more info.



    Fyko van der Molen
    Fyko van der Molen on

    Hi Joe,

    This is a question that arises increasingly as people downscale to smaller vehicles, and I think it deserves its own thread.

    I’m going to copy your question and transfer it to the top of the new thread where I’ll elaborate a bit further.

    Fyko van der Molen
    Fyko van der Molen on

    We now make this device in an all-white enclosure:

    Dan Perkins
    Dan Perkins on

    I was wondering why I was getting such a big reading error  – about 30% under reading. Then I put on my glasses and saw the little arrow I’ve heard about but never saw before.

    I turned the sensor so the water flows in the direction of the arrow.

    Hey presto! Now it’s 99% accurate.

    I blame the fact that I installed it after work when it was already nearly dark – in a hurry as usual.

    Be sure to identify the arrow and don’t make my mistake.

    Dan Perkins
    Dan Perkins on

    I have a 105L tank in my trailer, according to the specs. My pump delivers 10 litres per minute.

    Today I filled the tank and pumped it dry. When the last litre went out the meter read 106 litres.

    I’d say that was pretty accurate.


    Fyko van der Molen
    Fyko van der Molen on

    We’ve now added a hi-resolution electronic voltmeter to WaterWatch:

    The battery voltage is continuously monitored at the point of entry. If the WaterAlarm buzzer is fitted then a buzzer alarm will sound when the battery voltage becomes critically low (11,4V).

    Excessive discharging is still the leading cause of premature battery failure.

    Fyko van der Molen
    Fyko van der Molen on

    We have now reached a level of accuracy that allows measurement to 2 decimals of a litre.

    You might not need this level of precision when you have a shower, it it’s a big help when you’re cooking and you need an exact quantity of water.

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