Project: Different types of liquid level indicators

This project is all about the different water/fluid/liquid level indicators for water tanks at home or any place where it is required to measure the liquid level. This project describes three different types of water level indicators and also gives details on how to implement them.

Importance/Aim of liquid level indication

We know that nowadays instrumentation plays a vital role. Process industries often require liquid level indication for controlling different parameters. One can take the example of the domestic water tank in which we need to know the level of water so that we can determine the time at which we should start the water pump and so on.

I have conceptualized three different types of liquid level indicators which I want to share with you and this will surely help other engineering students how to think creatively for projects and any task. This is 100% implementable. You can try to implement it at your home.

Description about each liquid level indicator

There are three types of water level indicators given here.

1. Transparent glass tube level indicator
2. Dial indicator
3. Digital indicator

Different liquid level indicators

Transparent glass tube level indicator

This is a type of analog or manual liquid level indicator. As shown in the figure-1, the Transparent Glass tube indicates the same level of water/fluid that is in a water tank. When water is filled in the water tank, water also flows to the glass tube along with the tank and the level in the tube is the same as that of the tank. This is due to the fact that when two open vessels connected at the bottom are filled with water/liquid, the level in both the vessel is same due to equal pressure (atmosphere pressure) from both the vessel. (as shown in Figure-2)

Governing equation is Pressure = Density x Gravitation acceleration x liquid level or height. So, the liquid level is directly proportional to applied pressure. In this case, atmospheric pressure is equal for both water tank level and glass tube level, so, the height of the water is the same in both.

manual liquid level indicator

NOTE: These project images are drawn in the MS Paint program.

Dial indicator

This indicator works by rotation of gears in sequence when the float in the water tank, changes the position during different water levels. This is due to the fact that float is lighter in density (due to lighter in mass, When we take water equal to the volume of float, it is higher than air-filled in float ) compared to water density. So, when water is filled inside the water tank, the float goes upward by floating.

As the float changes its position due to a change in water level, a gear-1, connected with float connecting rod, rotates and indicator (gear-3) shows level on a circular scale as high, low, medium, or intermediates.

Digital indication

When gear-1 rotates due to change in position of float corresponding to water level, rake/rack connected with gear-2 reciprocates. The slider connected with rake slides over Rheostat. The change in position of the slide(corresponding to liquid level due to change in position of float), causes a change in resistance (Due to change in connected length of wire because resistance depends on the length of wire, Resistance is proportional to the ratio of length and diameter) of wire connected with Rheostat. This information about the change in resistance goes to the controller which shows a digital display about water level position.

If the water level falls below the very low-level point, the controller sends a start signal to the motor which eventually starts the water pump. When the water level reaches a high level, the controller shuts down the motor and hence water pump stops.

This is my genuine project idea. It does not contain any part which is extracted from anywhere else. This project is implementable.

Material Requirement for liquid level indicator project

  • One transparent glass tube with its length equal to total height of water tank.

  • One hollow spherical float, you can use plastic ball used for children cricket play.

  • Three different gears, according to the project requirements.

  • Controller, PLC

  • Dial indicator

  • Rake with same gear profile matching with 3 gears.

  • Rheostat to change resistance

  • Note: The location of each part depends on the project condition and as per requirement. You can build a wooden platform on which every part can rest for support.


    As far as the cost of the entire project is concern it contains costs related to all three types of indicators.

  • Transparent Glass tube Indicator: Cost around Rs. 100-200 with scaling and purchasing of the tube. This depends on the price of the glass tube and the height of the glass tube based on the height of the water tank.

  • Dial Indicator: Simple toy gears are available in the market. You can calibrate the dial indicator based on one's water tank by emptying, filling and at midway levels.

  • Digital Indicator: The cost of gears and rake are depended on which size of the gear and rake you are using based on the displacement and other issues. Rheostat and controller can be available in the market based on the resistance change and type of controller you want. Motor and water pump can be easily available at home.

  • Academic/Practical importance

    This project helps at the domestic level by reducing water wastage during the high levels of the water tanks. It automatically switches off the motor of the water pump.
    Sometimes water tanks are inaccessible/under-water tanks then, liquid level indicator helps you to find out the correct level.

    This project can also be taken as an academic project ensuring proper design.


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    Guest Author: muhammad abdul quyyu01 Oct 2014

    please anyone tell me a mini project related mechanical engineering of subject theory of machine

    Guest Author: muhammad abdul quyyu01 Oct 2014

    good one. Nice reading this

    Guest Author: veerakumar11 Oct 2014

    Nice to see this article

    Author: Umesh07 Feb 2018 Member Level: Platinum   Points : 8

    A very good model for understanding the pressure of liquids in different sized vertical containers as well as to use the changing level of liquid to move a floater to know the water situation in the tank.

    The article has generated a lot of ideas and for small children, I will suggest that they can make a model on similar lines to show how we can use the moving water level to other useful information.

    For example they can fill water in a small can with a water tap in the bottom to discharge the water out and use a float ball in it which is fixed to a string going through an ordinary wooden pulley or bobbin and another end of string can be attached to another bobbin and wounded over it a few turns. On the second bobbin one can attach a needle which moves on a fixed circular cardboard. These things can be fixed on another thick cardboard stand or wooden stand.

    Now when you drain the water out of the can the float will move down and the second bobbin will give out some string and needle attached to it will also move.

    So one can calibrate this needle from full to empty position and it is a good indicator to know the level of water in the can at any time.

    Similarly, there can be many other ideas which can be generated after reading this article and students can make working models.

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