# Contact-less liquid level indicator [closed]

I am developing a Liquid level indicator to be used for my lab breaker. The purpose is to get real time liquid level data on computer for analysis.

I have searched for many liquid detectors, but mostly they use ultrasonic sensor on the top of container as shown below, but I want a sensor that could be fixed at the bottom of the container (not in contact with liquid) instead of at the top.

What technique/Principle or type of sensor could be used in this case.

Edit:- I want to know the level of any kind of liquid at any given temperature.

Thanks

## closed as unclear what you're asking by Marcus Müller, Dmitry Grigoryev, Voltage Spike, uint128_t, ThreePhaseEelMar 7 '17 at 0:52

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

• I thought you said water. Of course, the weight will change with the type of liquid. But, the program can be calibrated for different type of liquids . – Umar Mar 6 '17 at 7:51
• Notice that all time-difference based sensors will, just as weight sensors, depend on the physical properties of your liquid. For example, sound travels at different speeds through oil and water, so your Ultrasonic sensor will need to be calibrated for every liquid you use. If you restrict yourself to water, as you said, then things get a lot easier. Are you only measuring water, or are there potentially very different liquids in the container? Why do you want to measure from below? – Marcus Müller Mar 6 '17 at 10:08
• Load cell.? ... – Brian Drummond Mar 6 '17 at 12:54
• @Pierre: yes. It's a problem that people don't ask exact questions on this site. It's annoying that one has ask three more questions back to find out what OPs really mean just because theay are too lazy to imagine that other people can not read their mind. – Curd Mar 6 '17 at 14:11
• Sorry everyone for the confusion so created. I have edited my question. I want to measure level of liquid present in container. By liquid I mean any type of liquid content and at any temperature point. – Ankesh kumar Jaisansaria Mar 6 '17 at 14:25

I guess a pressure sensor and a load sensor do the job.

A differential pressure sensor, with one input measuring the atmospheric pressure and the other one placed at the bottom of the device should measure efficiently the pressure. The pressure can give the height of the fluid as far as it's incompressible one. This height depends on the density, which is unknown (the system have to be liquid-agnostic), but if we know the weight, we may calculate the density depending to the height.

• So we have on one hand:

$$P = P_0 + \rho \cdot g \cdot z$$

With $P$ the pressure at the bottom,

$P_0$ the atmospheric pressure,

$\rho$ the volumetric mass density of the fluid,

$g$ the gravity,

and $z$ the height

• And on the other hand:

$$\rho= \frac{w}{z \cdot \pi R^2}$$

With $w$ the weight,

$R$ the radius of your container, which is considered as a cylinder

We can now calculate $z$.

Edit: I didn't understand if you want to measure always the same liquid (you said you may not measure water), or if you measure different liquids. This answer is for measuring different type of liquids, but if it's not, the load sensor is not useful you can just measure the volumetric mass density of the liquid. If you measure on different conditions of temperatures, it may be considered as different type of liquids, but you can measure the temperature and apply a coefficient of thermal expansion too. Edit2:It's the case so this answer should work