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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. Existing technique available

Required a sensor that could be attached at bottom of jar

Thanks

Ankesh kumar Jaisansaria
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  • If it is the level you are concerned, then a weight sensor can do. Why not UV by the way? – User323693 Mar 06 '17 at 07:42
  • If we use weight sensor then will the type of fluid/liquid inside breaker not affect the readings? – Ankesh kumar Jaisansaria Mar 06 '17 at 07:49
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    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 . – User323693 Mar 06 '17 at 07:51
  • Can UV be used,as the sensor has to be at the bottom of container? – Ankesh kumar Jaisansaria Mar 06 '17 at 07:53
  • if you meant, UV intensity sensor, i am not sure. I think it may need constant light source so that only the effect of liquid should be sensed by the UV sensor. Outdoor light may also be monitored for cancelling the defect, But, i am not sure. I will leave that to experts – User323693 Mar 06 '17 at 08:12
  • Look for ultrasonic sensors. –  Mar 06 '17 at 08:21
  • @GregoryKornblum Will Ultrasonic sensor work below container? – Ankesh kumar Jaisansaria Mar 06 '17 at 08:29
  • If you choose the right one, of course –  Mar 06 '17 at 08:40
  • You might also be able to use piezoelectric sensor to detect the sonar reflection from the surface. (Pulse the sensor and time the reflection.) – skvery Mar 06 '17 at 09:44
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    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 06 '17 at 10:08
  • @Ankesh kumar Jaisansaria: See similar or duplicate question http://electronics.stackexchange.com/questions/190000/water-level-sensor-circuit/190016#190016 – Curd Mar 06 '17 at 13:19
  • It's not, because this one seems to be for all liquids, and the other is for water only. – Pierre Mar 06 '17 at 13:21
  • @Pierre: OP here mentions "water" as liquid whose level is to be measured and BTW measuring methods in other answers work for non-water liquids too. So it's very well a duplicate question. – Curd Mar 06 '17 at 13:49
  • Main reason for me asking this as a separate question is because I specifically require the sensor to be placed at the bottom of the container. – Ankesh kumar Jaisansaria Mar 06 '17 at 13:59
  • @Curd you're right, he mentions "water" (but he precise liquid), and other solutions work for non-water liquids too... But it seems that he want to measure differents liquids not always the same. In fact it's still unclear. – Pierre Mar 06 '17 at 14:06
  • @AnkeshkumarJaisansaria please, can you answer? do you want to measure different types of liquid or in different temperature conditions? – Pierre Mar 06 '17 at 14:08
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    @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 06 '17 at 14:11
  • @Curd I could not have said it better, you read well in my mind, we see you're trained at – Pierre Mar 06 '17 at 14:12
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    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 06 '17 at 14:25
  • do you need accurate level on the full range or just at certain thresholds? – ratchet freak Mar 06 '17 at 12:20
  • Accurate level on full range – Ankesh kumar Jaisansaria Mar 06 '17 at 12:21
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    Load cell.? ... –  Mar 06 '17 at 12:54
  • http://engineering.stackexchange.com/q/3868/33 – hazzey Mar 06 '17 at 14:40
  • One _possible_ solution I can think of is using an infrared sensor. Probably requires some knowledge of radiometry, however. –  Mar 06 '17 at 14:41
  • How accurate? How expensive? etc. – Carl Witthoft Mar 06 '17 at 16:08
  • Good level of accuracy at lowest possible price – Ankesh kumar Jaisansaria Mar 06 '17 at 16:20
  • You could try an optical time-of-flight sensor - see https://www.adafruit.com/product/3316 for example. It would depend on the reflection of the liquid/air boundary. – tomnexus Mar 06 '17 at 20:54

1 Answers1

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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

Pierre
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