Capacitive Liquid Level Sensing (1): Sensor Basics

[@PM12951]

Thank you Professor for this excellent explanation of capacitive sensors. I enjoyed this toughly!

[@robertssmorgasbord]

You're welcome! I'm always happy if my videos are useful to somebody. BTW I'm not a Professor 😅

[@favouremmanuel8876]

Thank you very much for this Sir, I was building a cylinderical capacitor for diesel level sensing and this gave me more clarity

[@robertssmorgasbord]

You're very welcome! I'm always happy when my videos are helpful to somebody. Don't forget to watch the whole series. Especially the last part were I correct a fundamental error I made and measure some vegetable oil (didn't want to handle diesel) levels.

[@Solarlehrling]

Hallo Robert Vielen Dank für den interessanten Beitrag. Bin schon sehr auf das nachfolge Video gespannt.

[@robertssmorgasbord]

Immer gerne! Das nächste Video (03.09.) wird etwas unstrukturiert. Mein Brymen Multimeter hat nicht das gemacht, was ich erwartet habe, und mir fehlte ein IC. Aber ab dem 10.09. sollte es hoffentlich etwas besser weiter.

[@ZmankoAhmad-nx4hm]

Hi professor, Hope you are well. I do really enjoy your well organised video regarding the capacitive topic. I have set up a capacitive water level sensor system with a micro processor for the display and another one for the probe on the tank. The length of the three wire connection between the display and the probe (sensor) is directly affecting the readings and also I get interference between the cable and any metal, floor ground, touching the wire …etc. The question is how to buffer the system from interference and also how to make system adapt to any length of wire between the probe and display? Your insight will be much appreciated.

[@robertssmorgasbord]

Well, first of all I'm not a professor 😅 Anyway, following along this series you'll see that keeping the wires short is the key to success. Ideally your measurement electronics are directly connected, respectively, as close as possible to the sensor. After you converted the capacity of the sensor to something digital (or something more robust analog, like 0V to 5V), you can transmit the data over a distance. Connecting the sensor over any lenght of wire to the electronics is not advisable.

[@Sh4dowHunter42]

Robert, you have a wonderful mind which is complimented by an elegant and succinct tongue!

[@robertssmorgasbord]

Thanks for the praise! You really got me blushing here 😅 And of course you're very welcome!

[@nmjerry]

Really good video.

[@robertssmorgasbord]

Thanks for the praise! And you're welcome!

[@rene-jeanmercier6517]

Hi Robert. Only you can have such an idea to do that kind of experimentation !!! I loved it ! RJM

[@robertssmorgasbord]

Hi René-Jean, I'm just standing on the shoulder of giants and fooling around a bit. Also, I'm trying to avoid differential and integral calculus in my videos 😅 But I'm happy you liked it. Regards Robert

[@ignist2840]

Dear Professor, At 07:06 I am confused about the definition of the relative permitivity. If only the medium in BETWEEN the plates changes the relative permitivity and not by medium OUTSIDE of the plates, then how would the total Capacity change if a tank is filled with liquid SURROUNDING the capacitive sensor? As the liquid doesn't reach in between the plates, all variables relative permitivity, area and distance stay the same. Thank you for these videos. They are really helpful.

[@robertssmorgasbord]

Have a look at kzbin.info/www/bejne/gJvGqqBonJelq80si=SiwEn3d_g7vvwXCx&t=530 : The permittivity of the medium between the plates (parallel field lines) is indeed constant, because the medium doesn't change there. However, there are also field lines on the outside of the plates (curved field lines), and those cross through the medium we're measuring (air vs. liquid). Thus the relative permittivity of the medium these field lines cross is changing. Hope that helps. BTW I'm not a professor 😅

[@ignist2840]

@@robertssmorgasbord Thank you for your time to answer me! It is clear now. Sorry for the professor mistake, the other comments threw me off guard haha. Keep up the great work.

[@robertssmorgasbord]

@@ignist2840 No problem! And you're very welcome!

[@ignist2840]

@@robertssmorgasbord Dear Mr. Smorgasbord. In our project we are struggling with our capacitive sensor with regard to measuring the liquid level in a sewage tank. After a day, the full and empty signal are not correct anymore. Is there a possibility to discuss this issue with you or do you know other experts in the field of capacity sensors that we could contact? The troubleshooting discussion with our supplier did not lead to a solution.

[@robertssmorgasbord]

@@ignist2840 I'm sorry, but KZbin is just a hobby for me and my real-life profession leaves me very little time spare time. So I'm not really able to lend you a hand here. I also don't know nobody else who could help you. That said ... The problem of measuring the level in sewage tanks (in marine application called grey and blackwater tanks) is that you might have particulate matter in your liquid that might stick to your sensor and thus throw the readings off. One counter measurement is a non-stick coating (e.g. Teflon) on the sensor. Another solution is to use a different kind of sensor. Here pressure sensors come to my mind (e.g. www.sensorsone.com/hydrostatic-liquid-level-sensors/ ).

[@faridfarrokhnia1890]

grate video,also please do try it with the chip as well should be interesting.

[@robertssmorgasbord]

Thanks 🙂Do you have a certain preference regarding the chip? I could go with the TI FDC1004 (0.5 mm pitch VSSOP package - pain in the behind) or the Analog AD7745/AD7746 (0.65 mm pitch TSSOP package). But it will take some time to source those chips.

[@baderabdalwali6828]

Hello sir , I have a question please. How can I maintain the error of measuring equal to 1 if I change the parameters like the distance between wires, electrodes or even the radius of the wire?

[@robertssmorgasbord]

If you sensor geometry changes along the length of the sensor in any way, you'll have to compensate for that in software. That is you have to take calibration measurements for as many fill levels as possible, store those value pairs (capacitance, fill level) as a table in your software, and then calculate the fill level from that table and your capacitance measurements (apply linear interpolation between data points of your table).

[@ZmankoAhmad-nx4hm]

Hi master, very well explained and I enjoyed it a lot. What about if the two capacitive plates ( let’s say two stainless steel rods ) housed in PVC pipes each and separated for the distance of 1cm? Do you think this works to use it as the water level reading in the tank? Thank you

[@robertssmorgasbord]

Hi, yes, that would definitely work. However, you will have a smaller capacitance / smaller capacitance changes.