Capacitive Liquid Level Sensing (1): Sensor Basics

First part, covering capacitance and general sensors design …
↓↓↓ Complete description, time index and links below ↓↓↓
Capacitive liquid level sensors are neat: They have no moving parts, there is no current flowing through the liquid you measure, and the capacitive sensors themselves are fairly easy to build. But of course they come with their own challenges.
We first have a look at the theory of capacitance, in order to understand what influences the capacity of a capacitive liquid level sensor. Then we proceed to do some experiments with different basic capacitive liquid level sensor designs.
00:00 Intro - capacitive liquid level sensing
00:11 Capacitors - what influences the capacity
02:41 Capacitance - the theory without math
14:51 Demo - of parallel plate capacitor
16:31 Experiment 1 - plates close together
19:49 Experiment 2 - plates with cavity in between
22:49 Experiment 3 - plates at distance without cavity
24:39 Experiment 4 - plates outside liquid container
29:28 Experiment 5 - metal container with plate inside
31:50 Wrap-up - next is measuring the capacity, bye
Tutorials • Tutorials
#liquid #sensor #capacitance #capacity #capacitor #tutorials #tutorial #how-to #robertssmorgasbord

[@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 😅

[@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.

[@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.

[@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!

[@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.

[@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

[@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.

[@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.

[@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).