oil transformer level circuit

[Vicky Susanto]

Dear All,
I want to make a level sensor for oil transformer, I just need 3 position that is Low,Med and High. I need some advice how to do it. And I have some suggestion from internet about this method that is :
1. using switch with ball or reed switch, but there is more difficulties in installation because of the space.
2. using capacitive sensor, but I dont know how to make this circuit> I've tried with LM555 and it didn't work. or maybe any suggestion about this from others.
any suggestion will be gratefully thanks..

thank you

 

[nandhu015]

Capacitive sensor is good option.
Show your circuit which you tried with 555, we will find what is wrong with it

 

[Vicky Susanto]

https://obrazki.elektroda.pl/90_1289369135.jpg
I only use the 555 for astable multivibrator.
I made greater Ohm for the RA and RB. And I make small to the C1 about 20 pF Then I made parallel connection between C1 and CX ( probe that touch the oil). then I read the freaquency of the output.
Or maybe my schematic is wrong.
I assume that when the oil is between my probe (plate) then the capacitance is higher, then it will make the frequency more slower.
Is it wrong ar what?

Thank you

 

[nandhu015]

The concept of capacitive sensor is the output frequency of the 555 varies according to the level of oil in the tank.

The main thing you have to do is to ensure that capacitance of the probes should vary to a readable values.

First check the capacitance of the probes with a capacitance meter and ensure it varies to the required limits.

 

[Vicky Susanto]

I tried to check the capacitance with my capacitance meter,I try to use a 1 cm x 1 cm (made from blank PCB). I know that air dielectric is 1 and oil transormer dielectric is 2.2 . With a resume of C = K *A /D ( which, K = Konstant dielectric, A = area, D=distance). When I measure the capacitance it seem same with in the air. Can you give me the resume for this Capacitance? how about my circuit? it is wrong or not?I dont need to count the level of oil, just need to know with 3 parameter ,Low,Med and High. so I will need to make 3 sensor.The problem is I only get a small hole to take the sensor inside, maybe about 7 mm in diameter. and the distance ( height for the sensor is 7,5 cm. I use 5V for supply. is this enough?

---------- Post added at 07:58 ---------- Previous post was at 07:41 ----------

How about hall effect sensor? using with UGN3503 and I make a magnet.
Or how about the reed switch?