How to measure capacitance of a capacitive sensor?

Discussion in 'General Electronics Chat' started by kynix, Jul 18, 2016.

  1. kynix

    Thread Starter New Member

    Jul 18, 2016
    I've started working on capacitive sensors and finally got one ready(which is concentric cylinder type) but now I need to test it. I have few doubts:

    1. Can I calculate the value of capacitance without any instrument? May be just with an analytical formula.
    2. What difference I may get in the values of capacitance produced from this formula and from an LCR-meter?
    3. [​IMG]
  2. Papabravo


    Feb 24, 2006
    The formula is meaningless scribbles without a drawing to relate the various quantities. Your picture is fuzzy and overlapping my first response box. Why would you be so rude as to do such a thing? What is the problem with using measurement techniques to measure the thing?
  3. Techno Tronix


    Jan 10, 2015
    You can use some analog Techniques to find capacitance of a capacitive sensor.
  4. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    You can use something as simple as a 555 in a stable mode to produce a frequency dependent on the capacitance of the sensor. Knowing the resistor values you can compute the capacitance from the measured frequency.

    While not my first choice I worked on a unit using a 555. The level sensor was based on two concentric tubes where the level of the liquid changed the dialectic and thus the capacitance based on the level of the liquid. Do note we calibrated the sensor when placed into use, and it will require recalibration if the liquid type changes.

    A small micro controller did the frequency measurement and provided a 0-5 volt signal indicating the level.