Capacitive liquid level measurement circuit

Capacitance/C position IJ quantity is to directly convert changes in material level into changes in electrical parameters, and then convert the electrical parameters into unified electrical signals for transmission,
processing, display, etc. According to different electrical parameters, it can be divided into: resistive type, capacitive type and inductive type, etc. Now the capacitive type will be introduced.
  We know that the capacitance of the simplest capacitor
    is known from the above formula. Corresponding capacitance sensors can be made by changing d, E or changing A. The capacitive level meter mainly consists of
a capacitive sensor and a measurement circuit .
    Capacitive sensors are generally made based on the principle of changing the dielectric constant E. Figure 6-38a and b show the capacitive liquid level sensor and measurement circuit. A cylindrical capacitor is set in
the solution to be measured. When the plate distance d and the area A are fixed, the capacitance is C. It will
change with the dielectric constant E of the medium between the plates . Assume the dielectric constant of the liquid is ￡, and the dielectric constant of the gas is e2. Generally, E, >ez. When the liquid level rises, the total dielectric constant
increases. Therefore, the capacitance G increases accordingly. On the contrary, when the Rang level decreases, E decreases. c, then decreases. Therefore,
the liquid level in the container can be known by measuring the change in C. Figure 6-38b is the capacitance measurement circuit , and G is the reference arm capacitance. '