Capacitance Transducer?

Question

Any ideas of where online to find a graph that shows the capacitance vs displacement of a capacitance transducer?

Any general capacitance transducer

Answer 1

You can make such a graph yourself if you know the capacitance at one displacement.

For parallel plate capacitance transducers, capacitance is inversely proportional to the distance between the transducer plate and a nearby conductive "ground" plane. This is an hyperbolic function of separation that goes to infinity as the separation approaches zero. So, if you reduce the separation to one-half what it was initially, the capacitance will double. Reduce the separation to half of that new distance and the capacitance doubles again. And so on, until the plates are too close together to hold off whatever voltage is applied across the plates to measure the capacitance.

Strictly speaking, this formula only applies to plates with infinite surface area. Real plates will have a "fringe effect" at their edges that will prevent them from obeying the inverse distance separation rule perfectly, but this becomes less of a factor for small displacements about a nominal initial "zero" position. Even though the actual capacitance versus separation relationship is hyperbolic, a small enough segment of any curve is approximately linear.

See the site for a fairly clear practical discussion of capacitors.

Answer 2

It is important to know the basics of a parallel plate capacitor. Being the simplest form of a capacitor, it has two parallel conducting plates that are separated to each other by a dielectric or insulator with a permittivity of Ε (for air). Other than paper, vacuum, and semi-conductor depletion region, the most commonly used dielectric is air.

Due to a potential difference across the conductors, an electric field develops across the insulator. This causes the positive charges to accumulate on one plate and the negative charges to accumulate on the other. The capacitor value is usually denoted by its capacitance, which is measured in Farads. It can be defined as the ratio of the electric charge on each conductor to the voltage difference between them.

The capacitance is denoted by C. In a parallel plate capacitor, C = [A*Er*9.85*1012 F/M]/d

A – Area of each plate (m)

d – Distance between both the plates (m)

Er – Relative Dielectric Constant

The value 9.85*1012 F/M is a constant denoted by Eo and is called the dielectric constant of free space.
From the equation it is clear that the value of capacitance C and the distance between the parallel plates,d are inversely proportional to each other. An increase of distance between the parallel plates will decrease the capacitance value correspondingly. The same theory is used in a capacitive transducer. This transducer is used to convert the value of displacement or change in pressure in terms of frequency.

https://www.electrikals.com/products/rc-meters/transducers?cnid=e767e5db4d670a59014e203403f41af2&cid=620&page=1&pagesize=20

Answer 3

That sounds like the specification sheet for a particular transducer.