How does this sensor measure liquid level?

I am familiar with a method of estimating the liquid level which is done with two plates of a large capacitor -- one plate on each side of the beaker/container. As the liquid level rises, the dielectric changes, so the capacitance between the two plates changes. Measure the capacitance, and you can calculate the liquid level. All good.

But just now, I found this interesting product (also capacitive based), which seems to measure the liquid level with the plate/sensor installed on just ONE side of the container -- I don't get how this is possible!
The sensor: http://www.sensortechnics.com/en/products/liquid-level-sensors-and-switches/capacitive-level-sensors/clc/
Datasheet: http://www.sensortechnics.com/cms/upload/datasheets/DS_Standard-CLC_E_11663.pdf

Does someone understand how this works?

The pads on the sensor couple capacitively to the liquid (has to be water I'm guessing), and thence
indirectly to each other. So the capacitance between different conductors on the sensor will vary
as the liquid level alters.

@MarkT, But there appears to be only one plate/set-of-pads (as opposed to two plates with one on each side of the container), so what do you mean, "to each other"?

When the water rise the senser detect a change in a capacitance because the water acts like a dielectric material.It 's much like a big cap.
Reading the capacitance can give you the water level using some calculations.
Search for capacitive sensor and you will find a more tecnical answer.

That doesn't answer my question. I understand how this type of measurement works between two capacitive plates, as I stated in my question.

But how did they do it with what appears to be only ONE capacitive side/plate/pad placed on the container?

HugoPT:
Reading the capacitance can give you the water level using some calculations.

it would appear that the sensor comprises a number of discrete pads; if so, the capacitance between pads is a function of the spherical dielectric

Hmm, I think you might be right. Perhaps they use the bottom-most electrode/pad as one plate of the capacitor, and based on the capacitance measured at the various other pads, they can infer the volume of the dielectric, which I guess would be the spherical analogue of a pair of opposite-facing capacitor plates.
I want to try to make one of these and see how accurate it will turn out.

jackrae:
it would appear that the sensor comprises a number of discrete pads; if so, the capacitance between pads is a function of the spherical dielectric

It appears to be a capacitive displacement sensor.

Capacitance is an electrical property which is created by applying an electrical charge to two conductive objects with a gap between them. A simple demonstration is two parallel conductive plates of the same profile with a gap between them and a charge applied to them.

There are two general types of capacitive displacement sensing systems. One type is used to measure thicknesses of conductive materials. The other type measures thicknesses of non conductive materials or the level a fluid.

A capacitive sensing system for conductive materials uses a model similar to the one described above, but in place of one of the conductive plates, is the sensor, and in place of the other, is the conductive target to be measured. Since the area of the probe and target remain constant, and the dielectric of the material in the gap (usually air) also remains constant, "any change in capacitance is a result of a change in the distance between the probe and the target.

Due to this proportional relationship, a capacitive sensing system is able to measure changes in capacitance and translate these changes into distance measurements.

The operation of the sensor for measuring thickness of non-conductive materials can be thought of as two capacitors in series, with each having a different dielectric (and dielectric constant). The sum of the thicknesses of the two dielectric materials remains constant but the thickness of each can vary. The thickness of the material to be measured displaces the other dielectric. The gap is often an air gap, (dielectric constant = 1) and the material has a higher dielectric. As the material gets thicker, the capacitance increases and is sensed by the system.

A sensor for measuring fluid levels works as two capacitors in parallel with constant total area. Again the difference in the dielectric constant of the fluid and the dielectric constant of air results in detectable changes in the capacitance between the conductive probes or plates.