6.2 An intuitive explanation of Counts

Counts is a value used by many in the capacitive touch industry, but understood by few. In this section, we’ll provide an intuitive explanation based upon an example.

As we saw, the value of Counts is proportional to the size of the electrode’s capacitance, Cx. As you recall from the previous chapters, the value of the electrode’s capacitance changes when conductive elements interact with the electrode. As a matter of fact, when this happens, the capacitance of the electrode increases, as does the value of Counts. Controllers leverage this phenomenon to detect the presence of conductive elements in the vicinity of the sensor, using the value of counts.

We define delta-counts as the difference between the touch and the no-touch states. The controller compares delta-counts to a given threshold value to determine if the sensor is touched by a conductive object or not.

Let’s consider a theoretical example of a circuit like the one in Figure one, with six sensors connected to it. Suppose that a conductive object touches sensor 2, another hovers slightly above sensor 4 and another hovers a greater distance above sensor 6. Sensor 1 has no objects in its environment, while sensors 3 and 5 have non-conductive objects in their respective environments, as summarized in Table 1.