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Firmware implementation

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3.4

Multi-acquisitions and HF noise rejection

To improve the measurement accuracy and reject high frequency (HF) noise, it is necessary

effectively “touched”. This number of acquisitions is calculated using one of two variables:

the first one is fixed and dependent on the MCU core and the other one is configurable

(through the configuration file of the TS library).

Figure 9.

Types of acquisitions

Note:

The configurable acquisition number (N) can be set differently in the configuration file of the

TS Library for the single-channel keys and for the multi-channel keys.

The figures below illustrate examples of HF noise rejection. If the acquisition number (N) is

set to 4, a complete acquisition of one electrode will consist of 4 correct “burst groups”

(BGs). The word “correct” means that all measurements inside the group remain between a

minimum and a maximum limit.

These example show different scenarios depending on the level of noise. The green line

Figure 10 shows an example where there is no noise and no measurements are rejected.

In this example, all the measurements inside each burst group pass. The complete

acquisition is done quickly.

Figure 10.

Example 1

t

“Touched effect”

Configurable acquisition number (N)

Fixed (“burst group”)

Start electrode acquisition

Acquisition OK

BG1

Pass

BG3

Pass

BG2

Pass

BG4

Pass