Product specifications

R01AN0168ED0101 Rev. 01.01 39

Application Note

Chapter 7 Performing Zero Point Detection

Figure 7-3 Reaching the Zero Point

In the best case, the induced voltage is slightly below the selected analogue

reference level, when the ZP is reached.

If this is not the case, the reference level should be selected such, that it is by

one selection step lower than the induced voltage, even if the ZP is reached.

The remaining detection of the level in detail then has to be perfomed by using

the digital filtering features of ISM.

(3) Definition of the Measurement Window using the Blanking Time

In general, ISM provides two options (which can also be combined), to set the

timing of the measurement window: The

Blanking Time and the ZPD table

itself.

The

Blanking Time is an additional delay, which can be applied optionally after

a measurement start trigger (

ZMTn set in the ZPD table).

Using the

Blanking Time allows a delayed measurement start in a certain

range, so that the self-induction phase of the coil and other undesired noisy

phases can be skipped (blanked out).

The

Blanking Time can be defined by the setting ZBTn for each physical

channel individually. The value of

ZBTn represents the number of

Measurement Cycles

to wait, until the measurement phase is started.

The measurement phase then is shortened in its beginning by the

Blanking

Time

The following figure shows the waveform of the induced voltage, while the ZP

is not yet reached, and how the electrical parameters and delays can be set to

define the measurement window.

Zero Point not

yet reached

Zero Point

reached

Reference

Level

See 7.2.2 “ZPD Measurement Cycles” for details.