AN2866

Contactless measurement method

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Figure 16.

Oscilloscope views

Figure 17 provides a synthesis of the measurements made. It is obtained by plotting

characteristic points for different frequencies at a given voltage. Each resonance trace

represents a synthesis for a definite voltage transmission.

Figure 17.

Synthesis of resonance traces for different voltages

Note:

1

Without a tag: the scope trace must be as flat as possible. It is the reason why the antenna

connected to the generator must not be tuned at 13.56 MHz.

2

With a tag on the antenna: the scope trace shows the resonance of the system without any

contact.

Transmission: 0.2 V sine (13.56 MHz)

Reception: 0.1 V sine (13.56 MHz)

Transmission: 0.2 V sine (14.3 MHz)

Reception: 0.2 V sine (14.3 MHz)

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0

0.5

1

1.5

2

2.5

3

3.5

12.5

13

13.5

14

14.5

100 mV

200 mV

300 mV

400 mV

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