Compare the RF Field Strength Measurement Between the TCL3 and the Picoscope

Updated Oct 23, 2019

Reported In

Hardware

  • Micropross Accessories

Other

Hardware : MP500 TCL3, Picoscope

Software : MPManager 3

Issue Details

I would like to compare the RF field strength measurement between the TCL3 and the picoscope.

How can I do that?

Solution

It's difficult to compare the RF field strength measurement between the TCL3 and the picoscope because this measurement is very sensitive. We have to make sure that we are measuring exactly the same thing with the TCL3 and with the oscilloscope. The best would be to use an ISO bench but you can also do this comparison using a generic NFC reader.

Here is the procedure to compare the measurements using the TCL3 own generated field :

1. Make sure that the probe compensation is done: you have to attach the picoscope probe to the hook and the crocodile clip to any ground connector:

With this configuration, you are supposed to get the following signal on channel A:

 

The signal must be square without any distortion.

2. Use a cable to connect the "analog in" connector of the TCL3 to the calibration coil. 

3. Attach the oscilloscope probe to the calibration coil:

Here is a zoom on the calibration coil:

As you can see on the picture, the crocodile clip of the probe is twisted around the oscilloscope probe. What is essential for the measurement is the position of the calibration coil. We advise you to attach the calibration coil to the ISO bench.

4. Before starting the measurement, it is necessary to power on the field strength.

For that, go to the script window of MPManager and launch an easy script containing only the command “Contactless Common: Power On”.

5. Perform an RF measurement with the TCL3 (tab "test", sub tab "RF measurement").

6. Perform a measurement with the oscilloscope using the Vpp unit.

7. According to the ISO 14443 standard, the open circuit calibration factor for the calibration coil 1 is 900 mV (peak-to-peak) per A/m. Which means:
1 A/m = 0.9 Vpp

8. You can now compare the RF field strength measurement between the TCL3 and the picoscope