AFE4300 calibration steps to perform the impedance measurement

Artjom Emter

Other Parts Discussed in Thread: AFE4300

Hello!

I have questions regarding the slope and offset calculating in FWR and IQ mode. The explanation and example in Section 2 is ambiguous.

If I want to use FWR mode for 3 different frequencies like 5 kHz, 50 kHz and 100 kHz, so should I measure the resistance of reference resistors only onetime unter 64 kHz and ADC 64 SPS?
What is the frequency and settings for measure of I and Q voltage of the reference resistors Rx and Ry in the Step 2 Section 2.2? If I want to use IQ mode for frequencies like 8 kHz and 16 kHz..
In the Step 3 do I calculate slope and offset, is equation for slope_IQ = (Ry - Rx) / (Mag_Ry – Mag_Rx) and offset_IQ = Rx – slope_IQ x Mag_Rx ? Where can I find the equation for slope and offset?

In the example for IQ you use the slope value from FWR mode measurement, is it correct?

Thanks

over 10 years ago

0 Praveen Aroul over 10 years ago

TI__Mastermind 49906 points

Hello Artjom,

We have received your inquiry regarding the AFE4300 and hope to have some answers back to you shortly.

0 Amy Schnoor over 10 years ago in reply to Praveen Aroul

TI__Mastermind 18285 points

Artjom,

Sorry for the delay.

1. When using FWR mode you will want to recalibrate each time you change frequencies.

2. In section 2.2 there is no specific frequency. The steps in section 2.2 need to be repeated for every frequency. The GUI will do this for you though. This is shown in section 3.1 Figure 10.

3. Your slope and offset equations are correct.

0 Artjom Emter over 10 years ago in reply to Amy Schnoor

Prodigy 30 points

Hi Amy,

I am using the AFE4300 directly with a small 8-bit MCU (even without GUI). Is there measurement ranges what of 4 reference resistance to take are the best?

Best Regards
Artjom

0 Amy Schnoor over 10 years ago in reply to Artjom Emter

TI__Mastermind 18285 points

What are the impedance ranges you will be measuring in your application?

0 Artjom Emter over 10 years ago in reply to Amy Schnoor

Prodigy 30 points

from 200 up to 950 Ω

0 Amy Schnoor over 10 years ago in reply to Artjom Emter

TI__Mastermind 18285 points

OK. Then the calibration resistors that we chose for our EVM should work for your application as well.

R56-700 Ohms
R57-950 Ohms
R58-100 Ohms
R59-200 Ohms

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AFE4300 calibration steps to perform the impedance measurement