afe4400SPO2EVM voltage on GUI

Viney Chaddha

Other Parts Discussed in Thread: AFE4400

Hello,

I am very new to this. Can someone tell me what does the voltage on the GUI measurement page mean, the grapgh is in Volts for the LEDs

over 9 years ago

0 Amy Schnoor over 9 years ago

TI__Mastermind 18275 points

Viney,

Thank you for you inquiry of the AFE4400. We hope to have an answer back to you shortly.

0 Amy Schnoor over 9 years ago in reply to Amy Schnoor

TI__Mastermind 18275 points

Viney,

A single, 22-bit ADC converts the sampled LED2, LED1, and ambient signals sequentially. Each conversion provides a single digital code at the ADC output. The voltage on the GUI are the codes from the ADC converted to volts. The ADC_RDY signal goes high each time the contents of the LED registers are updated. For more information on the codes from the ADC please refer to the datasheet (link below).

http://www.ti.com/lit/ds/symlink/afe4400.pdf

Here is the link to convert codes to volts:

http://e2e.ti.com/support/applications/high_reliability/f/30/t/340964.aspx

0 Viney Chaddha over 9 years ago in reply to Amy Schnoor

Prodigy 20 points

I am seeing a lot of noise getting captured on the channels. this was not the case earlier and i use to see a very clean graph earlier. now the graph is very noisy. Could some one please let me know why is this the case?

Regards

Viney Chaddha

0 Praveen Aroul over 9 years ago in reply to Viney Chaddha

TI__Mastermind 49176 points

Hello Viney,

In order to help you debug the problem can you provide the waveform plots of the noisy data?

We have come across situations where there was power line noise riding on top of the signal of interest.

If you are also noticing the power line noise, refer to the E2E post below for few pointers to mitigate the problem.

http://e2e.ti.com/support/applications/high_reliability/f/30/p/311809/1089207.aspx#1089207

Regards

Praveen.

0 viney chaddha1 over 9 years ago in reply to Praveen Aroul

Expert 1280 points

Praveen,

Please find attached the waveform plot. I did everything as suggested but am still getting the noise even with a very short cable. I am using DCM03 sensor to collect the data.

Regards

Viney Chaddha0654.with bat power.docx

PS: How do you insert pictures in this dialogue box

0 Praveen Aroul over 9 years ago in reply to viney chaddha1

TI__Mastermind 49176 points

Viney,

In the waveform plot, the notch filter was not enabled. Could you repeat the experiments by enabling the 50/60Hz notch filter on the GUI?

Look at the FFT of the output data and see if the noise is spread over frequency or concentrated in a single tone or set of tones.

Regards

Praveen.

P.S. You cannot directly insert pictures. You can insert a saved image from your computer by clicking the 'Insert image' icon from the menu in the editor window.

0 viney chaddha1 over 9 years ago in reply to Praveen Aroul

Expert 1280 points

Praveen,

After repeating with the battery powered laptop the 50 Hz noise wasn't present. If I ook at the FFT the frequency of the signal is 5 Hz and multiples of 100 Hz. What is the source of these frequencies, especially the 5Hz noise

see the graphs5125.with bat power.docx

Also why do I see a lot of DC shift in the signal?

Regards

Viney Chaddha

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afe4400SPO2EVM voltage on GUI