ADS1235EVM: ODR Selection for ADS1235 EVM

Nimit Vachhani

Part Number: ADS1235EVM
Other Parts Discussed in Thread: ADS1235

Tool/software:

Greetinge Everybody,

I am using ADS1235-EVM. I have connected load cell signal + to AIN0 and signal - to AIN1 and Sense + to REFP0 and Sense - to REFN0. Default value of R in the evm for differential input is 100 Ohms which i have changed to 1000 Ohms. I am giving 5 VDc excitation to load cell. After this setup my Fcdif comes to 9.216 KHz and i am confused about selecting the ODR for the ADC. Any guidance for output data rate (ODR) selection for noise removal will be of great help. My main aim is to remove anti-aliasing as much as possible.

Thanks.

2 months ago

0 Bryan Lizon86 2 months ago

TI__Guru 52296 points

Hi Nimit Vachhani,

The data rate is usually determined by your system requirements, not the anti-aliasing filter i.e. how fast does your system need to sample, what is the noise performance, etc. Then you would pick the AA filter components in part based on the data rate (but mainly the modulator frequency). So I don't really have any guidance to your question because I don't think this is a great way to select a data rate.

If you have more information to share about what you are trying to do please provide it

-Bryan

0 Nimit Vachhani 2 months ago in reply to Bryan Lizon86

Prodigy 90 points

Greetings,

I am trying to achieve similar task as posted in the question below

https://e2e.ti.com/support/data-converters-group/data-converters/f/data-converters-forum/1374205/ads1235-digital-filtering-and-different-measurement-rate?tisearch=e2e-sitesearch&keymatch=ads1235#

I also want to implement different sample rates and cut-off frequencies.

0 Bryan Lizon86 2 months ago in reply to Nimit Vachhani

TI__Guru 52296 points

Hi Nimit Vachhani,

Today is a holiday in the US, we will respond to your question next week. Thanks for your patience

-Bryan

0 Bryan Lizon86 2 months ago in reply to Bryan Lizon86

TI__Guru 52296 points

Hi Nimit Vachhani,

What specifically are you trying to do? The exact same thing as in the post you linked to? In that case, the user had already selected a data rate, so this is different than what you are asking.

Again, I don't think it makes sense to pick an AA filter cutoff frequency and then a data rate

-Bryan

0 Nimit Vachhani 2 months ago in reply to Bryan Lizon86

Prodigy 90 points

Ok.. I have replaced the default resistors that come in evm for differential input to 1K instead of 100 Ohm. Now the differential cutoff frequency according to the formula comes to 9.216 KHz. I want sampling rates of 20 Hz, 50 Hz, 100 Hz and 200 Hz and cutoff frequency of 0.5 Hz, 2 Hz, 15 Hz and 25 Hz. In this scenario what to do ?

0 Bryan Lizon86 2 months ago in reply to Nimit Vachhani

TI__Guru 52296 points

Hi Nimit Vachhani,

The digital filter bandwidth for each data rate and filter options is shown in the table below, which is from the ADS1235 datasheet.

Also note that there is no option for 200 SPS.

-Bryan

0 Nimit Vachhani 2 months ago in reply to Bryan Lizon86

Prodigy 90 points

Noted. Thanks. I will use 400 sps ...

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ADS1235EVM: ODR Selection for ADS1235 EVM