ADS1261EVM: ADS1261EVM

vadim piskun

Part Number: ADS1261EVM
Other Parts Discussed in Thread: ADS1261, ADS124S08EVM

Hi,

I would like to configure this board for 2 wire RTD measurements. The data sheet provides 3 wire schematics. is this configuration ok for 2 wire

thanks vadim

9 months ago

0 Bryan Lizon86 9 months ago

TI__Mastermind 40511 points

Hi vadim piskun,

I would check the polarity of the REFx signals in the ADS1261 datasheet to make sure you are connecting the reference resistor to the correct pins. You don't show a ground connection in your drawing (assuming you use a low-side reference resistor), so it's not clear which pin is being used for REFP and which is for REFN.

You also don't show a current source connection in your diagram, nor is there a connection between the RTD and the reference resistor

-Bryan

0 vadim piskun 9 months ago in reply to Bryan Lizon86

Expert 2230 points

Hi Bryan,

thanks for your support! Figure 1.4

https://www.ti.com/lit/an/sbaa275a/sbaa275a.pdf?ts=1704861407709&ref_url=https%253A%252F%252Fwww.google.com%252F

shows two wire connections. I modified schematic accordingly. Do i use correctly IDAC1 and not IDAC2?

thanks vadim

0 Bryan Lizon86 9 months ago in reply to vadim piskun

TI__Mastermind 40511 points

Hi vadim piskun,

It looks like you are trying to setup a high-side reference, similar to the top right image you included (the bottom right shows a low-side reference). In this configuration, AINCOM will be the current source, correct? If so, this should work

However, you still need a connection to ground so the current has a path to flow. Right now there is no path to ground for the current coming out of AINCOM, so neither the RTD nor the reference resistor will be biased

And, since this is a high-side, you need to add a bias resistor to the bottom of the RTD. See section 2.2 in this document for a discussion about why that bias resistor is needed: https://www.ti.com/lit/an/sbaa275a/sbaa275a.pdf?ts=1705101517845

-Bryan

0 vadim piskun 9 months ago in reply to Bryan Lizon86

Expert 2230 points

Thanks Bryan!

Is there by any chance s predefined script for RTD measurements?

thanks vadim

0 Bryan Lizon86 9 months ago in reply to vadim piskun

TI__Mastermind 40511 points

Hi vadim piskun,

I believe there are, but I am not able to check at the moment. You would select from the predefined scripts similar to what is done for the ADS124S08EVM.

You can always copy the command flow from the ADS124S08EVM GUI as well

-Bryan

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