ADS1220EVM: Cant generate constant current

Felix Kotschenreuther

Prodigy 20 points

Part Number: ADS1220EVM
Other Parts Discussed in Thread: ADS1220, ADCPRO

Tool/software:

Hi,

im evaluating the ADS1220 to measure a unknown resistor with a constant current.

I have connected a resistor to AIN0 and AIN1. These are the ADCPro Settings

my jumpers are connected like they are recommended in the users guide:
JP3 3.3V, JP7 Short, JP8 Short.

I also tried setting JP1 and JP2 to short but these didnt help either.

From reading the circuit diagramm and understanding the ADS1220 my understand would be that the ADS recieves the AVDD Voltage and internally outputs the constant current to AIN0, so JP1 and JP2 aren't necessary.

Sadly im not getting any voltage readings, that make sense.

Did I miss something? I put a multimeter in series on AIN0 and AIN1 but it didn't detect any current either.

3 months ago

0 Bryan Lizon86 3 months ago

TI__Guru 52496 points

Hi Felix Kotschenreuther,

Can you send us a photo of how you have connected the resistor to your board? Or at least send us a connection diagram so we can review?

-Bryan

0 Felix Kotschenreuther 3 months ago in reply to Bryan Lizon86

Prodigy 20 points

Hi, these are the three configurations I tried (A, B, C)

B would be what it says in the guide for a 2 Wire RTD.

0 Bryan Lizon86 3 months ago in reply to Felix Kotschenreuther

TI__Guru 52496 points

Hi Felix Kotschenreuther,

Thanks for providing the requested information

In your drawings and in the resistor connections you made on the EVM, where is the current supposed to go? How does it return to ground? It looks like you have an open circuit in all of your drawings, please correct this

You can reference our RTD design guide for more information: https://www.ti.com/lit/an/sbaa275a/sbaa275a.pdf?ts=1750959992149&ref_url=https%253A%252F%252Fwww.google.com%252F

-Bryan

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ADS1220EVM: Cant generate constant current