DDC264: RTD sensor array

Oliver Barry

Part Number: DDC264

Hello,

I am designing a large RTD sensor array (50+ PT1000s). I am planning on using two of these ADC daisy chained together to accomodate for my two measurement inputs and having the RTDs connected in the 4-wire configuration using a common excitation (+) and (-) for the entire array. I am looking for design/suitability advice regarding this situation. Is this ADC a good choice for this application? Will having an external excitation source hugely affect measurement accuracy? Can I connect the excitation (-) directly to the recommended reference buffer circuit?

over 3 years ago

0 Nick Zahabizadeh over 3 years ago

TI__Expert 6555 points

Hi Oliver,

We have your ticket viewed and we'll be taking a look. Please give 24 hours for a response.

Kind regards,
Nick Z.

0 Oliver Barry over 3 years ago in reply to Nick Zahabizadeh

Prodigy 40 points

Cheers thanks

0 Eduardo Bartolome over 3 years ago

TI__Expert 4680 points

Hi Oliver,

Not sure if you noticed that this device is a current input ADC. The inputs (single ended) are virtual grounds albeit with a sizeable input impedance (kOhms, depending on the input range).

So, if I understand right what you are trying to do, this probably wouldn't work, isn't it? If you just wanted to measure a resistor, you could actually connect it in series between a supply/reference and the input of the DDC. The current measured would tell you the value of the resistor. There are probably other variations of that approach but not sure you would get all what you usually get with the 4-wire configuration (differential measurement, cable resistance not affecting the measurement, etc). I haven't seen it done with a DDC. Would have to think about it but probably a no-go?

Regards,
Eduardo

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DDC264: RTD sensor array