RTD (PT100) DAS

Mostafa Elwakeel

Other Parts Discussed in Thread: ADS1148, ADS1248

hello all ,

i want to measure four RTD sensors (pt100 ) using single chip can i do this with ADS1148 ?? do i need external reference also if i need ADS1148 ??

i work in extramly sensitive price application so do you recommend any other option to make reduction for cost ??

Thank you

Mostafa Elwakeel

over 14 years ago

0 Tom Hendrick over 14 years ago

TI__Guru**** 180941 points

Hi Mostafa,

Yes - you can read four RTD's with the ADS1148 - there is an internal reference with this device so you would not need to supply an external reference.

0 Mostafa Elwakeel over 14 years ago in reply to Tom Hendrick

Prodigy 105 points

hello Tom ,

Thx for your reply . Can you send me schematic for such connection of four RTD (Pt100) with ADS1148 ??

Thanks again

Mostafa

0 Tony Calabria over 14 years ago in reply to Mostafa Elwakeel

TI__Mastermind 43915 points

Hi Mostafa,

This post may help you.

http://e2e.ti.com/support/data_converters/precision_data_converters/f/73/t/71027.aspx

A 3 wire implementation is probably the way to go if you want to use 4 separate RTDs and want to use the Rbias resistor across the reference. Otherwise, just use the internal reference as you convert the channels. Now note that the ADS1248 has a common mode input range restricting you from running the ADS1248 single ended using a single supply, so make sure that all your Pt100 inputs you are within the CM input limits. This may require you to add a small resistor from the AINN input to ground to bias up the analog inputs into the CM input range.

Regards,

Tony Calabria

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RTD (PT100) DAS