ADS122S14EVM-PDK: Register settings for 3-wire RTD

ttd

Mastermind 9355 points

Part Number: ADS122S14EVM-PDK
Other Parts Discussed in Thread: ADS124S08EVM

Dear Technical Support Team,

Do you provide config file(.cfg) for register settings of 3-wire RTD with two IDACs ?

Previsou version , ADS124S08EVM GUI has scripts for each settins such as 3-wire RTD with two IDACs.

It is easy for me to set register setting.

Shoud I connect between RTD_B and RTD_C directly?

Best Regards,

ttd

3 months ago

0 Bryan Lizon86 3 months ago

TI__Guru 59031 points

HI ttd,

Answers to your questions:

We don't have a config file for different RTD configurations. However, we do have example code on our github page: https://github.com/TexasInstruments/precision-adc-examples/tree/main/devices/ads122s14

You can also reference Table 2-2 in the EVM user's guide for the proper connections. Or you can use the image you provided from the user's guide for the appropriate settings: the

MUXP = AIN1
MUXN = AIN2
IDAC1 = AIN0
IDAC2 = AIN3
REFP = AIN4
REFN = AIN5

Then you will need to select the appropriate PGA gain, data rate, and IDAC current output for your application.

And yes, you will need to add an external jumper wire between RTD_B and RTD_C in addition to connecting the RTD as shown

-Bryan

0 ttd 3 months ago in reply to Bryan Lizon86

Mastermind 9355 points

Hi Bryan,

Thank you for your reply.

I got expected result with your configuration and IDACs=200uA , PGA=1.

IDAC1 ＋ IDAC2 = 400uA flows via R20=4kΩ, it measn 1.6V for the external reference voltage.

RRTD = RREF • Output code / (2^22 • Gain) = 4kΩ * 114836 / 2^22 =109.52Ω (24.7℃ from PT100 table).

ADS124S08EVM has 3-wire with two IDAC (High side reference), however ADS122S14EVM has low side reference.

Is there any pros and cons between them?

Best Regards,

ttd

0 Bryan Lizon86 3 months ago in reply to ttd

TI__Guru 59031 points

Hi ttd,

We have a lot of content that explains RTD measurements and their pros / cons:

Training videos (11x): https://www.ti.com/video/series/precision-labs/ti-precision-labs-analog-to-digital-converters-adcs.html?videoId=6330516233112
App note: https://www.ti.com/lit/pdf/sbaa275

-Bryan

Data converters

Data converters forum

ADS122S14EVM-PDK: Register settings for 3-wire RTD