Other Parts Discussed in Thread: ADS1220, , ADS124S08
Tool/software:
Dear TI Technical Community,
As throughphully described in refrences below [1-3], estimating total error of RTD-based temperature measurment using precise ADCs required initial error (offset error, gain error, INL, noise) and over-temperature (offset drift, gain drift) parameters of the ADC. These parameters can be easily found (pls see table 1) in well-known ADC's datasheet such as ADS124S0x, ADS1220, ADS114Sx, etc. At the end, the total errors can be calculated by considering each parameters and converting to the same unit (uV).
However, when it comes to ADS1282-SP, finding these parameters is challenging (pls see table 2) and I am not confident regarding some of them extracted from datasheet. I would really appreciate looking my questio (below after second table) and give me some assist.
Table1. ADS124S08 Error Parameters
| Error Type | TYP | MAX | Unit |
| Offset error | 20/gain | 120/gain | uV |
| Gain error | 40 | 120 | ppm |
| ADC INL | 2 | 15 | ppm_FSR |
| ADC Noise | 0.45 | 2.9 | uV |
| ADC Offset drift: | 15 | 200 | nV/°C |
| ADC Gain drift: | 1 | 4 | ppm/°C |
Table2. ADS1282-SP Error Parameters.
| Error Type | TYP | MAX | Unit |
| Offset error | ?? | ?? | ?? |
| Gain error | 1 | N/A | uV |
| ADC INL | N/A | 0.0170 | %FSR |
| ADC Noise | ?? | ?? | ?? |
| ADC Offset drift: | N/A | 750 | uV |
| ADC Gain drift: | –1.5% | –1.0% |
My question:
- Two different "offset error" can be found in the datasheet. One is 0.0170%FSR and another is Offset error after calibration => TYP:50, MAX:200 uV. Which one should I used?
- How can I estimate maximum error when maximum gain error is not available (I did'nt find)?
- I also considered Input-Referred Noise as ADC noise. is it right? The SNR is given for different GAIN and DATA_RATE in datasheet, so then I can calculate the ADC noise using equation SNR=20log(FSR_RMS/N_RMS) where N_RMS is Noise RMS (input-reffered).
- ADC gain drift is mentioned -1.5% and -1.0%. How can I convert them to uv? Percentage of WHAT ??!!
References:
[1]: A Basic Guide to RTD Measurements: https://www.ti.com/lit/an/sbaa275a/sbaa275a.pdf?ts=1735027453025
[2] : Estimating total error in RTD measurement systems TI Precision Labs – ADCs: https://www.ti.com/content/dam/videos/external-videos/en-us/10/3816841626001/estimating-total-error-RTD-measurement-systems.mp4/subassets/estimating-total-error-RTD-measurement-systems-presentation.pdf
[3]: Estimating total error in RTD measurement systems TI Precision Labs – ADCs: www.youtube.com/watch
[3]: ADS1282-SP Datasheet: https://www.ti.com/lit/gpn/ads1282-sp
