ADS1235EVM: Data collection Questions

Hi Adam,

Seem my responses below.

Best regards,

Bob B

Adam Daluga said:

Part Number: ADS1235EVM

Hi,

I had some questions about the ADS1235

1. In the output to the data analysis window there are output values for

ADC0 and CRC0. What is  CRC0? 

 [Bob] CRC0 refers to the CRC response from the ADC for verification of the data by CRC check.  This is informational only.  Any calculation would have to be done manually.

2. When I use the collect data button in the Data Analysis screen, or when I submit a Collect n command from the script window

It always resets to delete all the previously received data.  I would  like to collect 19 sets of 20 data points to be able to change the input signal to cover the entire range of the input scale.

 Is there a way to write a script that will add data to the output but not clear the existing set?

 [Bob] Unfortunately no, there is no way to append data.  You would need to collect the data and save to a file each time.

3. I read through the calibration instructions but not sure I am following the part about using 95% for full scale by setting FSCAL[2.0]=3CCCCCh.

 

When you do that do you use a full scale input signal or so you need to use a 95% full scale input signal?

 [Bob] I would not use GANCAL, nor would I change the settings in the FSC registers.  The device is factory calibrated, so there is really little need to calibrate the gain.  As this is a confusing process, I would suggest not using it as most likely will cause more issues than it is worth.  The setting the FSC to 95% prevents clipping of the input signal should it be greater than 100% of the original factor calibration.  If you do the system gain calibration you apply a full-scale signal to the ADC inputs.

What are the commands to set the offset and the full scale, are they SYOCAL and SYGCAL? What is the SFOCAL self offset calibration used for?

[Bob] SYOCAL and GANCAL are system calibrations where the user must apply the appropriate settings for the calibration.  The SFOCAL applies an internal short to the ADC inputs to remove offset error due to the PGA and modulator.  I suggest that you use SFOCAL only.  The system calibrations require that you connect the appropriate input signals to the device.  This can be complicated as the offset calibration requires that the 0 input be placed within the input range of the ADC relative to the gain applied.  The system gain calibration is similar as you must apply the appropriate voltage.  I have personally not seen the need to use the system calibration in weigh scale applications as the scale must be calibrated relative to the load cell used which then becomes much easier to calibrate on codes within the scale range as opposed to the full-scale range of the ADC.  The scale range is often much less than the full-scale range by maybe a 1/4 or more where gain error is much less pronounced with respect to the ADC.

Thanks for the help,

Adam