Using the PC Software
4.6.2
Block Analysis Length
The histogram, RMS, and peak-to-peak calculations require a set of samples. These calculations are
updated with every group of samples received, and are performed on a block of the most recently
acquired (or averaged) samples.
The number of samples used is set using the Analysis points control. By default, this number is 100, but
can be changed at any time. This value also controls the RMS and peak-to-peak noise analysis lengths.
If the number of samples collected is not yet equal to the number of samples specified by the Analysis
points control, 0s are substituted for the samples not yet received.
In Analysis mode, the analysis can be reset using the button marked Reset analysis. This function clears
the internal analysis buffer. This button cannot be used outside of Analysis and Recording modes.
Analysis is automatically reset when Analysis and Recording modes are entered.
4.6.3
RMS and Peak-to-Peak Noise Analysis
The RMS and peak-to-peak noise analysis calculations are performed in exactly the same way as they are
in the ADS1x31REF firmware, as described in
. Each calculation can be displayed in units of
volts, codes, or bits, as on the board. See
for detailed descriptions of the calculations.
The number of samples used in each calculation is set using the Analysis points control. By default, this
number is 100, but can be changed at any time. This control also controls the histogram length.
4.6.4
Displaying Volts
When units of volts are displayed, the program must have a value for the reference voltage applied to the
installed ADS device to properly calculate the voltage. Because this voltage cannot be measured using
the ADS1x31REF, it is set manually using the Vref control.
The value of Vref defaults to 5V, because the reference is normally taken from the 5V power supply. If a
different reference voltage level is used, the value of Vref should be changed to reflect the different level,
so that voltage calculations are performed correctly.
The Vref control also affects voltages recorded in Record mode.
4.6.5
Block Acquisition
To enable the program to run reliably on slower computers, results are not calculated each time a sample
is received. Instead, groups of samples are collected and added to an analysis buffer that is processed as
it becomes full. This processing delay is timed so that the display updates at least every 0.75 seconds.
4.7
Data Recording
The ADS1x31REF software can record incoming samples to a text file. This file can be loaded into other
programs for analysis. Data recording is performed using the controls in the Recording box.
Follow these steps to record data to a file:
Step 1.
Select or create a destination file. Either type the file path directly into the Destination file
control, or click the small open folder icon to the right of the control to open a dialog box from
which a file can be selected. If the selected file exists already, the program will display a
warning. Otherwise, type the name of the file that you wish to create.
Step 2.
Select a data format. Samples can be recorded as raw (decimal) codes or as volts. In both
cases, the data are written to the file as ASCII data, and the file is a text file.
Step 3.
Click the Record button. The program begins to collect and analyze data from the board, as
well as write it to the selected file. As recording proceeds, the recording time indicators are
updated.
Step 4.
Click Record again to stop the recording when the desired amount of data has been
collected.
The selected file is not opened or created until recording begins. If an error occurs at that time, recording
stops and a message displays in the status box.
17
SBAU175A
–
July 2010
–
Revised August 2011
ADS1131REF and ADS1231REF
Copyright
©
2010
–
2011, Texas Instruments Incorporated
