The Histogram Analysis tool plots the histogram of the raw ADC conversion data for ADC1A, ADC1B, ADC3A, and ADC3B. This tool is useful for studying the statistical summary of the data set, mainly by computing the mean and standard deviation of the data from each channel. Noise degrades ADC resolution and the histogram tool can estimate an effective resolution, which is an indicator of the number of bits of ADC resolution losses resulting from noise generated by the various sources connected to the ADC when measuring a DC signal. The cumulative effect of noise coupling to the ADC output from sources such as the input drive circuits, the reference drive circuit, the ADC power supply, and the ADC is reflected in the standard deviation of the ADC output code histogram that is obtained by performing multiple conversions of a DC input applied to a given channel.

The histogram bin width is calculated using Scott's Rule by default. This method minimizes the mean-squared error in the bin approximation, assuming the data follows a Gaussian distribution. Alternatively, select Custom under the Binning Rule drop-down menu and enter the desired Codes per Bin setting in the field to the right.

Below the histogram plot is a Measurements summary table, which lists the Minimum, Maximum, Sigma, Peak-to-Peak, and Number of Bins for each channel. The histogram x-axis and the table statistics can be displayed in Codes or Voltage (V) by toggling the radio buttons under the Unit section to the right of the table.

Initiate data capture by specifying the number of samples and clicking the Capture button at the bottom of the Data Capture Configuration panel. Figure 6-7 shows an example data capture with all channels configured for an internal input short. ADC1A and ADC1B are configured for Gain = 4, and ADC3A and ADC3B are configured for Gain = 1.

Figure 6-7 Histogram Analysis Tool