Signal with Random Noise

Task: Two graphs will be plotted in Data Visualizer using a DC signal mixed with random noise.

A graph with 1-sample accumulation.
A graph with 64-sample accumulation.

Test setup: The random noise is generated using a device with DAC and added this random noise to the DC signal to be measured, as shown in Figure 1.

A signal with random noise is shown in Figure 1. The DC signal level is 740 mV and the noise amplitude is 640 mV pk-pk.

Figure 1. Signal with Random Noise Oscilloscope Capture

1. A graph with 1-sample accumulation:

In the example code, the configuration of macro definitions is as below:

#define HARMONIC_NOISE  0
#define ADC_64X_ACCUMULATOR_ENABLE   0
#define SAMPLING_DELAY 0
#define ENABLE_ASDV  0

After downloading the code with the above macro definitions, the Data Visualizer graph is as shown in Figure 2:

Figure 2. Signal with Random Noise: 1-Sample Accumulation

ADC count can be seen varying from 200 to 400 because of random noise. That means ADC count is varying ±100 counts (400 to 200 → 300 ±100 counts).

2. A graph with 64-sample accumulation:

In the example code, the configuration of macro definitions is as below:

#define HARMONIC_NOISE  0
#define ADC_64X_ACCUMULATOR_ENABLE   1
#define ENABLE_SMP_DLY 0
#define ENABLE_AUTOTMATIC_SAMP_DLY  0

After downloading the code with the above macro definitions, the Data Visualizer graph is as shown in Figure 3:

Figure 3. Signal with Random Noise: 64-Sample Accumulation

From the graph, it can be observed that by oversampling with 64 ADC samples accumulation, the ADC result count range has been reduced. If the signal is zoomed, the image is as shown in Figure 4:

Figure 4. Zoomed Signal with Random Noise: 64-Sample Accumulation

The ADC result count range is varying between 295 to 270. That means ADC count is varying ±13 counts (295 to 270 → 282 ±13 counts).