Difference: ADCAndDAC (6 vs. 7)

Revision 72020-08-07 - UliRaich

Line: 1 to 1

META TOPICPARENT	name="Exercises"

Exercise 9: Analogue to Digital (ADC) and Digital to Analogue (DAC) conversion

Introduction

Line: 18 to 18

Checking linearity

If we connect the DAC output to the input of an ADC channel and we slowly ramp up the DAC value from 0 to its maximum and we read back the signal level with the ADC, then we expect a perfectly linear curve. This is true under the condition that both, the DAC and the ADC are perfectly linear.

Changed:

<
<

linearity full range	linearity restricted range

>
>

Linearity curve expected	Linearity curve measured

As we can see, the curve becomes very non-linear for values above 200 (3.3V * 200 / 256 ~ 2.6 V). Unfortunately we do not know if the ADC or the DAC is responsible for this non-linearity. We need an external ADC to check. We also see that the line does not pass though 0,0 as it should.

Verifying linearity with an external ADS1115

Line: 45 to 45

Here is a graph when fitting a polynomial of grade 5

Changed:

<
<

>
>

Line: 81 to 81

<--/commentPlugin-->

Deleted:

<
<

META FILEATTACHMENT	attachment="linearity.png" attr="" comment="" date="1596111249" name="linearity.png" path="linearity.png" size="32384" user="UliRaich" version="1"

META FILEATTACHMENT	attachment="restrictedLinearity.png" attr="" comment="" date="1596111254" name="restrictedLinearity.png" path="restrictedLinearity.png" size="29920" user="UliRaich" version="1"
META FILEATTACHMENT	attachment="linADS1115.png" attr="" comment="" date="1596115847" name="linADS1115.png" path="linADS1115.png" size="30931" user="UliRaich" version="1"

Changed:

<
<

META FILEATTACHMENT	attachment="polynomial.png" attr="" comment="" date="1596180154" name="polynomial.png" path="polynomial.png" size="3560" user="UliRaich" version="1"

>
>

META FILEATTACHMENT	attachment="polynomial.png" attr="" comment="" date="1596810201" name="polynomial.png" path="polynomial.png" size="2360" user="UliRaich" version="2"

META FILEATTACHMENT	attachment="fit.png" attr="" comment="" date="1596180450" name="fit.png" path="fit.png" size="32457" user="UliRaich" version="1"
META FILEATTACHMENT	attachment="corrected.png" attr="" comment="" date="1596181140" name="corrected.png" path="corrected.png" size="38453" user="UliRaich" version="1"
META FILEATTACHMENT	attachment="openhantek.png" attr="" comment="" date="1596206560" name="openhantek.png" path="openhantek.png" size="95945" user="UliRaich" version="1"

Added:

>
>

META FILEATTACHMENT	attachment="expected.png" attr="" comment="" date="1596808397" name="expected.png" path="expected.png" size="34510" user="UliRaich" version="1"
META FILEATTACHMENT	attachment="polynomialv2.png" attr="" comment="" date="1596810306" name="polynomialv2.png" path="polynomialv2.png" size="2360" user="UliRaich" version="1"
META FILEATTACHMENT	attachment="linearity.png" attr="" comment="" date="1596811295" name="linearity.png" path="linearity.png" size="35217" user="UliRaich" version="1"

View topic | History: r10 < r9 < r8 < r7 | More topic actions...