OK, then the measurement itself has bigger errors near zero and not necessarily the ADC of the ESP82266 should be incriminated for the poor result. Fluke87 on 4V DC scale has a resolution of 0.001V and an accuracy of 0.1% of reading + 1 digit, see page 36 here: https://physics.ucsd.edu/neurophysics/Manuals/Fluke/87______umeng0800 If you want an accurate graph error, you need to use all digits and estimate the overall measurement error of your measuring device too. good luck, Vasile On Thu, Oct 22, 2015 at 1:38 AM, Justin Richards wrote: > "V Actual" was the data in the left column. It was the voltage that was > set using the Fluke. I should have perhaps used more digits to indicate > precision. > "V ADC" the data in the right column was then read from the ESP8266. I ha= d > it set to print the ADC every second. The value jumped around a little so= I > tried to average the value. > On 22/10/2015 1:00 AM, "embedded systems" wrote: > > > Justin, > > just one remark about the measurement accuracy. > > > > "V Actual" should be the value of the calibrated measurement device (th= e > > standard) while "V ADC" the value to be measured. > > The standard should be better represented than measured value as number > of > > digits and accuracy. > > In your measurement V ADC is not the left column and Fluke value the > right > > one? > > > > > > On Tue, Oct 20, 2015 at 5:15 AM, Justin Richards < > > justin.richards@gmail.com> > > wrote: > > > > > I decided to measure and plot the error of the ESP8266 internal ADC. > > > > > > Thought I would share the results. > > > > > > PSU HP E3631A and Fluke 87 to set the voltage between 0 and 1.020 > Volts. > > > > > > V Actual,V ADC > > > 0.01,0.001 > > > 0.02,0.008 > > > 0.03,0.017 > > > 0.04,0.028 > > > 0.05,0.038 > > > 0.06,0.05 > > > 0.07,0.06 > > > 0.08,0.07 > > > 0.09,0.08 > > > 0.1,0.09 > > > 0.11,0.102 > > > 0.12,0.113 > > > 0.13,0.124 > > > 0.14,0.136 > > > 0.15,0.149 > > > 0.16,0.158 > > > 0.17,0.168 > > > 0.18,0.18 > > > 0.19,0.189 > > > 0.2,0.2 > > > 0.21,0.209 > > > 0.22,0.221 > > > 0.23,0.232 > > > 0.24,0.242 > > > 0.25,0.253 > > > 0.26,0.266 > > > 0.27,0.275 > > > 0.28,0.285 > > > 0.29,0.297 > > > 0.3,0.306 > > > 0.31,0.316 > > > 0.32,0.326 > > > 0.33,0.338 > > > 0.34,0.35 > > > 0.35,0.356 > > > 0.36,0.367 > > > 0.37,0.38 > > > 0.38,0.394 > > > 0.39,0.404 > > > 0.4,0.412 > > > 0.41,0.425 > > > 0.42,0.438 > > > 0.43,0.447 > > > 0.44,0.458 > > > 0.45,0.466 > > > 0.46,0.477 > > > 0.47,0.488 > > > 0.48,0.496 > > > 0.49,0.508 > > > 0.5,0.518 > > > 0.51,0.53 > > > 0.52,0.54 > > > 0.53,0.552 > > > 0.54,0.562 > > > 0.55,0.573 > > > 0.56,0.582 > > > 0.57,0.593 > > > 0.58,0.603 > > > 0.59,0.613 > > > 0.6,0.625 > > > 0.61,0.635 > > > 0.62,0.649 > > > 0.63,0.66 > > > 0.64,0.669 > > > 0.65,0.678 > > > 0.66,0.693 > > > 0.67,0.701 > > > 0.68,0.711 > > > 0.69,0.722 > > > 0.7,0.731 > > > 0.71,0.744 > > > 0.72,0.753 > > > 0.73,0.763 > > > 0.74,0.776 > > > 0.75,0.785 > > > 0.76,0.795 > > > 0.77,0.81 > > > 0.78,0.816 > > > 0.79,0.829 > > > 0.8,0.835 > > > 0.81,0.847 > > > 0.82,0.857 > > > 0.83,0.868 > > > 0.84,0.878 > > > 0.85,0.891 > > > 0.86,0.901 > > > 0.87,0.914 > > > 0.88,0.925 > > > 0.89,0.936 > > > 0.9,0.945 > > > 0.91,0.957 > > > 0.92,0.965 > > > 0.93,0.977 > > > 0.94,0.986 > > > 0.95,0.998 > > > 0.96,1.006 > > > 0.97,1.018 > > > 0.98,1.024 > > > 0.99,1.024 > > > 1,1.024 > > > 1.01,1.024 > > > 1.02,1.024 > > > > > > -- > > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > > > View/change your membership options at > > > http://mailman.mit.edu/mailman/listinfo/piclist > > > > > > > > -- > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > > View/change your membership options at > > http://mailman.mit.edu/mailman/listinfo/piclist > > > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .