ADC 0804 testing problem

Thread Starter


Joined Jun 8, 2012
Hello everyone!

I'm sorry for my bad english :). I have a few questions about a problem I can't solve.
I have created a program in Labview to calculate errors of 8 bit ADC 0804. Program is based on servo-loop method. The converter is in free running mode and the program is ploting all voltages from 0 to 255. Converter is working fine untill Vin reaches 4.4V (Code 220), after 4.4V converter doesnt work fine (I'm getting quite a big error) untill the program reaches code 255 (the last code is ploted properly). The image will make things more easy to understand (lower graph is error plot-plotting Vreal-Videal). Vcc is 5.12 V and I was thinking that the issue could be in fact that voltage measured on pin 9 is 1.48 and it should be 2.56 V.
Could anyone help me with this problem?
And my second question would be how to determine conversion time of this A/D converter?
Thank you!