ADC 0804 testing problem

Discussion in 'The Projects Forum' started by Vex89, Jun 8, 2012.

  1. Vex89

    Thread Starter New Member

    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!