Urgent:Digital AC/DC Test meter

[henry77]

Hello friends,

I have to design a test meter, which should measure DC voltage from 0-50v, and should measure input AC Signal (800hz to 500khz, upto -40dB). the output should be displayed on 3 1/2 digit LED Display.

for DC part of measurement i am planning to use ICL7107 which is ADC with LED driver IC , but i am confused for AC measurement. as i want dB level of signal to be displayed, sO plz guys help me out with your suggetions

thanx

 

[dougy83]

Have a look at the SSM2166 (mic amp with variable compression & noise gate) IC. Given an AC signal, it outputs a voltage (on AVG CAP) proportional to the logarithm of the rms value of the signal (plus an DC offset). You should be able to feed this voltage into your DC meter after appropriately scaling and shifting it.