Question

A dual slope integrating type $A/D$ converter has $2\mu F$ capacitor and $100k\Omega$ resistor connected to it. If the reference voltage is taken as $7V$ and output voltage cannot exceed $15V$, the time for which reference voltage will be integrated is

• A. $212msec$
• B. $352msec$
• C. $150msec$
• D. $429msec$

Answer 1

The correct option is D $429msec$

Output voltage of dual slope $A/D$ converter
$V_0=\frac{1}{RC}{\int }_0^t{V}_{ref}dt$
$=\frac{1}{100\times {10}^3\times 2\times {10}^{-6}}{\int }_0^{t}7dt=5{\int }_0^{t}7dt=35t$

$\text{And output voltage}$, $V_0=15V,35t=15$
$t=\frac{15}{35}=0.429sec=429msec$