Question

A 200 mV full scale dual-slope $3\frac{1}{2}$ digit DMM has a reference voltage of 100 mV and a first integration time of 100 ms. For an input of $[100+10cos(100\pi t\left)\right]mV,$ the conversion time (without taking the auto-zero phase time into consideration) in millisecond is

• A. 200

Answer 1

The correct option is A 200
In dual slope converter total conversion time

T = 1st integration period + 2nd integration period

$=T_1+T_2$

$=100msec+T_2$

$Toobtain{T}_{2}wecanuse{V}_{in}{T}_1=V_{ref}{T}_2$

$\Rightarrow 100mV\times 100msec=100mV\times T_2$

$\Rightarrow T_2=100msec$

$\Rightarrow T=100+100=200msec.$