Question

In a dual slop integrating type digital voltmeter, the first integrating is carried out for 10 periods of the supply frequency of 50 Hz. If the reference voltage used is 2 V, the total conversion time for an input of 1 V is _________

(a) 0.01 s

(b) 0.05 s

(c) 0.1 s

(d) 1 s

I had been asked this question in an internship interview.

This question is from Calculation of I(0+), di/dt(0+), d2I/dt2(0+) in Circuits Involving both Capacitor and Inductor in portion Application of the Laplace Transform in Circuit Analysis of Network Theory

Answer 1

Correct choice is (c) 0.1 s

The explanation: In a dual slope integrating digital voltmeter,

\((\frac{t_1}{t_2})\) Vin = Vref

Where, t1 = first integration time = 10 × \(\frac{1}{50}\) = 0.25

But Vin = 1 V and Vref = 2 V

∴ t2 = \(\frac{V_{in} t_1}{V_{ref}}\) = 0.1 s.