Full Wave Rectifier Type Instrument

Q.

The maximum peak to peak voltage of an AM wire is$24mV$ and the minimum peak to peak voltage is$8mV$. The modulation factor is

1. $10\%$

2. $20\%$

3. $25\%$

4. $50\%$

Q. A half wave rectifier type AC voltmeter consists of a series resistance $R_s$, ideal diode and PMMC instrument as shown in figure. The internal resistance of instrument is $100\Omega$ and full scale deflection is produced by a DC current of 10 mA. The value of $R_s$ required to obtain full scale deflection with an AC voltage of 100 V (rms), applied to the input terminal is _______ $\Omega$.

1. 44
2. 4400
3. 440
4. 401

Q. An ac voltmeter uses the circuit shown below, where the PMMC meter has an internal resistance of $100\Omega$ and requires a dc current of 1 mA for full scale deflection.
Assuming the diodes to be ideal, the value of $R_s$ to obtain full scale deflection with 100 V (ac rms) applied to the input terminal would be

1. $80k\Omega$
2. $89k\Omega$
3. $89.9k\Omega$
4. $90k\Omega$

Q. An electronic voltmeter consisting of a full wave precision rectifier and an average circuit gives correct R.M.S value for square wave inputs. It's reading for a 2 V peak to peak sinusoidal input will be

1. $\frac{2}{\pi }V$
2. $\frac{1}{\pi }V$
3. $\frac{2}{\sqrt{2\pi }}V$
4. $\frac{\sqrt{2}}{\pi }V$

Q. The scale of a full wave rectifier type average sensing meter is calibrated to read the r.m.s value for ideal sine wave signal (form factor 1.11). Determine the multiplying factor of the meter if it is used to measure the r.m.s value of square waves.

1. 1.11
2. 1/1.11
3. 1.0
4. depend on the frequency of the square wave