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Electrical Measurements online test on “Voltage to Frequency Converter Type Integrating DVM”.
1. In a voltage to frequency converter type integrated DVM _____________
a) voltage is converted to time
b) voltage is converted to frequency
c) frequency is converted to voltage
d) frequency is converted to time
Answer: a
Clarification: We know that the quantities time and frequency are related to each other. Voltage is converted into time in a voltage to frequency converter type integrating DVM.
2. Input voltage is measured by ____________
a) using a voltmeter
b) counting pulses
c) using a multimeter
d) using an ammeter
Answer: b
Clarification: A pulse train is generated. Their frequency depends on the frequency of the unknown voltage. Number of pulses present in a definite interval are counted. Unknown input voltage is a measure of the pulses generated.
3. What is the main component of an integrating type DVM?
a) diode
b) amplifier
c) op amp
d) oscillator
Answer: c
Clarification: An op amp forms the heart of the integrating type DVM. Op amp is used as an integrator. The input signal is integrated for a fixed interval giving rise to a ramp signal at the output.
4. When input is positive, then output is?
a) growing exponential signal
b) decaying exponential signal
c) positive going ramp
d) negative going ramp
Answer: d
Clarification: The op amp produces a negative going ramp signal for a positive input voltage. Capacitor is discharged after some time and the output returns to zero. The next cycle starts and the output is a sawtooth waveform. Figure shows the output sawtooth waveform.
5. What is the effect of the input signal on the output teeth?
a) directly proportional
b) inversely proportional
c) independent
d) square proportional
Answer: a
Clarification: When the input signal in a voltage to frequency conversion type integrated DVM is doubled, the number of tooth in the output signal is doubled per unit time. This doubles the frequency of the output signal.
6. Sawtooth pulses enter into a reversible counter.
a) True
b) False
Answer: a
Clarification: The sawtooth output signal obtained from the integrating type DVM is passed through a reversible counter. A digital readout displays the value measured by the reversible counter.
7. Application of an input voltage generates a ____________
a) linear signal at the output
b) ramp at the output
c) exponential signal at the output
d) unit step signal at the output
Answer: b
Clarification: When an input voltage of magnitude Vin is applied at the input, capacitor C is charged by the charging current Vin/R1. As a result a ramp signal is produced at the output.
8. Number of pulses is related to frequency.
a) True
b) False
Answer: a
Clarification: Each tooth in the sawtooth waveform produces a pulse at the output of the pulse generator. Hence the number of tooth i.e. the frequency is directly related to the number of pulses.
9. Accuracy depends on ____________
a) input voltage
b) drop across the capacitor
c) magnitude and stability of pulse generator
d) magnitude of the ramp
Answer: c
Clarification: Accuracy of the voltage to frequency conversion depends on the capacity of the pulse generator to produce an electric charge with a suitable magnitude and stability. Hence the accuracy depends on the precision of the charge feedback.
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