A digital voltmeter is required to measure a DC signal with superimposed AC noise. Which type of DVM is most likely to produce the most accurate reading?
Integrating type DVM because it averages the input over the conversion period
An integrating type DVM (for example, the dual-slope DVM) does not sample the input at one instant; it integrates the input voltage over a fixed conversion period and measures its average value.
Superimposed AC noise has an average of nearly zero over the integration period (and exactly zero if the period is a whole multiple of the noise or mains period), so the noise cancels out and only the DC component is read. This gives excellent noise rejection and high accuracy, which is why the dual-slope integrating DVM is the standard choice for noisy DC signals.
The feature named for the voltage-to-frequency DVM — needing long counting intervals for high accuracy — is a limitation on its speed, not a property that removes superimposed AC noise.
A ramp type DVM compares the input with a ramp at a single crossing instant, so a noise spike at that instant directly corrupts the reading.
A successive approximation DVM samples the input quickly over a short fixed time, so it captures the instantaneous noise along with the DC signal.
Hence, the answer is Integrating type DVM because it averages the input over the conversion period.
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Important Questions from Indicating Instruments
Hot wire ammeters are used for measuring
Which one of the following force is not needed for the satisfactory operation of any indicating (or measuring) instrument?
Assertion (A): Shunt of an ammeter has a low resistance
Reason (R): Shunt may be connected in series or in parallel with an ammeter.Which of the following statements are correct?
A. Ultrasonic method for liquid level measurement is not preferred in industrial applications.
B. In a pH meter, the glass electrode is the reference electrode.
C. A chromatograph is used for analyzing the composition of a gas.
D. The production of Korotkoff sounds in indirect blood pressure measurement is due to pressure pulses produced due to the difference in systolic and diastolic blood pressure.
Choose the correct answer from the options given below:
- Which instrument is representing an integrating type instrument?
