Instrumentation & Measurements: Match Device to Application List I A. Digital counter B. Schering bridge C. Megger D. Spectrum analyser List II Measurement of harmonics (spectral components) Measurement of frequency Measurement of loss angle of dielectric Measurement of insulation resistance
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AA-1, B-2, C-3, D-4
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BA-4, B-3, C-2, D-1
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CA-2, B-3, C-4, D-1
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DA-4, B-1, C-3, D-2
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EA-2, B-4, C-3, D-1
Answer
Correct Answer: A-2, B-3, C-4, D-1
Explanation
Introduction / Context:This question matches classic instruments to what they measure, spanning frequency counting, dielectric testing, insulation-resistance measurement, and spectral analysis. Mastery of these pairings aids in selecting the right tool for RF, power, and materials labs.
Given Data / Assumptions:
- Digital counter measures repetitive events to compute frequency.
- Schering bridge evaluates capacitors and dielectrics, yielding loss angle (dissipation factor).
- Megger (insulation tester) applies high DC voltage to measure very high resistances.
- Spectrum analyser displays amplitude versus frequency, revealing harmonics and spurs.
Concept / Approach:
Use each instrument’s defining capability: counters time zero-crossings/pulses, bridges compare impedances to extract dielectric loss, meggers characterize insulation via megohm-scale resistance, and spectrum analysers resolve frequency-domain content including harmonics and intermodulation products.
Step-by-Step Solution:
A (Digital counter) → frequency measurement by counting cycles over a gate time ⇒ 2.B (Schering bridge) → measures dielectric loss angle/tan δ in capacitors/insulators ⇒ 3.C (Megger) → measures insulation resistance at elevated DC voltage ⇒ 4.D (Spectrum analyser) → reveals harmonic content and spectral lines ⇒ 1.Verification / Alternative check:
Typical lab procedures: frequency counter on a known RF source; Schering bridge datasheets emphasize tan δ; meggers specify ranges in MΩ to GΩ; spectrum analysers display multi-tone spectra showing harmonics clearly.
Why Other Options Are Wrong:
Assigning the megger to “harmonics” or the counter to “loss angle” ignores instrument physics. The Schering bridge targets dielectric characterization, not frequency counting.
Common Pitfalls:
Confusing an oscilloscope (time-domain) with a spectrum analyser (frequency-domain); using a multimeter for insulation tests where a megger is appropriate due to higher test voltage.
Final Answer:
A-2, B-3, C-4, D-1