2.1 Measuring Instruments

• Meaning and importance of measuring electrical quantities
• Coil-based (moving-coil) measuring instruments and their principle of operation
• Analogue and digital instruments and how to select a suitable one
• Converting a galvanometer into an ammeter using a shunt
• Converting a galvanometer into a voltmeter using a multiplier
• Computing shunt and multiplier resistance for a given range
• Zeroing, range selection and adjusting the pointer
• Using coil-based and digital meters and comparing their accuracy
• Error correction and the calibration of measuring instruments
• Safe handling, storage and care of measuring instruments

• explain the principle of operation of coil-based measuring instruments
• convert coil-based instruments to measure voltage and current
• select a suitable instrument for measuring a specified electrical quantity
• perform error correction procedure on coil-based measuring instruments
• use coil-based and digital meters to measure electrical quantities
• recognise the importance of electrical measuring instruments

“How do measuring instruments work?”

“How are measuring instruments calibrated?”

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1. Measuring electrical quantities
   40 min · 1 practice tasks · quiz
   Introduce electrical measuring instruments and explain why accurate measurement matters.
2. Principle of operation of coil-based instruments
   40 min · 1 practice tasks · quiz
   Explain how a moving-coil instrument works.
3. Analogue and digital meters
   40 min · 1 practice tasks · quiz
   Compare analogue coil-based meters with digital meters and select a suitable instrument.
4. Converting a galvanometer to an ammeter and a voltmeter
   40 min · 1 practice tasks · quiz
   Explain how a galvanometer is converted using a shunt and a multiplier.
5. The shunt and extending the ammeter range
   40 min · 1 practice tasks · quiz
   Calculate the shunt resistance needed to extend the range of an ammeter.
6. The multiplier and extending the voltmeter range
   40 min · 1 practice tasks · quiz
   Calculate the multiplier resistance needed to extend the range of a voltmeter.
7. Zeroing and range selection
   40 min · 1 practice tasks · quiz
   Set the pointer to zero and select a suitable range before measuring.
8. Using analogue and digital meters
   40 min · 1 practice tasks · quiz
   Measure electrical quantities with analogue and digital meters and compare their accuracy.
9. Error correction and calibration
   40 min · 1 practice tasks · quiz
   Identify sources of error and correct readings by calibration.
10. Safe handling, storage and importance
    40 min · 1 practice tasks · quiz
    Handle and store measuring instruments safely and appreciate their importance.