Electrical Measuring Instruments: Connections, Design, and Resistance Measurement

All flashcards

What does an ammeter measure, and how is it connected?

An ammeter measures current through a component or branch. It is connected in series so that the same current passes through the meter and the measured part.

Why should an ammeter have very low resistance?

A series ammeter adds resistance to the branch. Keeping that resistance very low minimizes the change it causes to the current being measured.

What does a voltmeter measure, and how is it connected?

A voltmeter measures potential difference between two points. It is connected in parallel across the component because parallel elements share the same potential difference.

Why should a voltmeter have very high resistance?

High resistance limits the current drawn by the voltmeter, helping it measure a component’s potential difference without significantly disturbing the circuit.

What is meter loading?

Meter loading is the change a measuring instrument causes to the circuit being measured. For example, an ammeter’s series resistance can reduce current, while a voltmeter with insufficient resistance can draw noticeable current.

Quiz questions

1. What does a digital meter's analog-to-digital converter do?Answer: Converts an analog electrical measurement into a digital representation.
2. A digital ohmmeter supplies a known constant current through a component. What does it measure to determine resistance?Answer: The voltage across the component.
3. Why should a component be isolated from other circuit paths when measuring its resistance?Answer: Other paths could contribute to the measured equivalent resistance.
4. Why must an ohmmeter not be connected to a live circuit?Answer: External voltage can damage the meter and invalidate the measurement.
5. What produces the pointer movement in a traditional analog meter?Answer: Current in a coil creates a magnetic effect that turns the pointer.