BeginnerTopic 25 of 106Electrical Engineering
Measuring instruments
Multimeters and oscilloscopes measure voltage, current, resistance and waveforms.
In depth
Multimeters measure V, I and R; oscilloscopes show waveforms; LCR meters measure components; clamp meters sense current via magnetic field; insulation testers find leakage. Accuracy, range and safety category (CAT) matter.
Key points
- Ammeter in series, voltmeter in parallel
- True-RMS for non-sinusoids
- Probe bandwidth and loading
ExampleAn oscilloscope reveals ripple that a multimeter averages away.
What is Measuring instruments?
Multimeters and oscilloscopes measure voltage, current, resistance and waveforms.
Why is it important to understand measuring instruments?
Measuring instruments let you check a design against reality, which is the fastest way to find faults on a bench or in the field.
How do I measure current safely?
Put the meter in series with the circuit, set the correct range, and never connect an ammeter directly across a voltage source.
Why does a scope probe need compensation?
The probe's capacitance must match the scope input, otherwise the waveform looks distorted, especially on fast edges.
How is Measuring instruments used in practice?
Typical applications include measuring the voltage at a sensor to find a broken connection, capturing the waveform of a switching converter on an oscilloscope and checking the resistance of a cable for continuity.
What should I learn before Measuring instruments?
Study "Fuses and circuit breakers" first (topic 24 of 106 in Electrical Engineering). It covers the groundwork this topic builds on.
What are the key points of Measuring instruments?
Ammeter in series, voltmeter in parallel. True-RMS for non-sinusoids. Probe bandwidth and loading.
Can you give an example of Measuring instruments?
An oscilloscope reveals ripple that a multimeter averages away.
What comes after Measuring instruments?
The next topic is "Node-voltage analysis", which builds directly on this one.
How difficult is Measuring instruments?
It is classed as Beginner in Electrical Engineering (topic 25 of 106). It is an entry-level topic. It relies only on basic school mathematics and the ideas introduced earlier in this discipline.