How does an oscilloscope current probe work?
Current flow through a conductor causes an electromagnetic flux field to form around the conductor. Current probes are designed to sense the strength of this field and convert it to a corresponding voltage for measurement by an oscilloscope. This allows you to view and analyze current waveforms with an oscilloscope.
What is a probe in a circuit?
A current probe generates a voltage proportional to a current in the circuit being measured; as the proportionality constant is known, instruments that respond to voltage can be calibrated to indicate current. Current probes can be used both by measuring instruments and oscilloscopes.
How are current probes related to the source conductor?
Current probes are RF transformers that measure, or produce, a voltage in a 50-ohm load proportional to the current flowing through the probe window (i.e., its inner diameter, also called its aperture). Current probes are non-contact devices, in that they do not directly touch the source conductor or the line’s metallic surface.
How do you measure current in a circuit?
If the current measurement resistor were on the 0 V line, or if the circuit under test were fully floating compared to the oscilloscope, then this would be easy. Just take a standard voltage probe, connect its ground clip to one end of the resistor and its tip to the other side, and you would measure R × I.
Can a voltage probe be connected to a resistor?
Just take a standard voltage probe, connect its ground clip to one end of the resistor and its tip to the other side, and you would measure R × I. However, such a setup is impossible if the ground of the scope is connected to the ground of the board under test—either directly or indirectly.
What are the different types of current probes?
Editor’s Note: This article on current measurement and current probes is the third of a three-part series on probes and their proper use. Part 1, covered high-impedance passive probes. The second article discussed single-ended, differential, and high-voltage differential active probes. Part 3 will deal with current measurement and current probes.