To detect and measure the electric current flowing through a conductor, an oscilloscope first needs to be connected to the signal source using a probe. The probe is a single-input device and its role is to be touched onto a circuit, to divert the electrical signal to the scope.
Oscilloscope probes must always first be safely grounded before use, using their included clip to connect to a common ground point on the circuit under test. It is good practice for ground leads to be as short as possible as this helps to keep the probe electrically ‘invisible’. This means a reduced impact on signal behaviour due to the probe or wire’s own inherent inductance, capacitance, and resistance characteristics, although there will always be some baseline influence to take into account. Invisibility, and thus minimal impact on the circuit under test, is one of the key goals to keep in mind when using current probes with an o-scope.
Various types of oscilloscope probes are available, with the ideal types for any given setup or scenario depending on various parameters - most importantly, the characteristics of the scope model being used, the type of devices or signal carriers it is being connected to, and the sorts of information about signals and waveforms being sought.
For improved performance and reliability of data, you should always use an appropriate probe tip and probe tip adapter for the equipment and application. When selecting an oscilloscope current probe, you should always ensure first and foremost that the probe’s input connector matches the connector type on the scope. Additionally, you will need to match the input resistance and capacitance of the scope and the probe in question. This is a critical factor in achieving proper signal transfer, and thus the accuracy of any data gathered.
Once a probe with a suitable capacitance has been identified, you can fine-tune the probe’s capacitance by adjusting its compensation network via its trimmer capacitor. This is known as compensating a probe and is usually done by twisting a recessed screw head near the tip of the probe, which in turn is connected to a built-in shunt capacitor.