The probe is where a measurement actually begins, and the wrong one can quietly ruin an otherwise perfect oscilloscope. A high bandwidth instrument connected through the wrong probe will show a rounded, attenuated, or simply wrong signal, without ever reporting an error. The short video below walks through what to look for when choosing one.
Passive probes: the default for most bench work
A standard «passive probe», typically with a 10x attenuation factor, is the default choice for most general purpose measurements. It reduces the loading the probe places on the circuit under test compared with a direct, unattenuated connection, at the cost of dividing the signal amplitude by ten, which the oscilloscope compensates for automatically once the probe is set correctly.
When a passive probe is not enough
A «differential probe» measures the voltage difference between two points, neither of which needs to be at ground potential, which is essential for floating or mains connected measurements, such as those covered in our article on measuring mains voltage. A «current probe» converts current into a proportional voltage without breaking the circuit. A «high voltage probe» extends the safe measurement range far beyond what a standard passive probe is rated for. Using the wrong category of probe for the job is one of the most common causes of a misleading, or genuinely unsafe, measurement.
Matching the probe to the oscilloscope
A probe's own bandwidth needs to meet or exceed the oscilloscope's bandwidth, or it becomes the actual limiting factor in the measurement, regardless of how capable the instrument itself is. The oscilloscope's manual will list the compensation range and connector type the instrument expects, which is the reference to check before selecting a probe for a new measurement.
ALLdata's role
ALLdata supplies passive, differential, current, and high voltage probes matched to its oscilloscope range, from general bench work to demanding power electronics and mains connected measurements.
Not sure which probe category your measurement needs? Talk to an ALLdata engineer, or browse our oscilloscope and probe range.