Accessories are included to convert the probes to 50 ohm single-ended.
For single ended it must be 50 ohm and for differential pairs 100 ohm. For PCB with controlled-impedance these are that common numbers. Differential Impedance: the impedance the difference signal sees. Tektronix baluns are an effective means for using single- ended test ...Learn More → Anyone that’s ever tried to put 75-ohm video onto a PCB stackup knows how high impedance will drive layer thicknesses.Most busses operate using 50-60 ohm impedance, which means you would typically use dielectric thicknesses of around 5 mils to achieve those impedances.
50 ohm single ended vs 100 ohm differential
But the long and short of it is that it is a compromise between low attenuation and power handling.But it became the standard impedance when designing for transmission line applications way back when.If a short section of a 50 ohm cable has a 75 ohm impedance, then 33% of the voltage signal will be reflected at each end of the 75-ohm section. About 11% of the signal will survive one round trip, 1.2% will survive two, and 0.15% survive three.In other words, the impedance of a single trace in the 100-ohm differential pair would be 65 ohms.