Power rail probes (like Tektronix TPR1000) have very low input impedance (50 ohm) and high offset capability for measuring millivolt ripple on DC power rails without loading the supply or missing fast transients.
// Specifications
Standard
Tektronix TPR or similar
Impedance
50 ohm to minimize loading
Offset
Up to plus/minus 60V DC offset
Bandwidth
1 GHz typical
Noise Floor
Less than 500 uV RMS
Use Case
PDN power integrity DC-DC converter ripple measurement