We all know why using a properly compensated 10:1 probe is a must when viewing MHz-speed signals on a scope with a 1 MOhm input impedance. Now who can supply a good use for a 1:1 probe? These probes have not found much use in my lab.
The only thing I can think of is that the 1:1 probes might be useful for making measurements of power supply ripple, switching artifacts, etc. I, however, question whether the 1:1 probe is readily capable of a connection with low-enough ground transfer impedance to really see what's going on in, for example, a switching power supply rail. Howard Johnson ("Healthy Power") and Jim Williams ("Minimizing Switching Regulator Residue in Linear Regulator Outputs", page 11) both discuss a similar technique but use plain coax instead of a 1:1 probe. In Howard Johnson's example, the coax shield is then soldered to the board with bus wire to achieve the lowest possible ground transfer impedance. Eliminating inductance in the ground wire is key to probing the fast switching artifacts. I'm not sure how well a 1:1 probe would do in this case, but it can probably be made to work okay.
Can anyone recommend any other uses for the 1:1 probe??
Best Answer
Noise in oscilloscope front ends is quite high, maybe 1mVp-p.
Using the 1:1 probe lowers the input-referred noise floor by an order of magnitude. Still pretty crappy, but opens a few doors.