I can understand that the idea of probe compensation is to make the sensed signal to be frequency independent as shown below 9C * R = R * 9C:

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Does that mean that probe compensation should be done only in 10X setting? And what happens if the probe is only used at 1X setting? In that case we cannot rely on the waveform seen on scope as much ass in 10X case?

  • \$\begingroup\$ Examine what happens when the probe is switched to the X1 position. The two components in series with the signal are shorted, with the input signal now applied directly to the scope input. Now think about what happens or does not happen if you vary the value of (9C). \$\endgroup\$ – Dwayne Reid Dec 3 '18 at 5:14
  • \$\begingroup\$ I see, if it is like that then nothing happens. It is useless to try to compensate correct? \$\endgroup\$ – cm64 Dec 3 '18 at 9:50
  • \$\begingroup\$ This also brings this question: If the probe compensation is possible only when the scope probe is set for 10X, why then why to use 1X setting at all? In what circumstances 1X is superior to 10X setting? \$\endgroup\$ – cm64 Dec 3 '18 at 9:59
  • \$\begingroup\$ As to why use x1, compare noise floor in volts for each on a real oscilloscope. \$\endgroup\$ – Spehro Pefhany Dec 3 '18 at 12:37
  • \$\begingroup\$ So is the compensation possible or not at 1X? The answer below says it is possible but the comment above indicates it is not possible \$\endgroup\$ – cm64 Dec 4 '18 at 20:16

No, you can compensate probes with any attenuation ratio.

The goal of probe compensation is to impedance match the probe to the scope. So, the waveform on screen is really the only indicator you have of a match.

Take a look at Table 2 in the Quick Start Guide for this switchable 10:1/1:1 probe: https://literature.cdn.keysight.com/litweb/pdf/N2140-92002.pdf

There's a different input capacitance in 10:1 mode (100pf) and 1:1 mode (15pf). However, the compensation range is independent of the attenuation setting (15-30pf).

Probe compensation is something you can always consider. Very high end probes even ship with S-parameter data that gets auto-loaded into the scope for correction.

It's also worth noting that 1:1 probes give you lower bandwidth and higher loading.

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