Hi Jerry,
What I meant is that you probably used a more sensitive V/div for the probes. In theory it could be, for instance, that you used 0.5 V/div for the normalizer and 0.1 V/div for the probe, while the plugins have different input C at 0.5 V/div but equal input C at 0.1 V/div.
For the present purpose I would call the calibrator output low ohmic. Though "officially" a 50R source, cable and 50R feedthru should be used.
I saw now that I made a severe mistake in the overshoot calculation. I completely forgot that the probe has an internal C in parallel with the amplifier input C. That considerably reduces the probe mismatch effect (and explains why your P6105 can have 13 pF input C but still can be adjusted for 22 pF amplifier C).
For the 7A22 I bought a pair of P6062B. I also have a pair of differential probes P6023 but these are so large.
Albert
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Hi Albert,
The amplifiers were all three set for a good display on all test. The calibrator output of a 7834 was used, it is a high impedance source. I agree that the main duty of a normalizer to to get as many probes and amplifiers working together as possible.
My P6105 100mhz probe from Tek is marked for 13pf but can be set for use with a 22pf amplifier. Very few probes can be adjusted to 47pf input required for a stock 7A22. I am not sure what range the 7A22 can be used with.
Pomona boxes are nice and shielded but I doubt that shielding is necessary in a typical lab or shop setting. They are pricy. I use a $1.90 plastic box from allelectronics.
Jerry Massengale
Hi Jerry,
I could be wrong but calculations say that the step response overshoot (or undershoot) of the transfered probe should be about twice that of the transfered normalizer. For instance, if both are correctly adjusted for 20 pF 'scope input and then moved to 18 pF 'scope input, the probe would show about 10% overshoot and the normalizer about 5%.
Did you use the same V/div settings for probe and normalizer? Did you use a low impedance source for testing?
Albert
