CRO probes, Opinions - best place to buy ?

"kreed"




** Farnell in One have these low cost 250 MHz, 10:1 probes.

http://au.farnell.com/jsp/endecaSearch/partDetail.jsp?SKU42%84069

http://au.farnell.com/jsp/endecaSearch/partDetail.jsp?SKU34%21624

http://au.farnell.com/jsp/endecaSearch/partDetail.jsp?SKU84%71738


Might be better made and last longer -  might not.


BTW:

The whole business of CRO probe bandwidth ratings is quite deceitful & full
of traps for the unwary.

Eg:

The quoted 250 MHz figure only applies to the 10:1 position  -  it is very
much lower at 1:1.

The source impedance must be 50 ohms to achieve the claimed bandwidth.

The probe has around 15 pF capacitance  =  42 ohms at 250 MHz  !!

Darn long way from 10 Mohms  -  what   ???


For most RF and wide band measurements, it is far better to use some 50 or
75 ohm coax and a matching terminator at the CRO end of the cable.

Then the load impedance is a fixed,  known value and bandwidth is limited
only by the CRO itself   -   NOT  by cable reflections and standing wave
impedance nulls.





.......   Phil

That's a pretty good price for a 250MHz probe.
Buy one and try it. I've found the "cheapie" high bandwidth probes to
be pretty good in general.

Make sure it comes with the accessory pack with the high speed ground
pin attachment, essential for high bandwidth work.

Dave :)