Author Topic: Size (5mm, 3.5mm, 2.5mm...) of passive probes and price  (Read 273 times)

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Offline LaurentR

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Size (5mm, 3.5mm, 2.5mm...) of passive probes and price
« on: July 13, 2018, 04:43:24 pm »
I keep being surprised by the default 5mm probes shipped with modern scopes (most recently for me the ZP03 of the RTB2k). They are all very bulky, heavy and even for the simplest work (probing 0.1" headers), they don't stack well (clips) and exert substantial mechanical force due to their weight. The cheap ones are a pain to position due to their stiff cable. I am having a hard time understanding why standard probes (5mm) are so big?

OTOH, I got my hands on (more expensive) 3.5mm Caltest CT3290RA probes (equivalent Tek P6139A) and while their assembly is a bit unusual (clips...), they are small and light and overall just easier to use in all conditions than 5mm probes (they also have a very complete accessory pack available).

So my questions to everybody:
* Is the bigger size of the default 5mm probes better for anything?
* Are they the default probes for new scopes just because they are cheaper to make?
* Are they any really nice 5mm probes (better at a price point than 3.5mm or 2.5mm ones)?
* Are there any fundamental electrical reasons why 3.5mm or 2.5mm probes are (much) more expensive? I assume it's at the point where manufacturing smaller probes is more expensive, but is there anything electrically more complex (coax size, impedance matching...)?

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