Cheap 10X inline BNC attenuator? - Page 1
Forum section: electronics / testgear

author: Plasmateur
author_rank: Regular Contributor
timestamp: September 03, 2017, 02:24:05 am
content: Here are two examples of what I am looking forThe exact versionhttp://www.testpath.com/Items/Attenuator-BNC-50-Ohm-2W-2GHz-10X-117-010.htmThe cable versionhttp://probemaster.com/6143-bnc-to-bnc-10x-attenuation-cable/I believe this is just a 9M Ohm resistor and a few capacitors to make up the inner workings of a 10X probe.I don't need the bandwidth of the tektronix option. Something on the order of 200MHz would be nice.Are these common? I'm having a rough time finding any other options online.

author: Plasmateur
author_rank: Regular Contributor
timestamp: September 03, 2017, 02:50:33 am
content: Let's say both out of curiosity.For the 50Ohm solution.I could use a 20dB attenuator to give me 10X less voltage. But would that functionally be a high impedance measurement? If not. That will not work.For the 1MOhm solution ( I would need this for my Rigol DS1054z) ....if I use a T adapter terminated at 50Ohms, while the other side had a 20dB attenuator, I believe I have the same situation as above. In which case, if that is not seen as a high impedance to the DUT, that will now work.In which case. I need the 1M solution.

author: tautech
author_rank: Super Contributor
timestamp: September 03, 2017, 03:42:25 am
content: Look here:https://www.eevblog.com/forum/buysellwanted/fs-us-misc-tek-parts-and-fairchild-voltage-regulator/

author: Plasmateur
author_rank: Regular Contributor
timestamp: September 03, 2017, 05:29:42 am
content: Quote from: blueskull on September 03, 2017, 04:03:00 amAhhh, Just as I had suspected however I need the source to see 10M of impedance....or higher.The 1.125M resistor you are suggesting. That's not something that is normally on a 10X probe is it?http://www.radio-electronics.com/info/t_and_m/oscilloscope/oscilloscope-probes.phpIt appears that whatever is being measured by that 10X probe is seeing 10M of impedance.If something like this isn't available as a BNC inline feed through, I might just have to make it.

author: ADT123
author_rank: Regular Contributor
timestamp: September 03, 2017, 05:48:55 am
content: As other have said to do this at 50 ohm is easy but if you want to keep high impedance and high bandwidth your options are more limited. It would be useful to know why you are doing this, if it is to get a higher input voltage for your scope be very careful - consider a differential scope probe instead.One option would be just to use a 10:1 scope probe - most come with an adaptor to connect the input back to BNC. A bit of a messy solution but at least it can be trimmed to give the correct response on your scope.Another option would be the following but it only has a 20MHz bandwidth.https://www.picoauto.com/products/test-leads/101-attenuator

author: Plasmateur
author_rank: Regular Contributor
timestamp: September 03, 2017, 05:56:00 am
content: Quote from: ADT123 on September 03, 2017, 05:48:55 amEase of design for a particular diagnostic I am attempting to make.And the measurement environment is saturated with RF, so using an ordinary 10X probe with an exposed tip might be more susceptible to RF pickup.

author: Plasmateur
author_rank: Regular Contributor
timestamp: September 03, 2017, 06:05:08 am
content: Quote from: blueskull on September 03, 2017, 05:33:45 amForgive me, perhaps I'm mixing up the terminology based on what I found here:https://electronics.stackexchange.com/questions/38240/is-there-a-10x-probe-compensator-bnc-but-with-out-the-probeFor a similar question, the last poster called it a "BNC feed through attenuator"From what I think you're telling me, an attenuator and a 10X probe are two different animals.The source of the 10X probe tip sees 10M (which is what I need)The source of the attenuator opposite of the oscope's 1M termination sees 1M.

author: markb82
author_rank: Regular Contributor
timestamp: September 03, 2017, 07:49:36 am
content: How about a probe tip to BNC adapter like HP 10218a (http://4gte.com/hp-agilent-10218a-probe-tip-to-bnc-adapter-for-10020a-10218-60001-new.html).Then just use a regular 10x probe and you have 10meg input with a BNC.$20 on eBay with free shipping. Doesn't get any easier than that :http://www.ebay.ca/itm/HP-10218A-Probe-Tip-Adapter-NOS-Unused-HP-8405A-8508A-Vector-Voltmtr-Agilent-/263181836710?hash=item3d46dc21a6:g:-FYAAOSwNm5ZqhCJ

author: alm
author_rank: Super Contributor
timestamp: September 03, 2017, 08:06:56 am
content: A 10x probe with probe tip to BNC adapter should provide a fully coaxial connection and would probably be the most common and hencr cheapest. If your probe did not come with one, make sure the one you're buying fits your probe tip. Probe tips are not standardized.The alternative might be to build your own in a diecast Pomona box. Making one with a flat response up to 200 MHz may not be trivial. It would definitely have to be compensated like a probe, and the cable impedance will be an issue.

author: tggzzz
author_rank: Super Contributor
timestamp: September 03, 2017, 08:09:10 am
content: Quote from: Plasmateur on September 03, 2017, 05:29:42 amDon't forget that a 10Mohm *10 probe is only 10Mohm at low frequencies - you have to take the tip capacitance (typically 15pF) into account.If you are working at 200MHz, a "low impedance" "Z0" "resistive divider" probe will have a significantlyhigherimpedanceFFI, seehttps://entertaininghacks.wordpress.com/library-2/scope-probe-reference-material/

author: macboy
author_rank: Super Contributor
timestamp: September 05, 2017, 06:16:57 pm
content: Quote from: tggzzz on September 03, 2017, 08:09:10 am+1Even a very good 10M probe with "only" 10 pF tip capacitance will present a 64 ohm load at 250 MHz and 32 ohms at 500 MHz!It is no wonder that 10M passive probes above 500 MHz are all but non-existent. Tek has one that has "only" 4 pF at the tip, and is good for 1 GHz, if you are OK with 40 ohms of loading, but at $1k its cost is well into active probe territory.