Cheap 10X inline BNC attenuator?

[Plasmateur]

Here are two examples of what I am looking for


The exact version
http://www.testpath.com/Items/Attenuator-BNC-50-Ohm-2W-2GHz-10X-117-010.htm

The cable version
http://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.

[Plasmateur]

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.

[tautech]

Look here:
https://www.eevblog.com/forum/buysellwanted/fs-us-misc-tek-parts-and-fairchild-voltage-regulator/

[Plasmateur]

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 a seen as a high impedance to the DUT, that will now work.

In which case. I need the 1M solution.

A 50Ohm attenuator won't work in a 1M system since the attenuator will have much lower impedance and hence will drag output voltage to practically zero.
An 1M attenuator won't work in a 50Ohm system either since the 50Ohm input load will drag the output of 1M attenuator ro practically zero.

Therefore, you need an attenuator specifically designed for your target measurement system.
For 1M case you mentioned, you need your attenuator to look like an 1M load from source when the sink is also 1M.
Impedance matching in 1M system is much less strict than 50Ohm systems, but nevertheless the source better sees a 1M load, in case you use attenuated probes (otherwise scale factor will screw up).
I would consider something like 1.125M resistor to ground at input side, then a 9M resistor from input to output, then the output is terminated in scope at 1M. You get exactly 10x reduction of voltage while the source still sees exactly 1M.
Of course, you need capacitors to compensate parasitic capacitance otherwise there's no way to get 200MHz.

Ahhh, 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.php

It 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.

[ADT123]

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

[Plasmateur]

 It would be useful to know why you are doing this.

https://www.picoauto.com/products/test-leads/101-attenuator

Ease 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.

[Plasmateur]

Ahhh, Just as I had suspected however I need the source to see 10M of impedance....or higher.

Are you trying to find a BNC inline attenuator or a probe itself? For a 10x probe, the source where the probe tip is probing sees 10M, then the probe's output is terminated to 1M. Therefore, if you are building an inline attenuator, its source (which is the 10x probe's output) should see 1M. Meanwhile, the attenuator will see a 1M impedance on its load.

Forgive 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-probe

For 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.

[markb82]

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

[alm]

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.

[tggzzz]

Ahhh, Just as I had suspected however I need the source to see 10M of impedance....or higher.

Don'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 significantly higher impedance

FFI, see https://entertaininghacks.wordpress.com/library-2/scope-probe-reference-material/

[macboy]

Ahhh, Just as I had suspected however I need the source to see 10M of impedance....or higher.

Don'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 significantly higher impedance

FFI, see https://entertaininghacks.wordpress.com/library-2/scope-probe-reference-material/

+1
Even 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.