> 1 GHz DIY differential probes

[the Willows]

Your are the best.
Thanks!

[nctnico]

The first batch of 9 probes is ready to go. The product name has become 'DIP1400' (DIfferential Probe 1400MHz). The bandwidth is +/-3dB up to 1.4GHz.



Datasheet:
http://www.nctdev.nl/NCT%20Instruments%20DIP1400%20V1.0.pdf

The final price is 125 euro ex. VAT ex. Paypal / wire transfer fees. Shipping in Europe is 16 euro, worldwide 27 euro including insurance.

[paul67]

Looks great nctnico :-)
PM Sent with purchase request...

[rsjsouza]

Great work, Nico! It will be on my wish list as my finances for hobbies are quite depleted at the time.

I read the datasheet and spotted a couple of typos:
Page 3: pads cannot be torn off very easily

Page 6: A more coarse measurement of the bandwidth

One question:
Page 4: do you have a characterization for the worst case scenario on the table?

Again, great work!

[paul67]

Thanks for the delivery of the probe, Nico. It works really nicely! I'm very happy with it. I wondered, what do you do with the LMH3401 inverting output... connect directly to 0V, or...?
I looked at the datasheet but couldn't see guidance for using in single-ended output mode.

[nctnico]

Thanks for the delivery of the probe, Nico. It works really nicely! I'm very happy with it. I wondered, what do you do with the LMH3401 inverting output... connect directly to 0V, or...?
I looked at the datasheet but couldn't see guidance for using in single-ended output mode.

The inverted output is terminated to ground with a (in total) 50 Ohm resistor so both output see (about) the same load.

[Evodad]

Hi ntcnico,

Any chance you have any probes left ?
This was an interesting thread. Why did it not survive longer ? Any spin-offs ?

// Per

[nctnico]

Hi ntcnico,

Any chance you have any probes left ?
This was an interesting thread. Why did it not survive longer ? Any spin-offs ?

// Per

Actually I have 20 new probes fresh from the assembler.

[Evodad]

That was good news 

Any modifications since the last batch ?

May I buy 2 of you ?

)) Per

[teomondo]

Dear ntcnico
Is DIP1400 1.4GHz differential probe currently avaliable?
I have an Operating manual dated 2019 any new version avaliable?
What about the price of DIP1400 1.4GHz differential probe and how I can buy it.
Thanks for your answer
Roberto

[KE5FX]

Unsolicited testimonial: having used it for a while now, Nico's probe works really well.  It's comparable to the Tek P6248 at a small fraction of the size/cost.  If you do anything with differential signals -- or just want an active probe in general -- it's definitely worthwhile.

(Edit: by "size" I'm not referring to the probe head, but to the large box at the other end of the P6248.  When I use the P6248 with my HPAK scope, I also have to find room for an even-larger Tek 1103 power supply.  The DIP1400's probe head is somewhat bulkier than the P6248's, but not excessively so, and it can be powered by the scope's USB jack.)

[tautech]

Unsolicited testimonial: having used it for a while now, Nico's probe works really well. 

Yeah but where is he ? 
Not logged in for nearly a month so hope this C thing hasn't caught up with him.
Stay safe and be careful out there. 

[Cerebus]

Unsolicited testimonial: having used it for a while now, Nico's probe works really well. 

Yeah but where is he ? 
Not logged in for nearly a month so hope this C thing hasn't caught up with him.
Stay safe and be careful out there. 

Last seen being a bit argumentative with Simon, so his temporary absence might have less ominous overtones.

Or he might just have got sick of the sight and sound of some of us and wanted some peace and quiet, can't really blame him if he has. 

[rsjsouza]

Unsolicited testimonial: having used it for a while now, Nico's probe works really well. 

Yeah but where is he ? 
Not logged in for nearly a month so hope this C thing hasn't caught up with him.
Stay safe and be careful out there. 

Last seen being a bit argumentative with Simon, so his temporary absence might have less ominous overtones.

Or he might just have got sick of the sight and sound of some of us and wanted some peace and quiet, can't really blame him if he has. 

I suspect I might have contributed a bit also to his (hopefully short) self appointed vacation... We were sparring a bit about 'scopes and perhaps it was time for a break. I hope he eventually comes back, as he has a lot to contribute and in general he seems to be a nice fellow.

[Kean]

I was thinking that once he was happy with the design he would list it on his Tindie store.  Still only has his CP2100 dual channel current probe listed.
And now I have a Micsig CP2100B it might be confusing to have an NCTi CP2100...   

[Noy]

Nice thing. I'm also interested to get one.

[2N3055]

I went and checked, he hasn't been on EEVBlog for almost a month. I hope he's OK, and only just busy...

[Noy]

Any news here?

[sciguy14]

I would also like to express my interest in purchasing two of these!

[nctnico]

I went and checked, he hasn't been on EEVBlog for almost a month. I hope he's OK, and only just busy...

I'm OK (and busy). I have been cutting back on posting on EEVblog though.

About the probes: I have these in stock ready to ship out. PM me when interested in purchasing.

[Noy]

I'm interested in one but currently I'm unsure if it is the right probe for my needs.

I only have 350MHz scopes (Rigol MSO5000 (external termination) / Hameg HMO3524(internal 50 Ohm temination)).

I need a probe to measure / qualify µSD signals in SDR104 mode somtetimes eMMC in HS400 mode (200MHz clk)...

Sometimes "slow" LVDS / MIPI without eye measurments (cant produce eyes on my scopes)..

Currently i only have passive 350MHz probes (they have too high loading for the 200MHz clk) / Micsig 100MHz high voltage differential probe (divider too high for the small 1.8V signals)..

I think two single ended active probes with >=350MHz BW with High resistance and low capacitance input for low loading would be the best fit for my needs. I can use 2 probes + math to measure LVDS/MIPI.

And for the "fast" SDIO signals i use both probes to measure 1 Data + CLk at the time.

So your differential probe has 2k Ohm input impedance? I think that is to low for me? And the 1.4GHz is over the top for my scopes..?

So has anybody another good solution for my needs? A DIY active probe with qualified behaviour (i can build one myself but i don't have equipment to measure the bandwith / impedance) and not too expensive?

Or is the DIP1400 useable for my needs?

[0xdeadbeef]

I'm using the differential probe from Elektor 4/2017 by Alfred Rosenkränzer discussed earlier in this thread. It has slightly different specs (~5kOhm differential resistance), but should be somewhat comparable.
At work, I'm using these probes mainly to measure a 40MHz LVDS signal  (MSC aka "microsecond channel") on a 600MHz LeCroy. Compared to the default 500MHz passive LeCroy probes, the difference is like night and day. I.e. with the passive probes, the signal looks like a distorted sine and with the active probes, it's a nearly perfectly rectangular signal.
Actually I also use the probe for single ended measurements (i.e. "-" connected to GND) when very steep edges are involved and when the capacitance of the passive probe would somewhat invalidate the measurement.
IMHO, an active probe with low capacitance is always worth it even on a 200MHz scope when looking at sharp edges. Of course if you don't need a differential probe, there might be cheaper options.

[tggzzz]

I'm using the differential probe from Elektor 4/2017 by Alfred Rosenkränzer discussed earlier in this thread. It has slightly different specs (~5kOhm differential resistance), but should be somewhat comparable.
At work, I'm using these probes mainly to measure a 40MHz LVDS signal  (MSC aka "microsecond channel") on a 600MHz LeCroy. Compared to the default 500MHz passive LeCroy probes, the difference is like night and day. I.e. with the passive probes, the signal looks like a distorted sine and with the active probes, it's a nearly perfectly rectangular signal.

I expect you mean a 40Mb/s LVDS signal. The maximum frequency will be much higher, dependent solely on the transition time.

It is unsurprising you see a distorted waveform, given that a *10 "10Mohm" impedance probe has a (capacitive) input impedance of <100ohms at the frequencies you are likely to see on an LVDS signal.

A pair of resistive divider Z0 probes would be a better bet, since they have a much lower capacitance and a well defined input resistance of 500ohms (*10) or 1000ohms (*20). They are easy to make at home.

[nctnico]

I'm interested in one but currently I'm unsure if it is the right probe for my needs.

I only have 350MHz scopes (Rigol MSO5000 (external termination) / Hameg HMO3524(internal 50 Ohm temination)).

I need a probe to measure / qualify µSD signals in SDR104 mode somtetimes eMMC in HS400 mode (200MHz clk)...

Sometimes "slow" LVDS / MIPI without eye measurments (cant produce eyes on my scopes)..

Currently i only have passive 350MHz probes (they have too high loading for the 200MHz clk) / Micsig 100MHz high voltage differential probe (divider too high for the small 1.8V signals)..

I think two single ended active probes with >=350MHz BW with High resistance and low capacitance input for low loading would be the best fit for my needs. I can use 2 probes + math to measure LVDS/MIPI.

And for the "fast" SDIO signals i use both probes to measure 1 Data + CLk at the time.

So your differential probe has 2k Ohm input impedance? I think that is to low for me? And the 1.4GHz is over the top for my scopes..?

Or is the DIP1400 useable for my needs?

I think the DIP1400 is useful for your purposes. One of the advantages of a differential probe is that you get the signal between two point (close together) and not via a ground point connected to a long lead. For example: I have used the DIP1400 to troubleshoot a power supply problem on a SOC design because I wanted to make sure I wasn't looking at spikes induced into the ground connection. 2k Ohm should be OK for almost every digital signal; one of the design goals was to make the input impedance high enough so the amplitude error on signals using a 50 Ohm (single ended) connection is below 10%.

[0xdeadbeef]

I expect you mean a 40Mb/s LVDS signal. The maximum frequency will be much higher, dependent solely on the transition time.

Well, one of the LVDFS channels is a 40MHz clock. So since when is frequency only a valid unit for sine waves? Of course the sharp edges have much higher frequency components. No need to mention that in this board, do we?

It is unsurprising you see a distorted waveform, given that a *10 "10Mohm" impedance probe has a (capacitive) input impedance of <100ohms at the frequencies you are likely to see on an LVDS signal.

For a 11pF probe, a 400MHz component will "see" a resistance of ~36Ohm, while the DC components will "see" 10MOhm. How is it surprising that this distorts the waveform?
Anyway, have you ever actually tried to measure a 40MHz square wave with a passive probe?

A pair of resistive divider Z0 probes would be a better bet, since they have a much lower capacitance and a well defined input resistance of 500ohms (*10) or 1000ohms (*20). They are easy to make at home.

A typical active probe has like 0.5pF capacitance, so anything you attempt to attach it somewhere will actually add a capacitance in the same magnitude or higher. I don't see how a purely resistive probe would help there. Plus, its low resistance makes it problematic for digital outputs which might as well create a burst clock only now and then.