Author Topic: Show us your square wave  (Read 205355 times)

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Offline TiN

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Re: Show us your square wave
« Reply #325 on: December 21, 2016, 10:15:34 am »
Upgraded/downgraded my scope at work. Not a fan of new Tek UI, so much button dodging and multilevel menus..  :wtf: Old Windows/PPC-based TDS5034B was sorta easier.

Square wave measure of own calibration output in the TDS7704B : ~260ps into 50Ohm.
Brand new MDO4054C with same 1:1 BNC cable measuring same cal output of TDS7704B : ~800ps into 50 Ohm.
« Last Edit: December 21, 2016, 10:18:31 am by TiN »
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Online tggzzz

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Re: Show us your square wave
« Reply #326 on: December 22, 2016, 11:05:24 pm »
Output from a Tek 1502 TDR driving a Tek 485, Tek 2465, and Tek 2445B, all terminated with an internally with 50ohms. The Tek 1502 risetime is ~50ps, and the Tek 485 timebase is 1ns/div with a risetime of ~900ps.

The Tek 1502 output shows two clear phases
  • one in which it determines the "bias point" of the tunnel diode
  • the other in which is biassed to just below that point and then triggered to produce the pulse that is measured
Given the duration of each phase, 37us, it is a testament to the Tek engineers of >40 years ago that the 1ns edge is so clearly visible.
There are lies, damned lies, statistics - and ADC/DAC specs.
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Offline lty1993

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Re: Show us your square wave
« Reply #327 on: December 23, 2016, 07:24:40 am »
Source:
1. Rigol MSO2302A-S Internal Source (Attachment 1) [15Mhz]
2. Rigol DG4202 (Attachment 2 and 3) [25Mhz and 60Mhz]

Display:
1. Rigol MSO2302A-S

Direct Coax and 50Ohms load.
« Last Edit: December 23, 2016, 07:28:59 am by lty1993 »
 

Offline guenthert

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Re: Show us your square wave
« Reply #328 on: December 24, 2016, 08:36:28 pm »
For contrast and completeness' sake below results I got from an Analog Discovery 2 with the BNC adapter module:
(output shunted with built-in 50Ohm terminator, set 1V symmetric square wave)
input was not terminated (uses ~1MOhm "high impedance" input, DC coupled)

top to bottom:

- 8' BNC cable, 5MHz (the signal generator offers 10MHz, but then not much of a square is left)
- 8' BNC cable, 1MHz
- 100MHz 10x probe, 1MHz (system is in a bit of a noisy environment, I think the probe picks up some RFI)
- 100MHz 10x probe, 5MHz
- 8' BNC cable, input terminated via T-piece and 50Ohm terminator, 5MHz
- FFT of the last one
« Last Edit: December 25, 2016, 01:15:28 am by guenthert »
 

Offline capt bullshot

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Re: Show us your square wave
« Reply #329 on: February 02, 2017, 01:50:45 pm »
I believe, it's been done before, but I did hack a few components together to produce a quite nice square wave. The basic concept is a HC14 oscillating at a non important frequency and driving a LVPECL level translator. It's outputs have emitter resistors of 100R to GND, and AC coupled (10uF || 100nF) to a back terminated 50 Ohm line (Rs = 43R according to the OnSemi application note. Running some RG174 to the 50R scope input shows a clean trace, the scope reads about 300ps rise/fall time (I don't have access to a faster than 1GHz scope). So nothing very exiting, but easy to build, took about one hour to complete.
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Offline Howardlong

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Re: Show us your square wave
« Reply #330 on: February 02, 2017, 03:39:02 pm »
What's the prototyping board you're using?
 

Offline capt bullshot

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Re: Show us your square wave
« Reply #331 on: February 02, 2017, 07:00:56 pm »
This is a SP3T-50x50-G from BusBoard Prototype Systems. It has a copper plane on the bottom side, 50x50 mils pads on the top side and non-plated holes every fifth pad or so. It is a thin PCB, can be cut using a paper scissor.

 
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Offline jpb

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Re: Show us your square wave
« Reply #332 on: February 02, 2017, 07:03:57 pm »
I've been using the LTC6957 demo board. Unfortunately I'm in the middle of moving house (again) so everything is packed up so can't show anything other than this very bad photo.

The rise times for LVCMOS output is around 700 to 800 psecs and much less for the LVPECL version.

http://www.linear.com/product/LTC6957-1
« Last Edit: January 12, 2019, 12:35:16 pm by jpb »
 

Offline Howardlong

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Re: Show us your square wave
« Reply #333 on: February 02, 2017, 10:42:13 pm »
This is a SP3T-50x50-G from BusBoard Prototype Systems. It has a copper plane on the bottom side, 50x50 mils pads on the top side and non-plated holes every fifth pad or so. It is a thin PCB, can be cut using a paper scissor.

Very nice, I'm sure I'll be adding a couple of those onto my next Mouser order.

Edit: do they spec the Er?
 

Offline capt bullshot

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Re: Show us your square wave
« Reply #334 on: February 03, 2017, 06:09:56 am »
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Online tggzzz

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Re: Show us your square wave
« Reply #335 on: February 03, 2017, 10:01:09 am »
This is a SP3T-50x50-G from BusBoard Prototype Systems. It has a copper plane on the bottom side, 50x50 mils pads on the top side and non-plated holes every fifth pad or so. It is a thin PCB, can be cut using a paper scissor.

Very nice, I'm sure I'll be adding a couple of those onto my next Mouser order.

Edit: do they spec the Er?

I would have thought that the variability of anything you would use as conductors on the topside would be more significant than the likely difference in Er. I'd simply assume 4.2.
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
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Online sorenkir

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Re: Show us your square wave
« Reply #336 on: March 25, 2017, 04:55:12 pm »
Hi,

I have discovered that BG7TBL's 35M-4.4G USB Signal Source (based on ADF4351) generates a quite nice square wave with fast edges around 200ps.
Measured with my TDS520B-500MHz (in fact ~650MHz --> Tr=~538ps)

Michel.
 

Offline Muxr

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Re: Show us your square wave
« Reply #337 on: March 26, 2017, 05:13:05 am »
Don't really have a fast pulse generator, but I can show some relatively fast rise time on my RF gen.. as captured by the RTM 1054

I can reliably see the signal up to 1.2Ghz.. even up to 1.8Ghz is somewhat visible but the trigger starts failing pretty often at that frequency.
 

Offline AlphaRomeo

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Re: Show us your square wave
« Reply #338 on: April 16, 2017, 09:41:59 pm »
Thank you all for the postings.  I just got the Siglent SDG2042X, at 1Mhz the square wave is acceptable,  at 5Mhz starting to degrade very bad, etc. I thought I got a defective device. I need to dig more into how these things works. How the square wave is generated, etc. Reading your post helped me understand  that I did not get a defective generator.
« Last Edit: April 16, 2017, 10:14:24 pm by AlphaRomeo »
 

Offline MrW0lf

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Re: Show us your square wave
« Reply #339 on: April 17, 2017, 06:52:34 am »
Thank you all for the postings.  I just got the Siglent SDG2042X, at 1Mhz the square wave is acceptable,  at 5Mhz starting to degrade very bad, etc.

Might get better results with ARB mode=DDS and using square from built in ARB wfms.
 

Offline ADT123

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Re: Show us your square wave
« Reply #340 on: April 28, 2017, 08:24:07 am »
Heard a colleague say "now that's a fast edge"



« Last Edit: April 28, 2017, 08:39:57 am by ADT123 »
Disclaimer: I have worked for Pico Technology for over 30 years and designed some of their early oscilloscopes. 

We are always recruiting talented hardware and software engineers! Happy to answer Pico related questions when time permits but here as electronics is a hobby
 
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Offline amspire

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Re: Show us your square wave
« Reply #341 on: April 28, 2017, 01:27:32 pm »
ADT123,

was that sampling scopes one of your projects? Having a go at building a sampling scope has always been something I have wanted to try. The principles are so simple, but I am sure it took a massive effort to get that 25MHz bandwidth. The waveform really is amazingly clean.

Historically, this is the technology that allowed scopes to be built with GHz bandwidths when scope mainframes were struggling to reach even 1 MHz bandwidth.

A pity the price is so out of reach of the hobbyist. I have always thought this is potentially a very cheap technology if the market was big enough - maybe not for 25GHz, but 5GHz bandwidth would be pretty good. 

Am I delusional?  :)

Richard.
 

Offline WackyGerman

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Re: Show us your square wave
« Reply #342 on: April 29, 2017, 08:22:20 am »
Here are my results of measuring a 10 MHz squarewave from my Siglent SDG1010 with three different bnc cables .
 

Offline MrW0lf

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Re: Show us your square wave
« Reply #343 on: April 29, 2017, 07:48:43 pm »
I know nothing about tech side... but as a concept, maybe it is possible to hack analog frontend of cheap USB scope having ETS? For example ~100EUR Pico 2204A has 2GSa/s ETS listed. Logically software is there, timing stuff is there...
 

Online Electro FanTopic starter

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Re: Show us your square wave
« Reply #344 on: April 30, 2017, 06:40:06 am »
Heard a colleague say "now that's a fast edge"



That looks like a fast rise time but to keep things apples to apples most of the measurements here have been at 10% and 90% rather than 20% and 80%.
 

Offline ADT123

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Re: Show us your square wave
« Reply #345 on: April 30, 2017, 08:39:55 am »
Richard - I designed most of the real time scopes with a parallel port starting with the ADC-10 in 1991 and hung up my soldering iron around 2001 with the ADC212/100 which included repetitive ETS sampling (https://www.picotech.com/about/history).

As for a lower cost / lower bandwidth sampling scope its an interesting idea.  Above a few GHz every component gets expensive if you want to do the job properly (connectors, PCB etc) but below say 5GHz things get a lot cheaper.  Will have a think.  Guess it depends on the market - hobby users often go for 2nd hand boat anchors which can be cheap and to be honest not everyone knows how to drive a sampling scope (splitters for trigger signals etc).

10/90 vs 20/80 rise time - thats a fair cop.  I just borrowed a waveform so when I get a chance will see if I can do better.
Disclaimer: I have worked for Pico Technology for over 30 years and designed some of their early oscilloscopes. 

We are always recruiting talented hardware and software engineers! Happy to answer Pico related questions when time permits but here as electronics is a hobby
 
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Offline pigrew

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Re: Show us your square wave
« Reply #346 on: May 02, 2017, 12:16:16 am »
Tabor 8025, programmed to be 1Vpp, 50 MHz, 50 ohm terminated. 10%/90% rise time is 5.2ns, fall is 4.65ns.
 

Offline ADT123

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Re: Show us your square wave
« Reply #347 on: May 02, 2017, 07:25:38 am »
10/90 rise time (see comment from Electro Fan a couple of posts again).  Scope rise time is 14ps, pulse rise time is 10ps.  Combined gives 18.74ps.

Please dont try to beat this - not sure I can respond with anything faster!



Disclaimer: I have worked for Pico Technology for over 30 years and designed some of their early oscilloscopes. 

We are always recruiting talented hardware and software engineers! Happy to answer Pico related questions when time permits but here as electronics is a hobby
 

Offline MrW0lf

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Re: Show us your square wave
« Reply #348 on: May 02, 2017, 11:08:15 am »
Noticed that on last Pico screenshot sampling rate is mere 10TSa/s, while on previous 16TSa/s ::) But guess both are adequate being "slightly" over Nyquist :P
 
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Online Electro FanTopic starter

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Re: Show us your square wave
« Reply #349 on: June 02, 2017, 10:50:22 pm »
10/90 rise time (see comment from Electro Fan a couple of posts again).  Scope rise time is 14ps, pulse rise time is 10ps.  Combined gives 18.74ps.

Please dont try to beat this - not sure I can respond with anything faster!



It is very competitive with the best rise time we have previously seen (~16ps by EV):

https://www.eevblog.com/forum/testgear/40-ps-rise-time/msg935446/#msg935446
« Last Edit: June 02, 2017, 10:59:13 pm by Electro Fan »
 


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