Recent Posts

1

Projects, Designs, and Technical Stuff / Re: (Yet Another) DIY Multislope ADC

« Last post by Kleinstein on Today at 09:15:25 am »

It is not a good idea to have different resistors for the input and reference currents. To get compensation of the switch resistance TC they should be the same.
Instead of a smaller resistor for the references a higher voltage (e.g. 14 V = 2 x raw reference) is the better way.

The times for RDN and RDNP should not get down all the way to zero. It would be more like 4 or 5 cylces as a minimum to allow for settling. For the result a constant added part is not important as one will subtract a zero reading anyway.
For the uncertainty the contributions from the parts (run-up, rundown difference of reference, rundown sum of reference and the residual ADC) is the relevant factor. With 1 PLC (20ms) the runup step are some 1/2000 for the full scale. With longer integration even more comes from the run-up. The run-down makes up some 2 run-up steps and in the current configuration some 120 cycles, the residual charge ADC is for 1 of the rundown steps or some 10 ppm of the FS.

2

General Technical Chat / Re: Russia and China to Build a Nuclear Plant on the Moon.

« Last post by tggzzz on Today at 09:13:59 am »

The moon doesn't rotate, so no night or day.

Of course the moon rotates. Once a month.

The dark side of the moon is a music album, not any description of reality.

Which was what I meant to convey, but stuffed it up.
I was thinking about how the moon presents the same side to us, & that there was always some part of the moon lit by the sun.
I neglected the fact that we don't see all of the same side, all of the time.

Correct. We see more than 50% of the lunar surface.



Since the 1850s this has been used to show remarkable stereoscopic views of the moon, originally for Brewster viewers. Get out your red-blue anaglyphs, and see the football

3

RF, Microwave, Ham Radio / Re: WSJT-X on Pi

« Last post by pdenisowski on Today at 09:11:47 am »

I pulled out a new SD card and will just start over.

This is the way   I have a dedicated SD card for WSJT-X on Pi.

Glad to hear it's working!

4

Test Equipment / Re: New 2ch pocket DSO+SG - Zeeweii DSO2512G

« Last post by Aldo22 on Today at 09:11:10 am »

1) What does “RTAuto” mean in the upper right corner of the screen, which appears when you long press the Auto button.

I don't have this on my older FW version.
I assume it means "real time auto".
So it does "auto" whenever the signal changes without you pressing the button. Just a guess.
Try if the scales change automatically with different frequencies or amplitudes.

P.S. I wanted to send images of my board and "RTAuto", but I couldn't. How can I send an image here when replying to a post?

-> Attachments and other options

5

Test Equipment / Re: Siglent SDS800X HD - Using SCPI with python via telnet to measure with 2 gates

« Last post by eTobey on Today at 09:08:57 am »

This is a good way to achieve some functions that cannot be done by oscilloscope through python.
It takes a long time for oscilloscope to add functions, while scripting code takes a short time and is very flexible.
Others can also add their own needs and scripts.   

While not familiar with python, SCPI and the scope, it took me like 4 hours. It might be flexible, but it is very sloooow. About 2 measurments per second.

Maybe SCPI speed can be improved?

6

Test Equipment / Re: SDS800X HD Bug Reports + Firmware

« Last post by eTobey on Today at 09:06:46 am »

From eTobey's side, it might feel like he is doing work for Siglent?

Actually, some kind of "bug bounty" program would be a nice touch. Users who find and characterize bugs are providing a service to Siglent and to the user community, after all.

Dear Siglent -- I would settle for an SLA1016 logic probe, ideally with an extra set of the better grabbers! 

Actually a function generator would be my preferred item at the moment. Also i wouldnt find so much bugs then, which is something me and others would prefer anyway. 

7

Test Equipment / Re: Choosing between entry-level 12-bit DSOs

« Last post by gf on Today at 09:03:30 am »

Now work from there to something a tiny bit below that ... you'll go between zero crossings and peaks over time, and get an AM effect as seen in that video.

It looks like most interpolation filters are realized as Nyquist Filters, having a symmetric N*SR...(1-N)*SR transition band, where 0<N<0.5, and SR is the sample rate. This is fine for frequencies below N*SR, but leads to the observed "AM effect" for frequencies in the N*SR...0.5*SR range.

An interpolation filter with a N*SR...0.5*SR transition band would avoid that, and only reduce the amplitude of frequencies in the transition band. However, the drawback is that it requires about 4x as many non-zero filter taps as a Nyquist filter with the same N.

And in general, the closer you want to get to 0.5 with N, the more filter taps you need. There is no fixed N set in stone, but there are practical considerations/limits.

8

General Technical Chat / Re: Russia and China to Build a Nuclear Plant on the Moon.

« Last post by Coordonnée_chromatique on Today at 09:00:03 am »

high power reactor cooling in space will be biggest challenge because there is no way to dissipate excess heat

Whether a high powered nuclear reactor can be cooled via radiation alone, now that's an engineering challenge.

Hello, this is an idot question but, if you radiated energy hits nothing there is no heat transfer ?

9

Repair / Re: Tektronix DPO4054 stucked at tektronix splash screen

« Last post by ApertureScience on Today at 08:59:22 am »

I remeasured all 75Ohm termination resistors and some seem to measure around 38Ohm. So probably two lines shorted together. I took off all associated ram and no change. So complete reball of U370 it is.  Now waiting for some BGA stencils and solder balls.

10

Repair / Re: Tek FG502 fails at high frequency end of dial - help needed!

« Last post by gcwills on Today at 08:56:32 am »

Thanks again for your thoughts!

The trigger out signal is present while the oscillator is working and fails when the oscillator fails.
Good suggestion re the VCF function. I set the frequency dial to 1 and applied voltage from my bench supply to the VCF input. As expected, the frequency increased as the voltage increased and when the frequency approached the equivalent frequency set by advanced setting of the frequency dial the oscillator stopped. So yes, applied voltage into the VCF input produced exactly the same result.

I have spent quite some time on this issue today and have tested just about all the transistors and diodes in the oscillator circuit to no avail. The fault does not seem to be related to the DC settings as the tests with the VCF reflect. However, one possible clue to the fault was discovered - the collector voltage at Q292 which switches the ramp voltage on and off measured low (30-140mV depending on the multiplier settings) to measuring -3V when the oscillator stopped. The challenge with fault finding this kind of oscillator circuit is it is a closed feedback system so any issue in that loop is reflected everywhere in the loop. I found a very helpful resource on the Tek Wiki here: https://w140.com/tekwiki/images/2/2f/Repair_FG502_English.pdf   that refers to the closed loop scenario.....