Recent Posts

1

Test Equipment / Re: Standardised Way To Test Oscilloscope Screen Update Rate

« Last post by EEVblog on Today at 07:56:08 am »

This really is a non-issue which has been discussed before. Any form of high-waveform update rate will have a certain amount of persistence time to make sure the signal stays on the screen long enough to be noticed. Think in order of magnitude of 200ms. Anything below is likely to be missed. If you think about it and think back about the relative long fade times of phosphorus used in CROs, you'll come to the conclusion that the display update period can't be a parameter in the process which shows the signal.

Sure, but why does any scope update the display faster than 200ms then?

2

Microcontrollers / Re: SD Card reliability in SPI mode

« Last post by TizianoHV on Today at 07:54:59 am »

I've used a 2GB Kentron and a 8GB Kingston micro SD card + SdFat for my datalogger (Arduino nano every).
I wrote into the same cards for weeks, 50 times per second (2kBytes/s), multiple times without any issue.
Maybe smaller cards are better for such applications?

Code: [Select]

...
dataFile = SD.open(filename, O_CREAT | O_APPEND | O_WRITE); //Open file only once
...

while...{
  ...
  dataFile.println(dataString);
  SDbuffCount++;
  if(SDbuffCount > SDbuffDim){
      dataFile.flush();        //Flush, up to 5 times per seconds
      SDbuffCount = 0;
  }
}
dataFile.close();


3

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

« Last post by Fungus on Today at 07:53:03 am »

Can the TSA do amplitude modulation?
Put in some AM at about 10% of the frequency.

It only supports a limited number of amplitude levels (I think 8 or so) for the the modulating signal, so it's a "stair step sine wave".
And the modulating signal is limited to 10 kHz.

EDIT: See also Erik's video: https://youtu.be/U2cw0bmuSLM?t=239

The TinySA supports 8-point interpolation, while the Ultra can muster up to around 128 points depending on modulaton frequency.

Ok, no problem.

I'm just wondering how the Siglent is cheating to get that display. The Rigol isn't doing anything wrong, it's doing the correct math for the limited information it has.

The original Signal can be reconstructed with much wider filters but they'll only work if the signal is perfectly periodic.

I was wondering what happens if the signal isn't periodic. It could go very wrong.

4

Power/Renewable Energy/EV's / Re: 5 out of 6 vendors are scamming people with wrong crosssection of cables

« Last post by eTobey on Today at 07:50:45 am »

... I ask because measuring cross section of a multi-stranded wire is not trivial at all. Which is also why, to answer your question: I have never checked. I think the risk of me measuring incorrectly would be larger than the manufacturer lying.

Current, voltage drop and ust a few calculations, and then you have the cross section. Nowadays with internet i would call this trivial.

I could not find the very same measurments, but i can give you an example, that is as good. (Scamed by the PCB manufacturer, as he did not mention a tolerance of 20%. Seems to be a chinese thing, yes).

5

Beginners / Re: LM317 Based Digitally Controlled Power Supply

« Last post by Kleinstein on Today at 07:50:02 am »

The circuit with the LM317 as a power transistor replacement would need a negative supply for the OP-amp. Otherwise it would not work below some 1.2 V and could not limit the current with these low voltages (e.g. with a short).

6

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

« Last post by Fungus on Today at 07:47:23 am »

There are specific posts in this thread covering most of this, but a summary doesn't hurt.

Rigol Pros: HDMI, VESA mount, WiFi built in.

Smaller size, battery option, more accessible UI, easy/neat Wifi with web/ftp access to the 'scope...

Rigol can go to 100MHz (or 125MHz) but is severely limited by its sampling rate.

Nope. Rigol can go to 280Mhz measured bandwidth, and shows signal far beyond that.

I wouldn't leave it at that bandwidth for general use but it's there if you need it and it only takes about 10 seconds to switch the model.

There's also 225MHz, 200Mhz and 125MHz options.

The lower sample rate sounds scary but when you're looking at real-life signals with probes clipped onto wires? Not so much.

(And there's no problem at all with 1 or 2 channels)

7

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

« Last post by Kleinstein on Today at 07:46:23 am »

There is no need for a super stable clock. The point is jitter over a time frame of some 10 µs. The switches and an optional buffer to improve the isolation would add a few ps of jitter anyway. So a standard crystal oscillator should be good enough.  The crystal directly at the RP2040 as for the RP-pico could have an issue with the internal state effecting the clock - I had this issue with the AVR and this caused quite some INL error (e.g. 10 ppm range). Chances are 12 MHz directly with no PLL could be fast enough for the ADC, though this would not allow to use the USB while using the ADC.

8

Repair / Re: Mig welder wire feeder controller board not working

« Last post by TERRA Operative on Today at 07:45:12 am »

A little off topic but wire feed related. Since repairing a no wire feed problem with my brother's WIA 250i, it now will stop feeding if an arc doesn't strike within a second of pulling the trigger. Seems to be a feature that has been activated somehow, but no mention of it in the manual. Not a problem in practice.

Apparently, the wire should feed normally for 5 seconds, then run at full speed (for feeding wire down the MIG Gun etc).
Might be an issue with the current sensing somewhere, but I unfortunately don't have access to the WIA service portal anymore to get the full schematics (if available).

9

Test Equipment / Re: New Hantek DSO2X1X models?

« Last post by Pin240 on Today at 07:41:41 am »

Working or not, after 3 boots (Wait until the second Hantek logo shows up, then another 5-10 seconds) the original file will be restored.

Thanks for the script

10

Projects, Designs, and Technical Stuff / Re: No interrupt from AS6501...

« Last post by dietert1 on Today at 07:41:08 am »

The app note source codes are in C and C is portable. As a proof of concept you could port the app note to your MCU. Probably you have support for the peripherals needed (GPIO, Interrupt, SPI..)
Coding in assembler can be a second step once it works.

Regards, Dieter