Recent Posts

1

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

« Last post by ebastler on Today at 06:59:18 pm »

900 switches when all 4 ch on and MSO

I see. Yeah that's kinda expected.
A hacked 800 doesn't do it, it stays on 312.5.

No, it's not really expected. The DHO900 is the only scope I'm aware of which behaves this way.

In typical DSOs, the analog sampling rate is limited by the ADC. (Which is shared across two or four channels, hence sampling rate per channel drops as you activate more analog channels.) But the digital channels are read separately -- they do not need the ADC, and hence don't eat into the ADC bandwidth available for analog sampling.

In contrast, the DHO900 series seems to be limited by the bandwidth of the FPGA/DRAM interface. It uses the same ADC as the larger DHO1000 series, yet runs it at only 1.25 instead of 2 GHz. And when you want to read digital data in parallel, that eats into the available sampling rate.

A hacked DHO800 will behave the same -- as soon as you actually connect and enable a digital probe. Mechatrommer has done that and can comment.

2

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

« Last post by BlownUpCapacitor on Today at 06:58:55 pm »

Perhaps something is not biased properly in the oscillator? But I wouldn't know how to check that as that would be INSIDE the op amps.

Check if a trigger output signal is present while oscillating, and during the failed oscillation.

Also use the VCF function to push the oscillator into its failure zone without using the dial.

Report back.

3

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

« Last post by shapirus on Today at 06:57:48 pm »

sin(x)/x will start to go wrong at sample rate / 2.5

That video shows exactly what the math says it should.

Yeah, and it actually works fine up to 500 MHz at 1.25 GSa/s (save for the greatly reduced amplitude because of the input filter).

4

Test Equipment / Re: Handheld meter robustness testing

« Last post by armandine2 on Today at 06:55:12 pm »

I do have a cheap digital caliper ... just not very experienced, and being a bit cautious/ginger - the reading depends a bit on how much pressure I apply to the jaws. It's probably actually 1.5 mm, that's what I get when applying more pressure.

I don't have a great setup for the close-ups, anyway, some more switch detail ...

Verniers cheap or not can be awkward to get at the right angle, I find, best to use a micrometer.

5

Power/Renewable Energy/EV's / Re: Output Capacitor Selection for Buck Converter

« Last post by Faringdon on Today at 06:54:58 pm »

I once did a 1MHz vicor module PSU for a co....they wanted the Cout  with a couple of 4.7uF MLCC's...i changed it for a few 1uF MLCCs...it was something like a quarter of the capacitance...and the output voltage ripple went  DOWN!.
(Because ESL was bigger in the higher capactiance MLCCs).
When  i reported it to them..they said i must have done it wrong , and fired me ...but i was explaining the situation as we walked along the corridor to the exit door...and they decided to look into it.....they took me back on.

6

FPGA / Re: USB BLASTER (FTDI245 vs ch552x) Quartus “No Hardware”

« Last post by coromonadalix on Today at 06:52:05 pm »

do they get recognized with the vid pid ??   FTDI had some memory on their ic to register  any vid pid you wanted

7

Metrology / Re: Stability of 5V references compared to AD586LQ

« Last post by Kleinstein on Today at 06:48:32 pm »

Another problem with konstantan wire is that it is hard to solder. Maganin wire is easy to solder.

8

General Technical Chat / Re: Fun for nerds

« Last post by Sal Ammoniac on Today at 06:48:23 pm »

9

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

« Last post by Fungus on Today at 06:47:30 pm »

It however starts to fail well below Nyquist (which is 156.25 MHz at this sampling rate): the displayed signal begins to have lower frequency noise at about 100 Mhz and it becomes next to useless at ~130 MHz.

sin(x)/x will start to go wrong at sample rate / 2.5

That video shows exactly what the math says it should.

10

Projects, Designs, and Technical Stuff / Re: DIY Digital Caliper

« Last post by MitkoDyakov on Today at 06:40:55 pm »

Hardware - the footprints for the t-scale and sensor and also gerbers and schematics

Thanks for sharing, But it would be nicer if you could share the Kickad files for schematics and PCB, since We can modify it easier.

You can find it in BluePillCaliper/Hardware /Footprints - KICA