Recent Posts

1

Test Equipment / Re: SDS800X HD Wanted Features

« Last post by eTobey on Today at 09:48:08 pm »

Any advanced user with some active Math channels.

A few more words would have been useful, and would have sounded much nicer...

From 8+ tabs there is a point that would make those buttons actually better than scrolling IMHO. But then i would say drop that timestamp (make it floating or whatever) and make those buttons slightly bigger, and have the fifth element beeing covered less.

How about making the tabs a tiny bit smaller too? There is some room in the middle.

2

Test Equipment / Re: Equipment Discounts from Saelig

« Last post by awakephd on Today at 09:44:28 pm »

I am about ready to pull the trigger on a scope. Could I also get the discount code? Thanks!

3

Projects, Designs, and Technical Stuff / Re: Accurate sine wave in terms of amplitude

« Last post by tggzzz on Today at 09:43:21 pm »

>Depending on your (apparently secret) requirements...

Or I simply don't know yet. Pretty much all the requirements (=the rest of the circuit) depend on what kind of signal I can generate. The frequency can be between 1-10kHz. Amplitude can be between 200mV and 5V. I don't know how much THD (or any other parameter) affects to the device. I need to finish the design, build the device and test. And then probably, re-design the circuit, build another device and test again. Maybe at this point I actually know all the key parameters, including if THD matters or not.

But I do know today that I am iterating options how to generate sine wave - as clarified in the initial message including an example circuit.

Quadrature oscillator might be "the fresh idea I was looking for". Just that none of the first examples I tried to simulate on LTspice didn't work. Like this one:
(Attachment Link)

Probably a simulation related issue - I need to analyze it further...

sw guy

Now why couldn't you have simply said that earlier? A lot of time would have been saved.

Your first task is system modelling, to calculate what should work.
Your second task is system design and simulation, to determine allowable tolerances.
Your third task is detailed design, simulation, to verify you can implement the system.
Your fourth task is to build and test.

You are asking us about task 3, without having done tasks 1 and 2. That is bound to fail, slowly and messily.

You are doing the equivalent of jumping straight into coding, without having requirements nor architecture. See the problem?

Once you have a successful system simulation, e.g. using a spice sine wave voltage source, you can build a lab prototype using an off the shelf function generator. Only after the lab prototype is.working does it become worth considering  implementing your own generator.

4

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

« Last post by awakephd on Today at 09:43:10 pm »

Well, I had planned to drop out of this discussion, in part because I still had a month to go before I would have funds in hand to make a purchase ... but unexpectedly the funds have arrived early, so now the pressure is on to make a choice ... so I am back to seeing if I have fully understood the pros and cons of each, choosing between the Siglent SDS804X HD and the Rigol DHO804.

There are many things that seem to point to the Siglent SDS804X HD as the obvious choice (2G sample rate; better math functions; more USB ports; fewer bugs?). However, to the extent that I have been able to follow the discussion above, at least some of the advantage of the Siglent seem to be tied to more advanced topics than I expect ever to get into. (Yes? No?)

Meanwhile, there are some features that the Rigol brings to the table that I find attractive, including the slimmer size, possibility of powering from a battery pack, HDMI output, easy addition of wifi capability. VESA mount might also be valuable for my limited workspace.

I am getting ready to read back through the extended threads that detail performance, bugs, desired features, etc. for each of the units, but in the meantime, I have three specific questions:

The last feature I noted for the Rigol leads to the first specific question for this post: Have I understood correctly that there is no way to add wireless to the Siglent other than through the ethernet port?

Second specific question: I seem to recall reading something that suggested that the probes that come with the Rigol 804 are better (? or have a higher BW rating?) than those provided with the Siglent. Is that true, and should I care?

Third specific question: I think I would likely want to "hack" either of these units up to 100MHz and greater memory depth. From what I am seeing, this seems to be easier for the Rigol than for the Siglent - true? (This also connects to the previous question - if I want to hack up to 100Mhz, are the probes going to make that less successful with one vs. the other?)

5

RF, Microwave, Ham Radio / fake MPF102s from AliExpress

« Last post by graybeard on Today at 09:41:59 pm »

I ordered some MPF102 n channel RF JFETs from two different vendors on AliExpress since domestic versions are no longer available.
What I got were remarked NPN BJTs, not JFETs.  See the attached images.

6

Test Equipment / Re: Cheap oscilloscope for checking mains power quality? Also logging equipment.

« Last post by adam4521 on Today at 09:41:23 pm »

For low cost power quality logging I've had some success using a commercial-grade electricity meter: Schneider PM5110/PM5111 for example which you can easily find used/surplus. Install into an adaptable box. Lower cost than a power quality analyser, and you can read out voltage, current and harmonic data to a computer via Modbus RS485 interface. But this will be a bit of a do-it-yourself project.

For RCBO/GFCI nuisance tripping, often this will be linked to a switching transition -- something being connected to the system or switched on, that creates a transient unbalanced current in the live and neutral conductors. For LED flicker, it's traditionally associated with unstable timing of 'phase cut' dimming: the lighting driver is interacting with the dimmer. If you really want to see what is going on you will want the oscilloscope, but you will need to convert the current signal you want to observe to a voltage signal. As electrician, you would be confident making up a circuit breakout box with a CT and suitable burden resistor inside? You might make a specific one for measuring residual current -- look for a 'zero sequence CT', which has higher sensitivity.

Multiple times on the forum we discuss safe connection of oscilloscope to mains. The current transformer appropriately terminated will be ok. Differential voltage probes are great (but relatively expensive, unless you land one second-hand). You can use a voltage transformer to keep voltage measurement simple, but won't be super-accurate for observing some of the transient events. Battery powered oscilloscopes from Fluke are purpose-made, but they are really expensive, even for really old ones.

7

Other Equipment & Products / Re: Three most useful tools I got from AliExpress

« Last post by watchmaker on Today at 09:40:16 pm »

Links to the tools please. 

The board holder does look very nice, and do I see you invested in a chip tester? The one Adrian Black (digital basement) used to test al kinds of chips with?

I really like the board holder.    If a board is too long, you can always hold it sideways or buy an Aluminum bar at a metals supplier.

Yes, I am assembling the retrochip tester from 8bit-museum.de.  I found it is much cheaper (but more painful) to order the parts from DigiKey; $120 vs about $250.

Per Request:

https://www.aliexpress.us/item/3256806317632603.html

https://www.aliexpress.us/item/2255800993178532.html

I have to find the ProsKit desolder gun.  But it was about $100; bought it as a "first timer" on another account.  (Yes, I am that cheap!)

8

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

« Last post by tatel on Today at 09:39:59 pm »

It is certainly doable. My previous comment wasn't an endorsement of western safety standards.  In the west we are trending towards finding that a one in a million chance of someone getting a hangnail is unacceptable.  People in the US are currently going crazy over a vacuum thermos that has a lead seal that is not externally accessible, and claiming a billion dollars of emotional damage from being in the airplane that lost a window.

Yeah, after Fukushima all that hype about western secure designs is now clearly understood as BS, one only needs just a functional brain. But, hey, we are winning 3 to 1! Not to mention TMI and those "incidents" while developing the thing because then our advantage would be mostly against de Olympic sport ideals...

9

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

« Last post by NNNI on Today at 09:30:40 pm »

I was just about to bring up the point about being able to upload code via USB. It is very convenient and fast. However, programming via the SWD pins (using a Raspberry Pi debugger, for example) is another alternative. I am not sure how much SWD programming is dependent on system clock.

I am honestly not sure when I will be getting back to the project. I left it in a rather messy state, so getting everything running and familiarizing myself with the code diminddl and I worked on nearly a year ago will take some time, plus I have to finish testing my own ideas first. The project files are available, so it should be possible to get your own set of boards for experimentation, or replicate the core circuit (it's quite simple) on a breadboard. I understand your eagerness for the results, but all I ask for is a little patience till I can get everything sorted on my side.

10

General Technical Chat / Re: Cable Management

« Last post by watchmaker on Today at 09:28:50 pm »