Recent Posts

1

Beginners / Re: Kits/Projects for advancing beginners???

« Last post by RoGeorge on Today at 06:24:43 am »

Another type of kit, which is more for learning than for building, is ADALM2000 (with letter M before 2000, the all-in-one measuring instrument and signal generator) + its components kit ADALP2000 (with letter P before 2000), a collection of most used parts and integrated circuits.

Its goal is to teach the student about analog electronic, with brief theory then by building and measuring the circuit on a breadboard.  Sure, one can follow the classes and use other measuring instruments instead of ADALM2000+ADALP2000.  Using own instruments to generate the signal then measure the results might also be a good exercise in learning own oscilloscope/generator/supply/DMM/etc.

The lessons can be found in the "student zone" https://www.analog.com/en/resources/analog-dialogue/studentzone/studentzone-september-2024.html they are prepared by engineers from Analog Design, and to give a random example, this is the latest one:

ADALM2000 Activity: Envelope Detector
https://www.analog.com/en/resources/analog-dialogue/studentzone/studentzone-september-2024.html

2

Repair / Re: Agilent 34401A Bubble on PCB ... can it be saved ?

« Last post by Kleinstein on Today at 06:23:16 am »

The current is rather far off, well more than expected for leakage at Q211 or Q202 or the OP-amp bias current. The transistors in the protection would not effect the low current, even if bad or broken.
A point could be if the OP-amp is genuine or a Ebay/Ali part.

The change in current from doing the extra cleaning step points strongly towards a dirt problem, though it could still also be a thermal effect (e.g. higher temperature in the 2nd test).
No need for a full warm up test. The first half hour should show most of the thermal effect.

Contact cleaner may or may not be suitable, as some include lubricants and can leave a resudue. They may also not be good solvents, but more a thing to remove oxide layers. A spray can can also contaminate other areas from splatter. HIgh pressure is more a thing for cleaning a whole board, not so much for loacal claning. That is more a thing for brush, seringe and tissue.

One can still use IPA or similar around / under the chips. It will flow also under the chip and can be sucked out / wicked out with clean tissue. The dirt is removed by the solvent removed, not by the solvent added.

IPA is also only good for some contaminations and there are different purities / grades. More salt like contaminations are better removed with water or a IPA / water mix. More organic / grease like dirt would want high purity / low water content IPA or even a different solvent. It may well need multiple cleaning steps. Usually water or a water+IPA mix first and at the end clean IPA.

One could try / test cleaning of flux residue on a different PCB. So do experiments separate first, to see what works with the flux that was used in the repair. For the flux the soldering step can change things - heated flux is different from fresh or only partially heated. Not all residue from the flux is actually bad - some contain some parafin / wax component, that is hard to remove, but isolating.

3

Test Equipment / Re: What does "Average Type" Refer To in Siglent SVA1032X "BW" Menu ???

« Last post by rf-loop on Today at 06:18:04 am »

Hopefully, this old famous and widely known paper is familiar to everyone who is a little more serious about spectrum analyzers.
Throughout history, this paper has had its own versions, starting way back in the days of HP. The current version is quite relevant with modern analyzers. Siglent also pretty much follows the same principles.
You should really read the paper and not just skim through it. Including the song where we talk about noises and yes, things related to avareage modes come up there as well... more directly and indirectly.

Paperi is of course: Latest Keysight version; Spectrum Analysis Basics (AN150)

https://www.keysight.com/gb/en/assets/7018-06714/application-notes/5952-0292.pdf

4

Beginners / Re: current sense chip: will it work?

« Last post by skeeterweazel on Today at 06:17:24 am »

Here is a circuit idea. The current sensor is not pass through so you don't need to deal with the high currents through your PCB. Insteead attach it to a high current wire in the proper orientation with cables ties or something similar. The board has three wires, two for supply (3.3V or 5V) and one for digital output (high when active). I didn't not include bypass capacitors on the power rails.

The operation of a comparator is very simple. Its output is VDD when the positive input is higher than the negative (even a little bit) and GND otherwise.  The circuit includes a low pass filter that is recommended in the datasheet and a feedback resistor for some hysteresis.

I'm liking this the more i look at it. Could you point me in the direction of an explanation of the circuit?
Can the sensing chips be "over powered" with too many amps? I'm looking to only sense the first amp, but wire may have more than 10 amps at times. Does that hurt the chip?
Thx.
Marty

5

Projects, Designs, and Technical Stuff / Re: Relatively high voltage precision DAC amplification

« Last post by Salitronic on Today at 06:15:46 am »

You could consider a cascaded amplifier configuration such as this: https://www.researchgate.net/publication/283661284_A_Cascaded_Linear_High-Voltage_Amplifier_Circuit_for_Dielectric_Measurement
and scale it to your required voltage range.

I have designed similar cascaded systems for high voltage (kV) signal generation but typically using cascaded H-bridge (switch-mode) converters which is not suitable for your very low noise requirement. It is a very convenient design topology as you have to deal with multiple modules but each one at a low voltage. Power is also split among all modules making thermal management a lot easier. Obviously it is a complex design with multiple modules each requiring independent isolation and synchronized control of all modules.

6

Test Equipment / Re: Test Equipment Anonymous (TEA) group therapy thread

« Last post by wkb on Today at 06:15:05 am »

What is a non-inverting inverter?  Is it an ordinary buffer?  Or is it what engineers call the Signetics don't gate?

It is from the Illogical IC family of which for example the Exclusive Maybe Gate and the Never Gate are also members.

In other words "Its dead Jim".

7

Beginners / Help selecting a capacitor to fix power drop out issue

« Last post by RickAbraham on Today at 06:11:43 am »

Hi guys,
I have a 10.1 inch LCD screen in my car, it runs off 5V and approx 900mA draw.
I turn the screen on by sending power to it and turn it off my cutting power to it.
When the screen is powered on and I use other functions in the car that have a high amp draw such as the starter motor and windscreen wiper motor it causes
the screen to shut off for a second or two before it comes back on.
Must be very sensitive to slight voltage drop.
I am thinking about wiring in a capacitor to stabilize the power feed to the screen to prevent the cutouts, but I do not know what size capacitor I require.
When I power the screen off I do not want it staying on for any longer than approx 15 seconds running off the capacitor.

Can I please have help in selecting an appropriately sized capacitor for my project. 

8

Test Equipment / Re: Tektronix 2465B oscilloscope teardown

« Last post by calibrationfixture on Today at 06:08:39 am »

I think once a saw a listing for a BO7xxx something.

Hi,

Maybe you saw a H70xxxx (Heerenveen) listing. My latest production 24xxB Scope is a 2455B (J301046) with parts dated 9434 (year 1994, week 34) etc. Last Product Catalog in which 24xxB's are listed is 1995.

Calibrationfixture

9

Buy/Sell/Wanted / Re: SALE (World): Rigol DHO-804 Oscilloscope

« Last post by Nominal Animal on Today at 06:06:31 am »

(I didn't notice that you can actually see the embossed "Rigol" on the back, and the "Rigol" logo in an oblique angle in the image showing someone holding the scope.  Apologies.)

It seems more likely to me that these are original Rigol-made scopes, but from some grey channels -- factory rejects or customer returns maybe, or units that are not meant to be sold internationally.

Fully agreed.

I would not buy one of these since I would be concerned about product quality and warranty, and would certainly not expect to get warranty or support from Rigol directly.

Exactly.

If one isn't careful, it is very easy to get caught by this kind of an ad.  While we can only guess as to the reason, there must be a reason Banggood did at least attempt to remove any mention of "Rigol", so much so to edit the main product picture.  It stinks of risk to me.  For something like this, I'm not sure the mediocre price saving is worth the risk, but everyone chooses their own risk thresholds of course.

(I just see people getting caught by this kind of "fudging", especially with open source software –– blaming the developers, and not the vendor/provider who provided the software to you with an implied promise of some sort of support –– so I want people to be sharper.  Here, it is clear that very few would actually know to blame Banggood for any issues with the scope, and would instead blame Rigol.  [Same with software licenses, especially with Qt.  No, you don't need a commercial license to use most of Qt in a proprietary product; only if you use certain extensions/modules, or need to modify the Qt libraries themselves to work for you.]  It can be exhausting to try and explain the details to people who are not used to reading stuff carefully, and just breeze through.)

10

Test Equipment / Re: SDS800X HD Bug Reports + Firmware

« Last post by eTobey on Today at 06:06:22 am »

Wtf is this? Another issues appeared! The trigger is odd. When the level is at 151V, it triggers just fine on a 3.3V level pulse! Something must have crashed in the software, without an obvious sign.
https://youtu.be/22_viJaxcTI
https://youtu.be/99HdnPxrwTo

EDIT:
Issue dissapeared after restart. Scacle and position (maybe more?) of the problem channel changed though.

I tried.

Channel 1 was set at 10x probe and 5V/div, 13V offset . Trigger set to pulse, negative. 1ms timeout. 1MPts, 20ms/div, time delay 1.25s, 5 MSa/s. 4 CH used.

I cannot reproduce (with data you published) neither 151V trig level (you cannot enter more than 7,5V with knob or keyboard) and Pulse-> Trigger level works normally.

If the user cant enter more than 7.5V trigger level, but the picture shows 151V, then it can be classified as a bug?