Author Topic: Test Equipment Anonymous (TEA) group therapy thread  (Read 3646698 times)

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Offline Kosmic

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72675 on: October 20, 2020, 01:07:14 pm »
Cheap General Radio 1644A Megohm meter on ebay this morning.

https://www.ebay.com/itm/174486494802?ul_noapp=true

 
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Offline mnementh

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72676 on: October 20, 2020, 02:17:09 pm »
In related events... Canadian coathangers are too fukkin' good.  :wtf:

I'm right now on coathanger number 7 (7 coil segments like in the wet load above) and still drawing way too much current; the steel wire is too damned fat! The cheap 'merkin coathangers above are nice & thin... only needed 4 to get loading right where I wanted. :-DD

mnem
Every silver lining has its grey cloud.

You need to remember that where Americans use 480 volts, we use 600 up here.  That in turn mandates the heavier coat hangers in order to handle the higher power dissipation requirements.


mnem


It was the delivery... For some reason, I heard that in my grand-dad's perfect deadpan southern drawl, and felt the unflinching gaze with which he delivered all tidings both good and bad, and it was a perfect moment.

Yeah, I know that came as much from what was inside of me as what was delivered by all those inconvenienced electrons; but it doesn't matter. For a moment the old man reached out to me across space and time, and he was here with me, and it was good.

Thank you, my friend.

mnem
*wistful sigh*
 

Offline battlecoder

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72677 on: October 20, 2020, 02:31:11 pm »
You will never get the last digit to sit on 0 during calibration. It's inherent in the design of most digital systems that the least significanrt bit will flip between 0 and 1. For a counter it depends on when the input signal switches compared to the counting gate in the counter (noise on the level trigger also contributes but is more noticable on high precision countes). The only way you will get a consistent zero is if the internal oscillator and the signal you are measuring are phase locked, but then you are not actually checking the accuracy of the internal oscillator.
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Offline tggzzz

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72678 on: October 20, 2020, 02:34:21 pm »
Here is to be to be peaceful and orderly. Without bad smell due to my old crappy smoke extractor. Now its a covid proof fart extractor?

#1 rule to limit test gear damage: Limit coffee movement, hold coffee in stainless steel screwable mug. Always.

OK, I give up. What exactly are you trying to show in these pictures?  :-//

And I thought my phone took shitty pictures.  ::)

Have a look at the threads he has started, e.g. https://www.eevblog.com/forum/testgear/feel-bad-about-my-siglent-purchase/ or https://www.eevblog.com/forum/repair/pre-emptive-capacitor-change-on-beloved-laptop/msg3284796/#msg3284796
« Last Edit: October 20, 2020, 02:38:22 pm by tggzzz »
There are lies, damned lies, statistics - and ADC/DAC specs.
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Online med6753

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72679 on: October 20, 2020, 02:36:33 pm »
Here is to be to be peaceful and orderly. Without bad smell due to my old crappy smoke extractor. Now its a covid proof fart extractor?

#1 rule to limit test gear damage: Limit coffee movement, hold coffee in stainless steel screwable mug. Always.

OK, I give up. What exactly are you trying to show in these pictures?  :-//

And I thought my phone took shitty pictures.  ::)

Have a look at the threads he has started.

I have.  :palm:
An old gray beard with an attitude.
 

Offline Microdoser

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72680 on: October 20, 2020, 02:38:22 pm »


$31 or $37 W/Comms at bang-em-good

I'm just gonna leave this here where anybody might trip over it...

mnem
 >:D

I have one of those. Powered it via an old ATX power supply (visible just behind) boosted from 12V-55V with another AliExpress item which is then buck converted by the DPS 5005 into 0-50V, 0-5A (at 50V it will only manage 4A but I have never needed voltage or amps that high for anything). Not bad, although for some circuits it fails to regulate voltage. It has done well for the price, but I am on the lookout for a proper bench power supply. Handy to have a graph of power usage on the tablet connected via bluetooth.

[attach=1]
 

Offline Wolfgang

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72681 on: October 20, 2020, 02:42:16 pm »


$31 or $37 W/Comms at bang-em-good

I'm just gonna leave this here where anybody might trip over it...

mnem
 >:D

I have one of those. Powered it via an old ATX power supply (visible just behind) boosted from 12V-55V with another AliExpress item which is then buck converted by the DPS 5005 into 0-50V, 0-5A (at 50V it will only manage 4A but I have never needed voltage or amps that high for anything). Not bad, although for some circuits it fails to regulate voltage. It has done well for the price, but I am on the lookout for a proper bench power supply. Handy to have a graph of power usage on the tablet connected via bluetooth.

[attach=1]

I do know that all this is incredibly cheap compared to *real* lab supplies, but I would be afraid that it would jam all my measurements with incredible amounts of RFI. Any experiences ?
 

Online BravoV

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72682 on: October 20, 2020, 02:44:20 pm »


$31 or $37 W/Comms at bang-em-good

I'm just gonna leave this here where anybody might trip over it...

mnem
 >:D

I have one of those. Powered it via an old ATX power supply (visible just behind) boosted from 12V-55V with another AliExpress item which is then buck converted by the DPS 5005 into 0-50V, 0-5A (at 50V it will only manage 4A but I have never needed voltage or amps that high for anything). Not bad, although for some circuits it fails to regulate voltage. It has done well for the price, but I am on the lookout for a proper bench power supply. Handy to have a graph of power usage on the tablet connected via bluetooth.

[attach=1]

I do know that all this is incredibly cheap compared to *real* lab supplies, but I would be afraid that it would jam all my measurements with incredible amounts of RFI. Any experiences ?

Dave did review and measured it.

Offline bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72683 on: October 20, 2020, 02:47:42 pm »
Hmm. With all these things I'm less worried about the behaviour when it is working than the behaviour when it is transitioning from working to not working at some point. That requires objectivity and analysis of the design and possible failure modes. This is a potentially huge part of the development cost of a product which is not being reaped back at that price so it probably hasn't been done. Thus, it's a risk.

Also, a bluetooth interface on a power supply? That can fuck right off into the stupid bin. If we can't write software for medical devices and sex toys that don't do you physical harm (google it) when they go wrong then we can't write software for a power supply that'll not burn your house down remotely :)
« Last Edit: October 20, 2020, 02:49:30 pm by bd139 »
 

Offline BU508A

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72684 on: October 20, 2020, 02:52:49 pm »
Not the same module but similar:

The Signal Path #112 - Noise & Performance Considerations of the DPH3205 Buck-Boost DC/DC Converter Module



Edit:

Here are the videos from Dave:

EEVblog #1030 - $20 DIY Bench Power Supply!




EEVblog #1035 - Flaming DIY Power Supply!


« Last Edit: October 20, 2020, 03:01:08 pm by BU508A »
“Chaos is found in greatest abundance wherever order is being sought. It always defeats order, because it is better organized.”            - Terry Pratchett -
 

Online med6753

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72685 on: October 20, 2020, 02:55:57 pm »
So one of my Fluke 8800A's needs a minor repair. The 200mV/200 ohm range LED is intermittent. Sometimes comes on, sometimes doesn't, and even sometimes randomly flashes. So today I figured I'd pull it apart and see what's up.

Wouldn't you know it. The manual that I have is complete EXCEPT for the schematic of the display panel.  :wtf: :palm: So off to Artek Manuals and pay the $8 USD for a download. At least I know it will be a good copy and complete. But they "lock down" their PDF's and you can't copy/paste pages or portions of pages and drop into a separate file. Oh well.  :-//     
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Offline mnementh

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72686 on: October 20, 2020, 02:58:51 pm »
   $31 or $37 W/Comms at bang-em-good

I'm just gonna leave this here where anybody might trip over it...

mnem
 >:D
I had the version without connectivity and it worked fine. And a few months ago I upgraded to the one with USB comm (not a fan of the BT option. That module plus the SMPS that powers it contribute with enough electromagnetic pollution on their own already). Works fine, but the noise/ripple levels are a bit on the high side. Definitely not something I'd use without filter caps if I'm working with a voltage (or noise) sensitive circuit, but it's great to have a cheap power supply that has a decent voltage/current range and can be controlled from the PC.


I know... I have its cousin here on the corner of my bench, and it is a surprisingly capable little beast. Because I used XT-60s, I have all kinds of adapters already made up for my RC toys... or I can quickly fab up something custom on the spot if I need it. :-+

But that post was me needling Specmaster over his tribulations with that PL310; it was a backhanded suggestion as to how he could make all that misery just go away.  ;)

Of course, Spec did not take the bait.  :-DD

mnem
 :popcorn:
« Last Edit: October 20, 2020, 03:01:09 pm by mnementh »
 
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Offline Microdoser

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72687 on: October 20, 2020, 03:05:19 pm »


$31 or $37 W/Comms at bang-em-good

I'm just gonna leave this here where anybody might trip over it...

mnem
 >:D

I have one of those. Powered it via an old ATX power supply (visible just behind) boosted from 12V-55V with another AliExpress item which is then buck converted by the DPS 5005 into 0-50V, 0-5A (at 50V it will only manage 4A but I have never needed voltage or amps that high for anything). Not bad, although for some circuits it fails to regulate voltage. It has done well for the price, but I am on the lookout for a proper bench power supply. Handy to have a graph of power usage on the tablet connected via bluetooth.

[attach=1]

I do know that all this is incredibly cheap compared to *real* lab supplies, but I would be afraid that it would jam all my measurements with incredible amounts of RFI. Any experiences ?

Yeah, quite noisy and has been said above, I would not use it for anything sensitive but if you have nothing else, and a spare ATX power supply kicking about, it is better than nothing.

Easy to connect and use though, and seems accurate enough for what it is. I found it handy for example to connect unknown LED strips salvaged from random equipment then ramp up the voltage until they light to get an idea of what to run them at. In such a case it can limit voltage and current so you can be sure nothing blows up. I have also used it to display power usage, for an example figuring out max current draw for a raspberry pi + screen.

I very quickly though gained the opinion that I really need a proper bench power supply.

Here is a view of some of the noise:

[attach=1]
 

Offline bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72688 on: October 20, 2020, 03:06:51 pm »
But that post was me needling Specmaster over his tribulations with that PL310; it was a backhanded suggestion as to how he could make all that misery just go away.  ;)

Of course, Spec did not take the bait.  :-DD

That's because he knows the fight is worth it and the noise floor is not :)
 
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Offline BU508A

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72689 on: October 20, 2020, 03:07:24 pm »
So one of my Fluke 8800A's needs a minor repair. The 200mV/200 ohm range LED is intermittent. Sometimes comes on, sometimes doesn't, and even sometimes randomly flashes. So today I figured I'd pull it apart and see what's up.

Wouldn't you know it. The manual that I have is complete EXCEPT for the schematic of the display panel.  :wtf: :palm: So off to Artek Manuals and pay the $8 USD for a download. At least I know it will be a good copy and complete. But they "lock down" their PDF's and you can't copy/paste pages or portions of pages and drop into a separate file. Oh well.  :-//   

Perhaps this can help you:

https://www.wikihow.com/Unlock-a-Secure-PDF-File
“Chaos is found in greatest abundance wherever order is being sought. It always defeats order, because it is better organized.”            - Terry Pratchett -
 

Offline mnementh

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72690 on: October 20, 2020, 03:26:29 pm »
But that post was me needling Specmaster over his tribulations with that PL310; it was a backhanded suggestion as to how he could make all that misery just go away.  ;)

Of course, Spec did not take the bait.  :-DD
That's because he knows the fight is worth it and the noise floor is not :)

That energy might be better spent turning that one into a cheap battery charger and getting a proper lab supply>:D



mnem
 

Offline mnementh

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72691 on: October 20, 2020, 03:30:03 pm »
So one of my Fluke 8800A's needs a minor repair. The 200mV/200 ohm range LED is intermittent. Sometimes comes on, sometimes doesn't, and even sometimes randomly flashes. So today I figured I'd pull it apart and see what's up.

Wouldn't you know it. The manual that I have is complete EXCEPT for the schematic of the display panel.  :wtf: :palm: So off to Artek Manuals and pay the $8 USD for a download. At least I know it will be a good copy and complete. But they "lock down" their PDF's and you can't copy/paste pages or portions of pages and drop into a separate file. Oh well.  :-//   

Perhaps this can help you:

https://www.wikihow.com/Unlock-a-Secure-PDF-File

You can also get very usable results using the snipping tool to screencap directly from your .pdf viewer.

mnem
 :-/O
 

Offline mnementh

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72692 on: October 20, 2020, 03:43:30 pm »
Not the same module but similar:

The Signal Path #112 - Noise & Performance Considerations of the DPH3205 Buck-Boost DC/DC Converter Module



Edit:

Here are the videos from Dave:

EEVblog #1030 - $20 DIY Bench Power Supply!




EEVblog #1035 - Flaming DIY Power Supply!


Dave did a followup video on the flaming PSU... his supplier did a thorough investigation and found that the assembly process was overheating those MLCCs, causing them to fracture during manufacture. He stepped up and provided warranty, and revised the design to fix the problem.

Also, to be clear, NOT the same device as 5005, which in fact has a pretty good track record.

The noise "issues" many of these videos show are mostly caused by feeding them with a noisy SMPS (or in one case, picking up unrelated common-mode noise from nearby LED illumination); these modules just amplify that noise. Other vids I've seen show that powered from a reasonably clean linear source and building in a metal box, that noise is greatly reduced. Like with all these "modular electronic gimcracks from China", results are as much dependent upon the user application as the device itself.

Also, obviously, expecting lab-grade power from a $20 module is simply ridiculous on the face of it. :-//

These things have their place, even on a lab workbench, as long as you are mindful of their limitations. 30-50mV noise factor is very usable; bang/buck is still off the hook. :P

mnem
*punt*
« Last Edit: October 20, 2020, 03:57:03 pm by mnementh »
 

Offline bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72693 on: October 20, 2020, 03:48:01 pm »
But that post was me needling Specmaster over his tribulations with that PL310; it was a backhanded suggestion as to how he could make all that misery just go away.  ;)

Of course, Spec did not take the bait.  :-DD
That's because he knows the fight is worth it and the noise floor is not :)

That energy might be better spent turning that one into a cheap battery charger and getting a proper lab supply>:D



Now that's more like it  :-DD
 
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Offline bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72694 on: October 20, 2020, 03:49:08 pm »
So one of my Fluke 8800A's needs a minor repair. The 200mV/200 ohm range LED is intermittent. Sometimes comes on, sometimes doesn't, and even sometimes randomly flashes. So today I figured I'd pull it apart and see what's up.

Wouldn't you know it. The manual that I have is complete EXCEPT for the schematic of the display panel.  :wtf: :palm: So off to Artek Manuals and pay the $8 USD for a download. At least I know it will be a good copy and complete. But they "lock down" their PDF's and you can't copy/paste pages or portions of pages and drop into a separate file. Oh well.  :-//   

Perhaps this can help you:

https://www.wikihow.com/Unlock-a-Secure-PDF-File

There's an easier way if you have chrome. Open the PDF in chrome then do a Save to PDF thus proving that soft security controls are fucking stupid :-DD

(I am having this argument with someone at the moment who wants everything covered but went purple when I suggested I'd just take a picture of the screen with my phone  :-DD)
 

Offline tggzzz

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72695 on: October 20, 2020, 03:53:00 pm »
(I am having this argument with someone at the moment who wants everything covered but went purple when I suggested I'd just take a picture of the screen with my phone  :-DD)

Not a bad example of the old dictum: if you think encryption will solve your problem then you don't understand encryption and you don't understand your problem.
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
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Offline mnementh

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72696 on: October 20, 2020, 03:55:10 pm »


mnem
 :horse:
 

Offline bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72697 on: October 20, 2020, 04:10:15 pm »
(I am having this argument with someone at the moment who wants everything covered but went purple when I suggested I'd just take a picture of the screen with my phone  :-DD)

Not a bad example of the old dictum: if you think encryption will solve your problem then you don't understand encryption and you don't understand your problem.

There's another layer to that which has appeared recently: If you think decryption will solve your problem then you don't understand encryption and you don't understand your problem.

So someone wants to MITM all TLS traffic because they don't trust humans. They forget that it increases the risk ten-fold for legitimate traffic and by the time the event has occurred, the data has been exfiltrated anyway and lastly that the entire system is flawed when it comes to information classification anyway. I suggested they fixed the latter but that means an ego needs to be kicked.

Officially not my funeral soon so I'm speaking my mind quite a lot  :-DD
« Last Edit: October 20, 2020, 04:11:59 pm by bd139 »
 
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Offline Wolfgang

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72698 on: October 20, 2020, 04:21:17 pm »


$31 or $37 W/Comms at bang-em-good

I'm just gonna leave this here where anybody might trip over it...

mnem
 >:D

I have one of those. Powered it via an old ATX power supply (visible just behind) boosted from 12V-55V with another AliExpress item which is then buck converted by the DPS 5005 into 0-50V, 0-5A (at 50V it will only manage 4A but I have never needed voltage or amps that high for anything). Not bad, although for some circuits it fails to regulate voltage. It has done well for the price, but I am on the lookout for a proper bench power supply. Handy to have a graph of power usage on the tablet connected via bluetooth.

[attach=1]

I do know that all this is incredibly cheap compared to *real* lab supplies, but I would be afraid that it would jam all my measurements with incredible amounts of RFI. Any experiences ?

Yeah, quite noisy and has been said above, I would not use it for anything sensitive but if you have nothing else, and a spare ATX power supply kicking about, it is better than nothing.

Easy to connect and use though, and seems accurate enough for what it is. I found it handy for example to connect unknown LED strips salvaged from random equipment then ramp up the voltage until they light to get an idea of what to run them at. In such a case it can limit voltage and current so you can be sure nothing blows up. I have also used it to display power usage, for an example figuring out max current draw for a raspberry pi + screen.

I very quickly though gained the opinion that I really need a proper bench power supply.

Here is a view of some of the noise:

[attach=1]

Yuck. Anyway, its good enough to heat something, drive motors or charge batteries.  8)
 

Offline Cerebus

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #72699 on: October 20, 2020, 04:28:39 pm »
(I am having this argument with someone at the moment who wants everything covered but went purple when I suggested I'd just take a picture of the screen with my phone  :-DD)

Not a bad example of the old dictum: if you think encryption will solve your problem then you don't understand encryption and you don't understand your problem.

The only way to combat this scenario, that I have seen used in practice, was figured out in the 1970s in Multics. You attach security labels to all your files, you attach security labels to all your terminals, someone who logs into one of those terminals gets their security labels (and of processes they run) downgraded to those of the terminal. Try and display a 'secret' document on a 'restricted' terminal - system stops you (and logs it). If you have 'secret' graded terminals you put them in a room with an ugly, uncompromising guard outside who relieves you of any cameras, notebooks etc. and strip searches you on the way out to check that you haven't found a way to write the recipe for Kentucky Fried Chicken down the inside of your thigh.

Security is, first and foremost, a people problem and always will be; attempts to solve it with just computer technology will fail. Encryption is only ever good for ensuring that stuff is secure when it's being transported through, or stored in, somewhere that isn't secure. Proper 'secret' level security is always expensive.
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