Author Topic: HP 34401a DMM with leaking segments  (Read 14556 times)

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Online qu1ck

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Re: HP 34401a DMM with leaking segments
« Reply #100 on: July 28, 2018, 05:44:43 am »
How about displaying the 1 or 2 extra digits that are available via GPIB or RS232?
Since he is getting data given to front panel i think it is not possible.
Correct. Also what's the point? I didn't know more digits are available on GPIB but they can't be meaningful digits, can they? At given sampling rate front panel already displays every digit of resolution the instrument has.
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Offline coromonadalix

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Re: HP 34401a DMM with leaking segments
« Reply #101 on: July 28, 2018, 06:29:16 am »
Don't get too over complicated  lolll
 

Offline hillflyer

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Re: HP 34401a DMM with leaking segments
« Reply #102 on: July 29, 2018, 07:36:51 am »
I agree with not getting too complicated.
I do think the extra digits provide some meaningful information though.
The graph shows my quiet 2.5V reference on the 10V range of the 34401a.
 

Online qu1ck

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Re: HP 34401a DMM with leaking segments
« Reply #103 on: July 29, 2018, 09:02:03 am »
That's interesting, that looks like 8 digits on 10v range. How can you be sure that isn't just ADC noise?
Either way, I can't do anything about adding those digits, that information is not sent to front panel.
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Offline hillflyer

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Re: HP 34401a DMM with leaking segments
« Reply #104 on: July 30, 2018, 02:49:07 am »
Yeah, no problem. :)
Re. ADC noise: In 6 1/2 digit slow mode, it looks like there is about 2uV p-p noise incl. the reference noise.
I use 5 paralled MAX6325 for lower noise.
I am sure you cannot rely on the long term accuracy of these extra digits, but sometimes it is helpful
to be able to squeeze a bit of extra info out of that measurement if needed...


 

Online qu1ck

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Re: HP 34401a DMM with leaking segments
« Reply #105 on: August 06, 2018, 09:36:46 pm »
Long overdue update. Good news, I didn't screw up :)







Board works perfectly fine. Don't mind the botched wire on the last pic, it's an impatient man's diode.
Nothing is true (as far as measurements go)
and everything is permitted (as long as you are ok with magic smoke escaping)
 
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Offline HighVoltage

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Re: HP 34401a DMM with leaking segments
« Reply #106 on: August 06, 2018, 09:53:26 pm »
Looking really good!
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Offline zucca

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Re: HP 34401a DMM with leaking segments
« Reply #107 on: August 06, 2018, 10:10:13 pm »
Drool!

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Offline coromonadalix

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Re: HP 34401a DMM with leaking segments
« Reply #108 on: August 07, 2018, 07:14:44 am »
drool +1
 

Offline bitseeker

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Re: HP 34401a DMM with leaking segments
« Reply #109 on: August 07, 2018, 01:13:32 pm »
Wow! As Dave would say, "It's like a bought one."
I TEA.
 

Online qu1ck

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Re: HP 34401a DMM with leaking segments
« Reply #110 on: August 07, 2018, 07:03:37 pm »
Testing and implementing display rotation (almost) done:



By the way I have 11 spare boards. 5 from original batch (need a bit of precision scraping of solder mask) and 6 from re-fab. Allpcb fixed their shit, no questions asked. Also both times they sent 6 instead of ordered 5.

I'm going to keep 1 but I will probably send out the rest to interested parties for a symbolic payment that I have yet to think of. Frequent posters of this thread get first dibs.
Nothing is true (as far as measurements go)
and everything is permitted (as long as you are ok with magic smoke escaping)
 

Offline zucca

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Re: HP 34401a DMM with leaking segments
« Reply #111 on: August 07, 2018, 08:03:52 pm »
vote qu1ck for president.

Looks awesome.
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Offline HighVoltage

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Re: HP 34401a DMM with leaking segments
« Reply #112 on: August 07, 2018, 08:15:08 pm »
You did an amazing job with this.
There are 3 kinds of people in this world, those who can count and those who can not.
 

Offline coromonadalix

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Re: HP 34401a DMM with leaking segments
« Reply #113 on: August 07, 2018, 08:51:21 pm »
is it me  it seem very bright ???  would it be possible to dim it a little ???   nice job :)
« Last Edit: August 07, 2018, 08:53:25 pm by coromonadalix »
 

Offline zucca

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Re: HP 34401a DMM with leaking segments
« Reply #114 on: August 07, 2018, 08:56:14 pm »
With the acrylic glass on top it should be just perfect... I would not dim it.

« Last Edit: August 07, 2018, 09:05:16 pm by zucca »
Can't know what you don't love. St. Augustine
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Online qu1ck

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Re: HP 34401a DMM with leaking segments
« Reply #115 on: August 08, 2018, 02:43:00 am »
At some point contrast will be configurable to reduce burn in. But it looks just right on max imo.
Nothing is true (as far as measurements go)
and everything is permitted (as long as you are ok with magic smoke escaping)
 

Offline Detzi

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Re: HP 34401a DMM with leaking segments
« Reply #116 on: August 08, 2018, 05:06:42 am »
thats a really nice mod. I like it, great work!  :clap:  But will the OLED not have the tendency to burn in ?
« Last Edit: August 08, 2018, 05:13:51 am by Detzi »
 

Offline free_electron

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Re: HP 34401a DMM with leaking segments
« Reply #117 on: August 08, 2018, 05:43:48 am »
the display is much smaller than the real characters.
i would change the font to be more 7 segment like and scale down the mVDC text.
in essence : get rid of the bargraph : larger numericals , smaller alpha.

otherwise i like it.
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Any comments, or points of view expressed, are my own and not endorsed , induced or compensated by my employer(s).
 

Offline coromonadalix

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Re: HP 34401a DMM with leaking segments
« Reply #118 on: August 08, 2018, 06:13:57 am »
just sad not to find a perfect fit in size  snif,  but job well done, next a fluke 8846a  lolll
 

Offline bitseeker

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Re: HP 34401a DMM with leaking segments
« Reply #119 on: August 08, 2018, 12:36:09 pm »
Looks awesome, qu1ck! And you went from concept to production quite quickly, too (very much in line with your username ;D). I'm definitely interested in a board.

Regarding user-specific preferences for display/font size, etc., qu1ck said he was making the project open source, so you'll be able to modify how it looks and could adapt it to other displays.
I TEA.
 

Online qu1ck

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Re: HP 34401a DMM with leaking segments
« Reply #120 on: August 14, 2018, 08:39:03 pm »
Firmware and hardware is released.

I only have mechanical considerations left to resolve I think. I.e. how to mount the display.
Nothing is true (as far as measurements go)
and everything is permitted (as long as you are ok with magic smoke escaping)
 
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Online qu1ck

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Re: HP 34401a DMM with leaking segments
« Reply #121 on: August 27, 2018, 11:39:12 am »
As luck would have it the metal shroud of the old screen fits new screen pretty much perfectly.
Even existing small flaps that used to hold the glass panel can now hold the display pcb eliminating need for any screws!



On the left the pcb slightly leans on the big fat MCU, in the middle shroud flaps are over it and at the far right end shroud flaps are under it. That creates small tension in pcb which is enough to hold it in place pretty well.



This is how it looks like in the panel:



And the satisfying conclusion to this endeavor:





One thing that is not ideal is the front glass being quite thick requires a usb cable with long connector end, your standard phone cables will not click in.

But while this is a conclusion for the project it's not the end for firmware. I still have not utilized the onboard eeprom, which I plan to store settings in.
Changing contrast on the fly, displaying a label in place of the bar graph, custom fonts and ability to display bigger digits at the expense of bar graph are on my radar.
You can follow the firmware github repo for future updates.
Nothing is true (as far as measurements go)
and everything is permitted (as long as you are ok with magic smoke escaping)
 
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Offline bitseeker

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Re: HP 34401a DMM with leaking segments
« Reply #122 on: August 27, 2018, 11:59:58 am »
Amazing how well all the new bits fit in place. Congrats on a very cool and successful display upgrade.
I TEA.
 

Online mlefe

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Re: HP 34401a DMM with leaking segments
« Reply #123 on: August 27, 2018, 12:10:42 pm »
Excellent work!!  :-+ :clap:
 

Online qu1ck

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Re: HP 34401a DMM with leaking segments
« Reply #124 on: August 27, 2018, 12:15:00 pm »
Thanks

Now I have 10 boards I can send out and 1 mostly working VFD screen :D
Anyone who wants a board can pm me, we will exchange addresses and I will send you a board in exchange for a fridge magnet. I like fridge magnets :)
Doesn't have to be a big one, something that can be send with ordinary mail is fine. if it's connected to your local landmark that would be great, but anything will do.
I don't expect to receive a lot of requests, but in case I do priority will go to users who posted in this thread.
Nothing is true (as far as measurements go)
and everything is permitted (as long as you are ok with magic smoke escaping)
 


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