electro-music.com   Dedicated to experimental electro-acoustic
and electronic music
 
    Front Page  |  Radio
 |  Media  |  Forum  |  Wiki  |  Links
Forum with support of Syndicator RSS
 FAQFAQ   CalendarCalendar   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   LinksLinks
 RegisterRegister   ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in  Chat RoomChat Room 
go to the radio page Live at electro-music.com radio 1 Please visit the chat
poster
 Forum index » DIY Hardware and Software » Thomas Henry designs
Measureing Micro volts? ?
Post new topic   Reply to topic Moderators: Scott Stites
Page 1 of 1 [8 Posts]
View unread posts
View new posts in the last week
Mark the topic unread :: View previous topic :: View next topic
Author Message
Wobuse



Joined: Dec 07, 2011
Posts: 34
Location: Lyons,il

PostPosted: Tue May 14, 2013 5:54 pm    Post subject: Measureing Micro volts? ?
Subject description: Matching NPNs for the T.Henry VCO 1
Reply with quote  Mark this post and the followings unread

I built Ian Fritz's transistor matching circuit ,and it seems to work great 'cept my meters only go down to .1 mV....
I think I need to go down to uV,to really get tight pairs .
What are your recommendations for meters that can go so low.
Thanks; in advance.

_________________
"It's nice 2 B important; but it's important 2 B nice"

Visit my studio ; LimeStoneLabs at: www.Facebook.com/LSlabs
Hear some of my sound track work ,on the web series ,, www.cafegangster.com/16
https://soundcloud.com/james-phillips-75
Back to top
View user's profile Send private message Visit poster's website
fonik



Joined: Jun 07, 2006
Posts: 3950
Location: Germany
Audio files: 23

PostPosted: Thu May 23, 2013 2:30 am    Post subject: Reply with quote  Mark this post and the followings unread

AFAIK matching below 2mV is good enough!? i read it somewhere, i just can't recall...
_________________
Posted Image, might have been reduced in size. Click Image to view fullscreen.
cheers,
matthias
____________
Big Boss at fonitronik
Tech Buddy at Random*Source
Back to top
View user's profile Send private message Send e-mail Visit poster's website
fonik



Joined: Jun 07, 2006
Posts: 3950
Location: Germany
Audio files: 23

PostPosted: Thu May 23, 2013 2:48 am    Post subject: Reply with quote  Mark this post and the followings unread

okay, i found it: in the minimoog service manual robert moog recommended +/-2mV for the VCO's NPN pair.
however, the 1st pair in a CA3086 is matched to less than 1mV, the pair in a LM394 is matched to 50μV.

_________________
Posted Image, might have been reduced in size. Click Image to view fullscreen.
cheers,
matthias
____________
Big Boss at fonitronik
Tech Buddy at Random*Source
Back to top
View user's profile Send private message Send e-mail Visit poster's website
Wobuse



Joined: Dec 07, 2011
Posts: 34
Location: Lyons,il

PostPosted: Thu May 23, 2013 6:16 am    Post subject: Reply with quote  Mark this post and the followings unread

fonik wrote:
okay, i found it: in the minimoog service manual robert moog recommended +/-2mV for the VCO's NPN pair.
however, the 1st pair in a CA3086 is matched to less than 1mV, the pair in a LM394 is matched to 50μV.

Thanks Fonik..
I put a follow up post here..http://electro-music.com/forum/topic-58135.html

_________________
"It's nice 2 B important; but it's important 2 B nice"

Visit my studio ; LimeStoneLabs at: www.Facebook.com/LSlabs
Hear some of my sound track work ,on the web series ,, www.cafegangster.com/16
https://soundcloud.com/james-phillips-75
Back to top
View user's profile Send private message Visit poster's website
marvkaye



Joined: Mar 14, 2011
Posts: 225
Location: Fla

PostPosted: Fri May 24, 2013 7:57 am    Post subject: Reply with quote  Mark this post and the followings unread

I've been matching transistors using the Ian Fritz circuit to +/- 50 uV using a 50,000 count BK Precision bench meter, but recently added to my meter collection with a Keithly 177 digital microvolt meter which is accurate to +/- 2uV. Picked it up on Ebay for under $100 including shipping, and have seen them there since my purchase for considerably less (of course... Rolling Eyes ) Lots of meters out there today, though, that are accurate to the microvolt, just look around.

Most of the matching articles suggest that trannies are matched when they're +/- 2 mV Vbe, though, which is an order of magnitude less precise than what I've been trying to hold. Like most folks have mentioned, you can get within 1-2mV just by picking trannies from the same batch. Lots has changed in semi manufacturing since those early Moog days, that's for sure.

FWIW.........

<marv>
Back to top
View user's profile Send private message
Wobuse



Joined: Dec 07, 2011
Posts: 34
Location: Lyons,il

PostPosted: Fri May 24, 2013 11:13 pm    Post subject: Reply with quote  Mark this post and the followings unread

marvkaye wrote:
I've been matching transistors using the Ian Fritz circuit to +/- 50 uV using a 50,000 count BK Precision bench meter, but recently added to my meter collection with a Keithly 177 digital microvolt meter which is accurate to +/- 2uV. Picked it up on Ebay for under $100 including shipping, and have seen them there since my purchase for considerably less (of course... Rolling Eyes ) Lots of meters out there today, though, that are accurate to the microvolt, just look around.

Most of the matching articles suggest that trannies are matched when they're +/- 2 mV Vbe, though, which is an order of magnitude less precise than what I've been trying to hold. Like most folks have mentioned, you can get within 1-2mV just by picking trannies from the same batch. Lots has changed in semi manufacturing since those early Moog days, that's for sure.

FWIW.........
<marv>


I did pick up a better meter... Check the link in my reply to Fonik.
I think I need to rework that test circuit though ,because , at the time I only had a 100k trim ,so I used that for one side & a resistor on the other.I can match the ohmage out to .000, but that's not good enough..
I need to use two resistors and a low ohm multi turn trim ,(like Ian suggested)so I can completely null the circuit ,and eliminate all the error, which I haven't been able to do,in my current set up.
Any tips for finding those super matched pairs?Is there a particular:manufacture you favor? transformer

_________________
"It's nice 2 B important; but it's important 2 B nice"

Visit my studio ; LimeStoneLabs at: www.Facebook.com/LSlabs
Hear some of my sound track work ,on the web series ,, www.cafegangster.com/16
https://soundcloud.com/james-phillips-75
Back to top
View user's profile Send private message Visit poster's website
marvkaye



Joined: Mar 14, 2011
Posts: 225
Location: Fla

PostPosted: Sat May 25, 2013 8:11 pm    Post subject: Reply with quote  Mark this post and the followings unread

I bought a couple of these Vishay/Dale 0.01% 15ppm resistors for the matched pair in a wheatstone bridge circuit to use for matching other resistors for R/2R ladders. A 50 ohm trimmer in series with the smaller valued one got them as close to identical as I could measure them using a uCurrent box. This, BTW, is way overkill for matching transistors, IMHO. There's a better way to use Ian's circuit that is much simpler. Put any transistor of the type you're trying to match in one of the sockets and just leave it there as a standard. Put your next transistor to match in the other socket (call it the DUT socket), let it settle down and note the difference in Vbe. Using a plastic parts box with 36 compartments as a sorter put that first DUT transistor into one of the central bins and note its Vbe difference on a bin chart stuck to the inside of the lid. Put another transistor into the DUT socket and repeat the test... note its difference and assign it to a bin relative to the first one. Keep going until you have multiple transistors in various bins... trannies with the same difference in Vbe from the standard match each other. This is much quicker than siwtching emitters, working out math problems, or even worrying about whether or not your resistor pair is close enough. Try it, I think you'll like it.

<marv>
Back to top
View user's profile Send private message
fonik



Joined: Jun 07, 2006
Posts: 3950
Location: Germany
Audio files: 23

PostPosted: Sun May 26, 2013 2:52 pm    Post subject: Reply with quote  Mark this post and the followings unread

good point, marv. simplicity is beautiful Very Happy
_________________
Posted Image, might have been reduced in size. Click Image to view fullscreen.
cheers,
matthias
____________
Big Boss at fonitronik
Tech Buddy at Random*Source
Back to top
View user's profile Send private message Send e-mail Visit poster's website
Display posts from previous:   
Post new topic   Reply to topic Moderators: Scott Stites
Page 1 of 1 [8 Posts]
View unread posts
View new posts in the last week
Mark the topic unread :: View previous topic :: View next topic
 Forum index » DIY Hardware and Software » Thomas Henry designs
Jump to:  

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum


Forum with support of Syndicator RSS
Powered by phpBB © 2001, 2005 phpBB Group
Copyright © 2003 through 2009 by electro-music.com - Conditions Of Use