Re: [volt-nuts] Making a Reference IC

[Attila Kinali]

今晩は,スタインメツさん、

On Sun, 13 Sep 2015 08:22:29 -0400
Charles Steinmetz  wrote:

> If you replace the op-amp with a modern precision part (I suggest the 
> OPA277 -- others may try to talk you into an auto-zero op-amp, but I 
> think that would be a mistake in this application),


Why would this be a mistake?

Attila Kinali

-- 
Reading can seriously damage your ignorance.
-- unknown
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Re: [volt-nuts] Making a Reference IC

[Poul-Henning Kamp]

In message 
, "Dr. 
David Kirkby (Kirkby Microwave Ltd)" writes:

>A used 3458A fetches several thousand USD, 

There's actually one in france for EUR1500 right now...


-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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Re: [volt-nuts] Making a Reference IC

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 13 Sep 2015 09:15, "M K"  wrote:
> There has been some of those references available second hand from ebay,
mostly pulled, but some may be counterfeit, so look for sellers with
pictures showing it as old..

Several sellers have more than 1, but with one photo, so you would have a
hard time arguing that your board is a fake just because it looks newer
than the photo. I believe it is standard practice to photograph a genuine
article but to ship a fake.

In any case, it is probably possible to make a board look older.

A used 3458A fetches several thousand USD, so I find it hard to believe
that many would be broken for parts. But even if there is a reason 3458As
are being broken up, why are other parts not showing up as often as  the
voltage references?

I just looked on ebay for "3458A board" There are 10, of which 6 are the
voltage reference and the other 4 being various other 3458A boards.
Looking for "3458A PCB" changes it to 6 references and 2 two other PCBs. It
seems a bit suspicious to me that the one board that has wider usage than
the others is available in roughly 2~3 times the quantity of all other
boards put together.

We why don't we see 3458A front panels, power supplies etc,  showing up
much - why all the voltage references?

The fact that there seems to be a market for 3458A reference boards
suggests to me that there would be a market for a voltage reference board
based on the same chip, but designed as a stand alone board.

I can think of a few improvements over a 3458A board.

1) Option to run from batteries to keep it as stable as possible when there
are power failures.

It should also make it possible to ship a board to another volt-nut,
keeping it powered in transit.

I don't know the power consumption of the reference,  and I am aware that
there are some issues shipping batteries,  but these seem much more relaxed
if the battery is inside equipment.

2) Option to run chip at a lower temperature than in a 3458A, as some have
claimed is better.

3) Temperature sensor that recorded min and max temperatures during
shipping.

4) Ability to read time board has been powered on.

I for one would buy such a board, if someone produced one, either as a
blank PCB or populated with components & adjusted. Specialist components
would be more readily available is there was a number wanted.

Dave
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Re: [volt-nuts] Making a Reference IC

[John Phillips]

We upgraded about 20 3458As  to the 4 ppm reference for a local equipment
rental co.
Others may have done the same to and are selling the old boards that may be
even more stable than 4 ppm because they have aged for years.

The difference between references is aging and screening.


On Mon, Sep 14, 2015 at 4:37 AM, Poul-Henning Kamp 
wrote:

> 
> In message  ndcyiggbw_...@mail.gmail.com>, "Dr. David Kirkby (Kirkby Microwave Ltd)"
> writes:
>
> >A used 3458A fetches several thousand USD,
>
> There's actually one in france for EUR1500 right now...
>
>
> --
> Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
> p...@freebsd.org | TCP/IP since RFC 956
> FreeBSD committer   | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by incompetence.
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> To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
> and follow the instructions there.
>



-- 

*John Phillips*
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Re: [volt-nuts] Making a Reference IC

[Todd Micallef]

Dave,

What is the problem with the original reference? I have not heard of too
many failing. There was also a reply from Hank on another message. Perhaps
he can provide the needed parts from a 732A?

Todd

On Mon, Sep 14, 2015 at 6:45 PM, Dave M <dgmin...@mediacombb.net> wrote:

> After making a mess in my garage while searching for it, it turns out that
> that my Fluke is a 731B.  It appears to use the same Voltage Reference IC
> as the 731A, so no big deal there.
> I found a previous discussion about the 731/732 reference ICs.  Seems that
> the ICs are either from Motorola  (MCA1914/MCA1924/MCA1934) or GE (RA3).
> Doubtful that GE continued production of that IC very long, so my guess is
> that these are Motorola parts.  It's all moot, since none of the parts are
> still in production.  I'm afraid to contact Fluke for a quote on the
> IC/Resistor set.  Don't think my heart could stand the shock.
>
> I'd really like to get this unit back in operation, but I don't want to
> break my bank account to do it.  I have a few LM399s on the shelf, so I
> guess that will be my best approach to a repair.
>
> Thanks for the discussion,
> Dave M
>
>
>
>
> M K wrote:
>
>> On 12/09/2015 23:12, Dave M wrote:
>>
>>> I realize that better references are available.
>>>
>>> I was thinking of resurrecting a long-defunct Fluke 731 that I have
>>> in the garage.  The reference IC is bad in it, and (1) I don't want
>>> to throw it away without a meager attempt at repair, and (2) I don't
>>> want to spend a lot of money on it because it's in pretty bad
>>> physical condition.
>>>
>>> I was hoping that someone could lend a touch of advice on those old
>>> references.  I have a few 1N827A reference zeners, and a washtubful
>>> of transistors.  Maybe something could be cobbled together that
>>> would get the 731 back in operation.  Maybe not to original specs,
>>> but close, which is better than nothing.
>>>
>>> Thanks for your reply,
>>> Dave M
>>>
>>>
>>>
>>> Jack Mcmullen via volt-nuts wrote:
>>>
>>>> Just thinking why would you reinvent a transistor/zener reference
>>>> when the industry's voltage reference chips are in the $2.00 or less
>>>> single quanities with performance far exceeding anything previously
>>>> available in discrete components??
>>>>
>>>>
>>>>
>>>>
>>>> -Original Message-
>>>> From: Dave M dgmin...@mediacombb.net
>>>> To: FEBO Volt-Nuts volt-nuts@febo.com
>>>> Sent: Sat, Sep 12, 2015 1:58 pm
>>>> Subject: [volt-nuts] Making a Reference IC
>>>>
>>>>
>>>>
>>>>
>>>> I was looking at the schematics for the Fluke 731 and 732 voltage
>>>> references.  these, and several other brands and models of voltage
>>>> references, use the same or similar reference ICs as their basis. The
>>>> reference ICs are a Zener/NPN transistor pair on a single
>>>> substrate. Please view in a fixed-width font such
>>>> as Courier.
>>>>
>>>>|
>>>>|
>>>>  C |
>>>>|
>>>>  |
>>>>  |
>>>>   |
>>>>   |  B
>>>>  /|
>>>> / |
>>>>  E |
>>>>|
>>>>+---
>>>>|
>>>> /--/
>>>>   /
>>>>  --
>>>>|
>>>>|
>>>>
>>>> Just thinking... would it be possible to make a reference with
>>>> similar characteristics with discrete components (a low tempco
>>>> Zener and a transistor)?  They would likely have to be closely
>>>> coupled thermally and
>>>> maintained at a constant temperature within an oven or by a peltier
>>>> device.
>>>>
>>>> What criteria would apply to the selection of the parts?
>>>>
>>>> Dave M
>>>>
>>>
>>> There has been some of those references available second hand from
>> ebay, mostly pulled, but some may be counterfeit, so look for sellers
>> with pictures showing it as old.
>>
>
>
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Re: [volt-nuts] Making a Reference IC

[gilb...@nickgilbert.org]

FWIW-I recently contacted a seller of 3458A ref boards asking how/where he was 
able to get  them. He claims that he received many as NOS from a closed 
assembly plant-you folks would know better than I if that story holds water. He 
also says that many are purchased when folks upgrade to the 4ppm option.

I would agree that any of the $99USD are likely fake. However, if its a real 
LTZ1000 and decent components, it could be worth the price. Has anyone ever 
bought one at that price and can confirm whether the ref IC is real?
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Re: [volt-nuts] Making a Reference IC

[Dave M]

The original reference has a shorted Zener.  I verified that with a curve 
tracer (that was a couple years ago, but I remember it well.


I saw the post from Hank, and have emailed him about the 732A stuff that he 
has.


I think my easiest and least expensive approach to getting this instrument 
back on the bench is to build a circuit with an LM399A and fix it onto the 
731B reference board.


Cheers,
Dave M



Todd Micallef wrote:

Dave,

What is the problem with the original reference? I have not heard of
too many failing. There was also a reply from Hank on another
message. Perhaps he can provide the needed parts from a 732A?

Todd

On Mon, Sep 14, 2015 at 6:45 PM, Dave M <dgmin...@mediacombb.net>
wrote:


After making a mess in my garage while searching for it, it turns
out that that my Fluke is a 731B.  It appears to use the same
Voltage Reference IC as the 731A, so no big deal there.
I found a previous discussion about the 731/732 reference ICs.
Seems that the ICs are either from Motorola
(MCA1914/MCA1924/MCA1934) or GE (RA3). Doubtful that GE continued
production of that IC very long, so my guess is that these are
Motorola parts.  It's all moot, since none of the parts are still in
production.  I'm afraid to contact Fluke for a quote on the
IC/Resistor set.  Don't think my heart could stand the shock.

I'd really like to get this unit back in operation, but I don't want
to break my bank account to do it.  I have a few LM399s on the
shelf, so I guess that will be my best approach to a repair.

Thanks for the discussion,
Dave M




M K wrote:


On 12/09/2015 23:12, Dave M wrote:


I realize that better references are available.

I was thinking of resurrecting a long-defunct Fluke 731 that I have
in the garage.  The reference IC is bad in it, and (1) I don't want
to throw it away without a meager attempt at repair, and (2) I
don't want to spend a lot of money on it because it's in pretty bad
physical condition.

I was hoping that someone could lend a touch of advice on those old
references.  I have a few 1N827A reference zeners, and a washtubful
of transistors.  Maybe something could be cobbled together that
would get the 731 back in operation.  Maybe not to original specs,
but close, which is better than nothing.

Thanks for your reply,
Dave M



Jack Mcmullen via volt-nuts wrote:


Just thinking why would you reinvent a transistor/zener reference
when the industry's voltage reference chips are in the $2.00 or
less single quanities with performance far exceeding anything
previously available in discrete components??




-Original Message-
From: Dave M dgmin...@mediacombb.net
To: FEBO Volt-Nuts volt-nuts@febo.com
Sent: Sat, Sep 12, 2015 1:58 pm
Subject: [volt-nuts] Making a Reference IC




I was looking at the schematics for the Fluke 731 and 732 voltage
references.  these, and several other brands and models of voltage
references, use the same or similar reference ICs as their basis.
The reference ICs are a Zener/NPN transistor pair on a single
substrate. Please view in a fixed-width font such
as Courier.

   |
   |
 C |
   |
 |
 |
  |
  |  B
 /|
/ |
 E |
   |
   +---
   |
/--/
  /
 --
   |
   |

Just thinking... would it be possible to make a reference with
similar characteristics with discrete components (a low tempco
Zener and a transistor)?  They would likely have to be closely
coupled thermally and
maintained at a constant temperature within an oven or by a
peltier device.

What criteria would apply to the selection of the parts?

Dave M



There has been some of those references available second hand from

ebay, mostly pulled, but some may be counterfeit, so look for
sellers with pictures showing it as old.




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When the people fear the government, there is tyranny. When the
government fears the people, there is liberty -- Thomas Jefferson


Dave M 



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Re: [volt-nuts] Making a reference IC

[Richard Moore]

I bought my used 3458A ref board on eBay about 5 years ago from a seller in CO. 
It is the genuine article. I can't see how or why anyone would bother to make a 
really good fake board (complete with Vishay metal foil resistors) with a fake 
LTZ 1000A and sell it for $99 If these boards were coming from China, 
maybe...

Sent from my iPad
Snip//
> On Sep 14, 2015, at 4:58 PM, volt-nuts-requ...@febo.com wrote:
> 
>> On 14/09/2015 12:08, Dr. David Kirkby (Kirkby Microwave Ltd) wrote:
>>> On 13 Sep 2015 09:15, "M K"  wrote:
>>> There has been some of those references available second hand from ebay,
>> mostly pulled, but some may be counterfeit, so look for sellers with
>> pictures showing it as old..
>> 
> Nick Gilbert wrote:
> FWIW-I recently contacted a seller of 3458A ref boards asking how/where he 
> was able to get  them. He claims that he received many as NOS from a closed 
> assembly plant-you folks would know better than I if that story holds water. 
> He also says that many are purchased when folks upgrade to the 4ppm option.
> 
> I would agree that any of the $99USD are likely fake.  //snip
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Re: [volt-nuts] Making a Reference IC

[Dave M]

After making a mess in my garage while searching for it, it turns out that 
that my Fluke is a 731B.  It appears to use the same Voltage Reference IC as 
the 731A, so no big deal there.
I found a previous discussion about the 731/732 reference ICs.  Seems that 
the ICs are either from Motorola  (MCA1914/MCA1924/MCA1934) or GE (RA3). 
Doubtful that GE continued production of that IC very long, so my guess is 
that these are Motorola parts.  It's all moot, since none of the parts are 
still in production.  I'm afraid to contact Fluke for a quote on the 
IC/Resistor set.  Don't think my heart could stand the shock.


I'd really like to get this unit back in operation, but I don't want to 
break my bank account to do it.  I have a few LM399s on the shelf, so I 
guess that will be my best approach to a repair.


Thanks for the discussion,
Dave M



M K wrote:

On 12/09/2015 23:12, Dave M wrote:

I realize that better references are available.

I was thinking of resurrecting a long-defunct Fluke 731 that I have
in the garage.  The reference IC is bad in it, and (1) I don't want
to throw it away without a meager attempt at repair, and (2) I don't
want to spend a lot of money on it because it's in pretty bad
physical condition.

I was hoping that someone could lend a touch of advice on those old
references.  I have a few 1N827A reference zeners, and a washtubful
of transistors.  Maybe something could be cobbled together that
would get the 731 back in operation.  Maybe not to original specs,
but close, which is better than nothing.

Thanks for your reply,
Dave M



Jack Mcmullen via volt-nuts wrote:

Just thinking why would you reinvent a transistor/zener reference
when the industry's voltage reference chips are in the $2.00 or less
single quanities with performance far exceeding anything previously
available in discrete components??




-Original Message-
From: Dave M dgmin...@mediacombb.net
To: FEBO Volt-Nuts volt-nuts@febo.com
Sent: Sat, Sep 12, 2015 1:58 pm
Subject: [volt-nuts] Making a Reference IC




I was looking at the schematics for the Fluke 731 and 732 voltage
references.  these, and several other brands and models of voltage
references, use the same or similar reference ICs as their basis. The 
reference ICs are a Zener/NPN transistor pair on a single

substrate. Please view in a fixed-width font such
as Courier.

   |
   |
 C |
   |
 |
 |
  |
  |  B
 /|
/ |
 E |
   |
   +---
   |
/--/
  /
 --
   |
   |

Just thinking... would it be possible to make a reference with
similar characteristics with discrete components (a low tempco
Zener and a transistor)?  They would likely have to be closely
coupled thermally and
maintained at a constant temperature within an oven or by a peltier
device.

What criteria would apply to the selection of the parts?

Dave M



There has been some of those references available second hand from
ebay, mostly pulled, but some may be counterfeit, so look for sellers
with pictures showing it as old.



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Re: [volt-nuts] Making a Reference IC

[M K]

On 14/09/2015 12:08, Dr. David Kirkby (Kirkby Microwave Ltd) wrote:

On 13 Sep 2015 09:15, "M K"  wrote:

There has been some of those references available second hand from ebay,

mostly pulled, but some may be counterfeit, so look for sellers with
pictures showing it as old..

Several sellers have more than 1, but with one photo, so you would have a
hard time arguing that your board is a fake just because it looks newer
than the photo. I believe it is standard practice to photograph a genuine
article but to ship a fake.

In any case, it is probably possible to make a board look older.

A used 3458A fetches several thousand USD, so I find it hard to believe
that many would be broken for parts. But even if there is a reason 3458As
are being broken up, why are other parts not showing up as often as  the
voltage references?

I just looked on ebay for "3458A board" There are 10, of which 6 are the
voltage reference and the other 4 being various other 3458A boards.
Looking for "3458A PCB" changes it to 6 references and 2 two other PCBs. It
seems a bit suspicious to me that the one board that has wider usage than
the others is available in roughly 2~3 times the quantity of all other
boards put together.

We why don't we see 3458A front panels, power supplies etc,  showing up
much - why all the voltage references?

The fact that there seems to be a market for 3458A reference boards
suggests to me that there would be a market for a voltage reference board
based on the same chip, but designed as a stand alone board.

I can think of a few improvements over a 3458A board.

1) Option to run from batteries to keep it as stable as possible when there
are power failures.

It should also make it possible to ship a board to another volt-nut,
keeping it powered in transit.

I don't know the power consumption of the reference,  and I am aware that
there are some issues shipping batteries,  but these seem much more relaxed
if the battery is inside equipment.

2) Option to run chip at a lower temperature than in a 3458A, as some have
claimed is better.

3) Temperature sensor that recorded min and max temperatures during
shipping.

4) Ability to read time board has been powered on.

I for one would buy such a board, if someone produced one, either as a
blank PCB or populated with components & adjusted. Specialist components
would be more readily available is there was a number wanted.

Dave
___

A 731 is not the same beast at all as a 3458, it uses a very different 
reference indeed, I was talking about the IC itself in the 731, not 
buying a completed pcb.

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Re: [volt-nuts] Making a Reference IC

[M K]

On 12/09/2015 23:12, Dave M wrote:

I realize that better references are available.

I was thinking of resurrecting a long-defunct Fluke 731 that I have in 
the garage.  The reference IC is bad in it, and (1) I don't want to 
throw it away without a meager attempt at repair, and (2) I don't want 
to spend a lot of money on it because it's in pretty bad physical 
condition.


I was hoping that someone could lend a touch of advice on those old 
references.  I have a few 1N827A reference zeners, and a washtubful of 
transistors.  Maybe something could be cobbled together that would get 
the 731 back in operation.  Maybe not to original specs, but close, 
which is better than nothing.


Thanks for your reply,
Dave M



Jack Mcmullen via volt-nuts wrote:

Just thinking why would you reinvent a transistor/zener reference
when the industry's voltage reference chips are in the $2.00 or less
single quanities with performance far exceeding anything previously
available in discrete components??




-Original Message-
From: Dave M dgmin...@mediacombb.net
To: FEBO Volt-Nuts volt-nuts@febo.com
Sent: Sat, Sep 12, 2015 1:58 pm
Subject: [volt-nuts] Making a Reference IC




I was looking at the schematics for the Fluke 731 and 732 voltage
references.  these, and several other brands and models of voltage
references, use the same or similar reference ICs as their basis.  The
reference ICs are a Zener/NPN transistor pair on a single substrate.

Please view in a fixed-width font such
as Courier.

   |
   |
 C |
   |
 |
 |
  |
  |  B
 /|
/ |
 E |
   |
   +---
   |
/--/
  /
 --
   |
   |

Just thinking... would it be possible to make a reference with similar
characteristics with discrete components (a low tempco Zener and a
transistor)?  They would likely have to be closely coupled thermally
and
maintained at a constant temperature within an oven or by a peltier
device.

What criteria would apply to the selection of the parts?

Dave M 


There has been some of those references available second hand from ebay, 
mostly pulled, but some may be counterfeit, so look for sellers with 
pictures showing it as old.

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Re: [volt-nuts] Making a Reference IC

[Charles Steinmetz]

Dave wrote:


Just thinking... would it be possible to make a reference with similar
characteristics with discrete components (a low tempco Zener and a
transistor)?  They would likely have to be closely coupled thermally
and maintained at a constant temperature

What criteria would apply to the selection of the parts?


(1) the absolute tempco (mV/C, not ppm/C) of the transistor B-E 
voltage and the Zener voltage need to be very accurately matched over 
the expected temperature range.  (2) the temperature of the 
transistor and Zener substrates must be identical to within very 
small parts of a degree C.  The only practical way to come even close 
with respect to (2) is if both devices are on a monolithic 
substrate.  Even separate dice thermally mounted to a very 
thermally-conductive substrate in one package is a less than optimal 
solution (although that is how the original reference was 
constructed).  Starting with packaged components will just end in tears.


I concur with other advice you have received -- ditch the 1960's 
technology and use one of the excellent low-drift, low-noise voltage 
references that are plentiful these days.  The 731s just have the 
reference IC mounted out in the open, which feeds a 1960s op-amp 
(LM301A in the case of the 731A, LM308A in the case of the 731B) 
mounted out in the open with 1% MF (731A) or precision WW (731B) 
resistors, also mounted out in the open, to produce 10v.  If you do 
nothing but use an LM399 reference and change the op-amp gain 
resistors to suit, using the same type resistors that are in your 
unit now, your 731 will be better than the day it left the factory.


If you replace the op-amp with a modern precision part (I suggest the 
OPA277 -- others may try to talk you into an auto-zero op-amp, but I 
think that would be a mistake in this application), and upgrade the 
gain-setting resistors to ones with better tempcos, it should be very 
much better than the day it left the factory.


None of these changes requires any more design or construction 
expertise than making a new reference IC on the pattern of the 
original, and unlike that effort, they will actually improve the 731 
instead of ruining its performance.


Best regards,

Charles


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[volt-nuts] Making a Reference IC

[Dave M]

I was looking at the schematics for the Fluke 731 and 732 voltage 
references.  these, and several other brands and models of voltage 
references, use the same or similar reference ICs as their basis.  The 
reference ICs are a Zener/NPN transistor pair on a single substrate.

Please view in a fixed-width font such
as Courier.

|
|
  C |
|
 \ |
  \|
   |
   |  B
  /|
 / |
  E |
|
+---
|
 /--/
   /  \
  --
|
|

Just thinking... would it be possible to make a reference with similar 
characteristics with discrete components (a low tempco Zener and a 
transistor)?  They would likely have to be closely coupled thermally and 
maintained at a constant temperature within an oven or by a peltier device.

What criteria would apply to the selection of the parts?

Dave M 
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Re: [volt-nuts] Making a Reference IC

[Jack Mcmullen via volt-nuts]

 Just thinking why would you reinvent a transistor/zener reference when the 
industry's voltage reference chips are in the $2.00 or less single quanities 
with performance far exceeding anything previously available in discrete 
components??




-Original Message-
From: Dave M dgmin...@mediacombb.net
To: FEBO Volt-Nuts volt-nuts@febo.com
Sent: Sat, Sep 12, 2015 1:58 pm
Subject: [volt-nuts] Making a Reference IC

 
 
 
I was looking at the schematics for the Fluke 731 and 732 voltage  
references.  these, and several other brands and models of voltage  
references, use the same or similar reference ICs as their basis.  The  
reference ICs are a Zener/NPN transistor pair on a single substrate. 
 
Please view in a fixed-width font such 
as Courier. 
 
| 
| 
  C | 
| 
  | 
  | 
   | 
   |  B 
  /| 
 / | 
  E | 
| 
+--- 
| 
 /--/ 
   /   
  -- 
| 
| 
 
Just thinking... would it be possible to make a reference with similar  
characteristics with discrete components (a low tempco Zener and a  
transistor)?  They would likely have to be closely coupled thermally and  
maintained at a constant temperature within an oven or by a peltier device. 
 
What criteria would apply to the selection of the parts? 
 
Dave M  
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Re: [volt-nuts] Making a Reference IC

[Dave M]

I realize that better references are available.

I was thinking of resurrecting a long-defunct Fluke 731 that I have in the 
garage.  The reference IC is bad in it, and (1) I don't want to throw it 
away without a meager attempt at repair, and (2) I don't want to spend a lot 
of money on it because it's in pretty bad physical condition.


I was hoping that someone could lend a touch of advice on those old 
references.  I have a few 1N827A reference zeners, and a washtubful of 
transistors.  Maybe something could be cobbled together that would get the 
731 back in operation.  Maybe not to original specs, but close, which is 
better than nothing.


Thanks for your reply,
Dave M



Jack Mcmullen via volt-nuts wrote:

Just thinking why would you reinvent a transistor/zener reference
when the industry's voltage reference chips are in the $2.00 or less
single quanities with performance far exceeding anything previously
available in discrete components??




-Original Message-
From: Dave M dgmin...@mediacombb.net
To: FEBO Volt-Nuts volt-nuts@febo.com
Sent: Sat, Sep 12, 2015 1:58 pm
Subject: [volt-nuts] Making a Reference IC




I was looking at the schematics for the Fluke 731 and 732 voltage
references.  these, and several other brands and models of voltage
references, use the same or similar reference ICs as their basis.  The
reference ICs are a Zener/NPN transistor pair on a single substrate.

Please view in a fixed-width font such
as Courier.

   |
   |
 C |
   |
 |
 |
  |
  |  B
 /|
/ |
 E |
   |
   +---
   |
/--/
  /
 --
   |
   |

Just thinking... would it be possible to make a reference with similar
characteristics with discrete components (a low tempco Zener and a
transistor)?  They would likely have to be closely coupled thermally
and
maintained at a constant temperature within an oven or by a peltier
device.

What criteria would apply to the selection of the parts?

Dave M 



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Re: [volt-nuts] Making a Reference IC

[John Phillips]

they would not be as well matched as if they were on the same chip

On Sat, Sep 12, 2015 at 3:12 PM, Dave M <dgmin...@mediacombb.net> wrote:

> I realize that better references are available.
>
> I was thinking of resurrecting a long-defunct Fluke 731 that I have in the
> garage.  The reference IC is bad in it, and (1) I don't want to throw it
> away without a meager attempt at repair, and (2) I don't want to spend a
> lot of money on it because it's in pretty bad physical condition.
>
> I was hoping that someone could lend a touch of advice on those old
> references.  I have a few 1N827A reference zeners, and a washtubful of
> transistors.  Maybe something could be cobbled together that would get the
> 731 back in operation.  Maybe not to original specs, but close, which is
> better than nothing.
>
> Thanks for your reply,
> Dave M
>
>
>
>
> Jack Mcmullen via volt-nuts wrote:
>
>> Just thinking why would you reinvent a transistor/zener reference
>> when the industry's voltage reference chips are in the $2.00 or less
>> single quanities with performance far exceeding anything previously
>> available in discrete components??
>>
>>
>>
>>
>> -Original Message-
>> From: Dave M dgmin...@mediacombb.net
>> To: FEBO Volt-Nuts volt-nuts@febo.com
>> Sent: Sat, Sep 12, 2015 1:58 pm
>> Subject: [volt-nuts] Making a Reference IC
>>
>>
>>
>>
>> I was looking at the schematics for the Fluke 731 and 732 voltage
>> references.  these, and several other brands and models of voltage
>> references, use the same or similar reference ICs as their basis.  The
>> reference ICs are a Zener/NPN transistor pair on a single substrate.
>>
>> Please view in a fixed-width font such
>> as Courier.
>>
>>|
>>|
>>  C |
>>|
>>  |
>>  |
>>   |
>>   |  B
>>  /|
>> / |
>>  E |
>>|
>>+---
>>|
>> /--/
>>   /
>>  --
>>|
>>|
>>
>> Just thinking... would it be possible to make a reference with similar
>> characteristics with discrete components (a low tempco Zener and a
>> transistor)?  They would likely have to be closely coupled thermally
>> and
>> maintained at a constant temperature within an oven or by a peltier
>> device.
>>
>> What criteria would apply to the selection of the parts?
>>
>> Dave M
>>
>
>
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> volt-nuts mailing list -- volt-nuts@febo.com
> To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
> and follow the instructions there.
>



-- 

*John Phillips*
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