Date   

Re: RM503 ongoing repair saga T620 UNWOUND.

Chuck Harris <cfharris@...>
 

Yes, for a flyback stage, saturation is everything. You
are driving the stage with a unipolar driver, and to get
the best most efficient use of materials, you have to stay
just to the south of saturation or you will fuse everything
into a pile of smoldering rubble.

These, however, are modified Hartley oscillators, and are
intended to stay linear. I think they might have faired
much better if they had been of a flyback design... only
then they would have been more of an EMI nightmare.

-Chuck Harris

David Wise david_wise@... [TekScopes] wrote:

Thanks, I see. I'll keep it in mind when I rewind my 453. In my HP case
(flyback-mode PS), saturation was the limiting factor. It forced me to switch
from discontinuous mode to continuous mode and use a bigger core.

Dave


Re: Multimeter Calibration and Voltage Referance

stefan_trethan
 

I think I did okay, considering that I don't have the volt nuts ;-)

Thanks for the clarification.

ST

On Fri, Mar 27, 2015 at 6:46 PM, Sergey Kubushyn ksi@...
[TekScopes] <TekScopes@...> wrote:
On Fri, 27 Mar 2015, Stefan Trethan stefan_trethan@... [TekScopes] wrote:

Chemical Voltage Standards are er.., Standards. They do NOT require
calibration against same standards because they are based on fundamental
constants so they are primary standards on their own right. They last for at
least tens of years and they were what NIST used as primary standards in not
so distant past until better standards were developed. Unfortunately those
are too big and bothersome to keep in one's garage but good old Weston cells
are more than adequate to calibrate ANY regular instrument including
top-of-the-cream HP 3458A and Datron/Wavetek 1281.

The devil is, as usual in the details. First of all you need SATURATED
Weston cells. _ALL_ those you see on Ebay and wherever else are UNSATURATED
ones so they have their EMF falling with a time so they need periodic checks
against real standards to find their actual EMF. This is the price you pay
for transportability and lower thermal coefficient. These days there is
absolutely no sense for those -- LTZ1000A beats them heads down and way more
convenient. However LTZ1000A voltage source require calibration against
known standard. It is pretty stable when calibrated (after several years of
aging of course) so it holds its voltage very good but ABSOLUTE value is
unknown until calibrated. Even LM399AH is better than old unsaturated Weston
cell and those are available from e.g. DigiKey at less than $10 in single
quantities (LM399AH-ND part number.)

SATURATE Weston cells are standards theirselves. They do NOT need
calibration. Their EMF is based on fundamental constants so they ALWAYS give
the exact (to some degree) ABSOLUTE known voltage that can be used as a
standard to calibrate all other sources against.

However it comes with a cost. First of all they have high temperature
coefficient so you have to keep them in an oil bath with very stable and
precise temperature. Temperature should be either kept at exact spot (that
does not require a very linear and precise thermal sensor but the entire
bath must be calibrated to that spot temperature) or its temperature must be
known with high accuracy if it is not at that spot so necessary correction
can be calculated (that is totally different task from keeping it at exact
spot.)

Then, saturated cells are NOT transportable. They can not be shipped so
there is only one way to get those -- make them in place. It is not terribly
complex or outrageously expensive job but it requires some equipment, tools,
materials, and skills that are usually not available. But if one can do some
relatively basic glassblowing, has adequate chemical lab and chemistry
knowledge it is not a very big deal. All materials can be purchased online,
most of them even not requiring additional purification.

I don't think a chemical voltage standard would be all that useful,
since the voltage does change as they age.
In a cal lab they would be periodically compared wih a superior
standard, and they'd keep track of that change.
So if you got an old dusty standard cell somewhere that change may not be known.
Also temperature and stuff has a big influence.

I think there are some reasonably accurate semiconductor references
for sale on Ebay and elsewhere, in the $40 range.
Those may well be your best option for checking or calibrating low end
multimeters.

ST



On Fri, Mar 27, 2015 at 12:01 PM, Gary Robert Bosworth
grbosworth@... [TekScopes] <TekScopes@...> wrote:
Henryk:

I have seen certified voltage standards at some of the companies where I
worked. They usually had their voltage stamped on the outside to 5-digit
accuracy and traceable to the National Bureau of Standards. Perhaps you
could find one of these cells on eBay.

Gary
On Mar 27, 2015 3:13 AM, "henasau@... [TekScopes]" <
TekScopes@...> wrote:

------------------------------------
Posted by: Stefan Trethan <stefan_trethan@...>
------------------------------------


------------------------------------

Yahoo Groups Links


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* Las Vegas NV, USA < > Miracles require 24-hour notice. *
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------------------------------------
Posted by: Sergey Kubushyn <ksi@...>
------------------------------------


------------------------------------

Yahoo Groups Links



Re: RM503 ongoing repair saga T620 UNWOUND.

Chuck Harris <cfharris@...>
 

Hi John,

I am (or I would be hypocritical) not arguing that you shouldn't do
the tests you have done. I too did them in the process of working
through the reasons for the 547 transformer failures. Initially
I couldn't believe that the epoxy was changing, but rather believed
that the ferrite was changing. I already knew of documented cases
where some of the older powdered iron cores had changed. I also
knew of cases where short circuits caused high flux densities and
permanently changed ferrite cores... invisibly, and not for the
better!

In the process of testing, I found that all of the cores in my
possession, regardless of their origin (eg. old 545's, 547's, etc.),
were nominally the same. I also found that a new copy of the
original winding restored normal operation... that put an end to
my testing of the core material.

If you want to know more about the core, one of the guys bought a
catalog from Cornell-Dublier, the manufacturer of the ferrite, and
it has much of that information in it. I'll have to think where he
put it.

My entire reason for getting into the 547 project was I wanted to
know more about winding HV transformers. I had a project in mind
for a transformer that produced 50KV at about 50ma.

Education is why I do any of this stuff. Thanks to age discrimination,
H1B visa's, and the wholesale exportation of US manufacturing jobs,
it sure isn't for money any more...

-Chuck Harris

'John Snyder' Kochcal@... [TekScopes] wrote:

Well the reason I set up and did the tests were for a couple of reasons.

1. It's another way to measure L with not much more then a scope and pulse
generator, and it covers a higher current mode then other methods. And it's
not clear to me yet where and when the loss are come in to play for at the
operating point. ( sort of like capacitors changing value with the DC
voltage applied)

2. I have not gotten there yet but I was interested in seeing if an arc over
can be "seen" in this test. ( I think one transformer I have does not yet
have a constant short but arcs over only at a higher voltage)

3. I think the properties of the core can be found, and I would like to look
for other cores of a similar nature to do some practice winding/testing on.

4. My interest is 25% to wind a new transformer and 75% to understand
inductors better.

So in terms of just winding a transformer I think I am doing a bunch of
stuff that is not directly necessary but is more educational for me.

John


Re: RM503 ongoing repair saga T620 UNWOUND.

Dave Wise
 

Thanks, I see. I'll keep it in mind when I rewind my 453. In my HP case (flyback-mode PS), saturation was the limiting factor. It forced me to switch from discontinuous mode to continuous mode and use a bigger core.

Dave

________________________________________
From: TekScopes@... [TekScopes@...]
Sent: Friday, March 27, 2015 10:45 AM
To: TekScopes@...
Subject: Re: [TekScopes] RM503 ongoing repair saga T620 UNWOUND.

Hi Dave,

It was imprecise of me to say that saturation testing is "pretty
meaningless in a gapped core." More precise would be to say that
it is meaningless for this exercise.

You cannot push the flux high enough to push this gapped core into
saturation without ruining the primary winding.

-Chuck Harris

David Wise david_wise@... [TekScopes] wrote:
Chuck wrote:

Saturation testing is pretty meaningless in a gapped core. It will be very hard
to saturate, and will not saturate under any condition that the primary will
withstand.
Thank you for your knowledge and information, Chuck, but I respectfully disagree
on this point. Although most of the energy is concentrated in the gap, if you
push the flux high enough, the core will still saturate, and beyond that point
your coil approximates an air-core coil. When I was making a replacement HV
transformer for my HP 740B, I tested a gapped TV flyback core with a switched
voltage source. There was a breakpoint where the current ramp went near vertical
because of the loss of permeability at saturation. I blew up a few transistors
exploring this. :)

Dave Wise

------------------------------------
Posted by: Chuck Harris <cfharris@...>
------------------------------------


------------------------------------

Yahoo Groups Links


Re: Multimeter Calibration and Voltage Referance

Sergey Kubushyn
 

On Fri, 27 Mar 2015, 'J. L. Trantham' jltran@... [TekScopes] wrote:

It's curiosity like this that leads to 'addiction' to metrology. Be
careful.
Yep, it is EXTREMELY contagious and very severe, no cure known :)

---
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* Las Vegas NV, USA < > Miracles require 24-hour notice. *
******************************************************************


Re: Multimeter Calibration and Voltage Referance

Sergey Kubushyn
 

On Fri, 27 Mar 2015, Stefan Trethan stefan_trethan@... [TekScopes] wrote:

Chemical Voltage Standards are er.., Standards. They do NOT require
calibration against same standards because they are based on fundamental
constants so they are primary standards on their own right. They last for at
least tens of years and they were what NIST used as primary standards in not
so distant past until better standards were developed. Unfortunately those
are too big and bothersome to keep in one's garage but good old Weston cells
are more than adequate to calibrate ANY regular instrument including
top-of-the-cream HP 3458A and Datron/Wavetek 1281.

The devil is, as usual in the details. First of all you need SATURATED
Weston cells. _ALL_ those you see on Ebay and wherever else are UNSATURATED
ones so they have their EMF falling with a time so they need periodic checks
against real standards to find their actual EMF. This is the price you pay
for transportability and lower thermal coefficient. These days there is
absolutely no sense for those -- LTZ1000A beats them heads down and way more
convenient. However LTZ1000A voltage source require calibration against
known standard. It is pretty stable when calibrated (after several years of
aging of course) so it holds its voltage very good but ABSOLUTE value is
unknown until calibrated. Even LM399AH is better than old unsaturated Weston
cell and those are available from e.g. DigiKey at less than $10 in single
quantities (LM399AH-ND part number.)

SATURATE Weston cells are standards theirselves. They do NOT need
calibration. Their EMF is based on fundamental constants so they ALWAYS give
the exact (to some degree) ABSOLUTE known voltage that can be used as a
standard to calibrate all other sources against.

However it comes with a cost. First of all they have high temperature
coefficient so you have to keep them in an oil bath with very stable and
precise temperature. Temperature should be either kept at exact spot (that
does not require a very linear and precise thermal sensor but the entire
bath must be calibrated to that spot temperature) or its temperature must be
known with high accuracy if it is not at that spot so necessary correction
can be calculated (that is totally different task from keeping it at exact
spot.)

Then, saturated cells are NOT transportable. They can not be shipped so
there is only one way to get those -- make them in place. It is not terribly
complex or outrageously expensive job but it requires some equipment, tools,
materials, and skills that are usually not available. But if one can do some
relatively basic glassblowing, has adequate chemical lab and chemistry
knowledge it is not a very big deal. All materials can be purchased online,
most of them even not requiring additional purification.

I don't think a chemical voltage standard would be all that useful,
since the voltage does change as they age.
In a cal lab they would be periodically compared wih a superior
standard, and they'd keep track of that change.
So if you got an old dusty standard cell somewhere that change may not be known.
Also temperature and stuff has a big influence.

I think there are some reasonably accurate semiconductor references
for sale on Ebay and elsewhere, in the $40 range.
Those may well be your best option for checking or calibrating low end
multimeters.

ST



On Fri, Mar 27, 2015 at 12:01 PM, Gary Robert Bosworth
grbosworth@... [TekScopes] <TekScopes@...> wrote:
Henryk:

I have seen certified voltage standards at some of the companies where I
worked. They usually had their voltage stamped on the outside to 5-digit
accuracy and traceable to the National Bureau of Standards. Perhaps you
could find one of these cells on eBay.

Gary
On Mar 27, 2015 3:13 AM, "henasau@... [TekScopes]" <
TekScopes@...> wrote:

------------------------------------
Posted by: Stefan Trethan <stefan_trethan@...>
------------------------------------


------------------------------------

Yahoo Groups Links


---
******************************************************************
* KSI@home KOI8 Net < > The impossible we do immediately. *
* Las Vegas NV, USA < > Miracles require 24-hour notice. *
******************************************************************


Re: RM503 ongoing repair saga T620 UNWOUND.

Chuck Harris <cfharris@...>
 

Hi Dave,

It was imprecise of me to say that saturation testing is "pretty
meaningless in a gapped core." More precise would be to say that
it is meaningless for this exercise.

You cannot push the flux high enough to push this gapped core into
saturation without ruining the primary winding.

-Chuck Harris

David Wise david_wise@... [TekScopes] wrote:

Chuck wrote:

Saturation testing is pretty meaningless in a gapped core. It will be very hard
to saturate, and will not saturate under any condition that the primary will
withstand.
Thank you for your knowledge and information, Chuck, but I respectfully disagree
on this point. Although most of the energy is concentrated in the gap, if you
push the flux high enough, the core will still saturate, and beyond that point
your coil approximates an air-core coil. When I was making a replacement HV
transformer for my HP 740B, I tested a gapped TV flyback core with a switched
voltage source. There was a breakpoint where the current ramp went near vertical
because of the loss of permeability at saturation. I blew up a few transistors
exploring this. :)

Dave Wise


Re: Multimeter Calibration and Voltage Referance

Bob Albert
 

I have a gold standard voltmeter, HP 3456A that takes care of everything. I actually have three very accurate voltmeters but the HP is the one on my bench that I use for a master reference.  It's good to better than .01% for most voltages and resistance.  It also measures AC volts.  For current I simply use a measured low value wire wound resistor and calculate the current.  For passive components I use the GR 1658 which is good to maybe 0.1% or better.  For frequency I have a nice counter with OCXO that I occasionally check with WWV.
These instruments are available used (and uncalibrated) for very reasonable prices.  Even uncalibrated they are far better than the everyday type of VOM, including the inexpensive digital ones.
Bob

On Friday, March 27, 2015 10:27 AM, "'Bene's Mails' bene.dienst@... [TekScopes]" <TekScopes@...> wrote:


  To calibrate my whole equipment, I only drive to work!

regards
Ben

From: mailto:TekScopes@...
Sent: Friday, March 27, 2015 6:10 PM
To: TekScopes@...
Subject: Re: [TekScopes] Multimeter Calibration and Voltage Referance

For voltage reference, I use a module I bought on eBay for $20 US. Just search eBay for "voltage reference ad584" (without the quotes) and you will get many examples. Some use the AD584L chip which is laser trimmed to +/- 5 mVolts which is good enough for most of us. Mine came with a hand written "final value" paper that gave the values to 5 digits.
If you want a step up, check out Low Cost Precision Voltage References . This seller offers several great references from simple DC voltage up to voltage (AC and DC), resistance, current, and frequency for $80 US.

| |
| | | | | | | |
| Low Cost Precision Voltage ReferencesCheck out http://voltagestandard.com! voltagestandard.com low cost precision DC voltage references |
| |
| View on www.voltagestandard... | Preview by Yahoo |
| |
| |

From: "henasau@... [TekScopes]" <TekScopes@...>
To: TekScopes@...
Sent: Friday, March 27, 2015 5:12 AM
Subject: [TekScopes] Multimeter Calibration and Voltage Referance

It would be interesting to know how members go about and keep in check accuracy of their workshop multimeters. I have 5 multimeters and each is giving slightly different results. It would be nice to calibrate them to a known voltage standard.

Of course I could pay the money and have them calibrated with the certificate but I am just wondering if there is an easy home made method to address this.

Henryk



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Re: RM503 ongoing repair saga T620 UNWOUND.

ykochcal
 

Well the reason I set up and did the tests were for a couple of reasons.

1. It's another way to measure L with not much more then a scope and pulse
generator, and it covers a higher current mode then other methods. And it's
not clear to me yet where and when the loss are come in to play for at the
operating point. ( sort of like capacitors changing value with the DC
voltage applied)

2. I have not gotten there yet but I was interested in seeing if an arc over
can be "seen" in this test. ( I think one transformer I have does not yet
have a constant short but arcs over only at a higher voltage)

3. I think the properties of the core can be found, and I would like to look
for other cores of a similar nature to do some practice winding/testing on.

4. My interest is 25% to wind a new transformer and 75% to understand
inductors better.

So in terms of just winding a transformer I think I am doing a bunch of
stuff that is not directly necessary but is more educational for me.

John


Re: Multimeter Calibration and Voltage Referance

Benedikt Dienst
 

To calibrate my whole equipment, I only drive to work!

regards
Ben

From: mailto:TekScopes@...
Sent: Friday, March 27, 2015 6:10 PM
To: TekScopes@...
Subject: Re: [TekScopes] Multimeter Calibration and Voltage Referance


For voltage reference, I use a module I bought on eBay for $20 US. Just search eBay for "voltage reference ad584" (without the quotes) and you will get many examples. Some use the AD584L chip which is laser trimmed to +/- 5 mVolts which is good enough for most of us. Mine came with a hand written "final value" paper that gave the values to 5 digits.
If you want a step up, check out Low Cost Precision Voltage References . This seller offers several great references from simple DC voltage up to voltage (AC and DC), resistance, current, and frequency for $80 US.

| |
| | | | | | | |
| Low Cost Precision Voltage ReferencesCheck out http://voltagestandard.com! voltagestandard.com low cost precision DC voltage references |
| |
| View on www.voltagestandard... | Preview by Yahoo |
| |
| |

From: "henasau@... [TekScopes]" <TekScopes@...>
To: TekScopes@...
Sent: Friday, March 27, 2015 5:12 AM
Subject: [TekScopes] Multimeter Calibration and Voltage Referance

It would be interesting to know how members go about and keep in check accuracy of their workshop multimeters. I have 5 multimeters and each is giving slightly different results. It would be nice to calibrate them to a known voltage standard.


Of course I could pay the money and have them calibrated with the certificate but I am just wondering if there is an easy home made method to address this.

Henryk




[Non-text portions of this message have been removed]

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[Non-text portions of this message have been removed]





[Non-text portions of this message have been removed]


Re: Multimeter Calibration and Voltage Referance

 

For voltage reference, I use a module I bought on eBay for $20 US.  Just search eBay for "voltage reference ad584" (without the quotes) and you will get many examples.  Some use the AD584L chip which is laser trimmed to +/- 5 mVolts which is good enough for most of us.  Mine came with a hand written "final value" paper that gave the values to 5 digits.
If you want a step up, check out Low Cost Precision Voltage References .  This seller offers several great references from simple DC voltage up to voltage (AC and DC), resistance, current, and frequency for $80 US.
 
|   |
|   | |   |   |   |   |   |
| Low Cost Precision Voltage ReferencesCheck out http://voltagestandard.com! voltagestandard.com low cost precision DC voltage references |
| |
| View on www.voltagestandard... | Preview by Yahoo |
| |
|   |

  From: "henasau@... [TekScopes]" <TekScopes@...>
To: TekScopes@...
Sent: Friday, March 27, 2015 5:12 AM
Subject: [TekScopes] Multimeter Calibration and Voltage Referance

  It would be interesting to know how members go about and keep in check accuracy of their workshop multimeters. I have 5 multimeters and each is giving slightly different results. It would be nice to calibrate them to a known voltage standard.


Of course I could pay the money and have them calibrated with the certificate but I am just wondering if there is an easy home made method to address this.



Henryk





[Non-text portions of this message have been removed]

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Re: RM503 ongoing repair saga T620 UNWOUND.

Dave Wise
 

Chuck wrote:

Saturation testing is pretty meaningless in a gapped core. It
will be very hard to saturate, and will not saturate under any
condition that the primary will withstand.
Thank you for your knowledge and information, Chuck, but I respectfully disagree on this point. Although most of the energy is concentrated in the gap, if you push the flux high enough, the core will still saturate, and beyond that point your coil approximates an air-core coil. When I was making a replacement HV transformer for my HP 740B, I tested a gapped TV flyback core with a switched voltage source. There was a breakpoint where the current ramp went near vertical because of the loss of permeability at saturation. I blew up a few transistors exploring this. :)

Dave Wise


Re: handheld dvms Mastech MS8264

Kurt Rosenfeld
 

It would be funny if the fixtures from a Tek 575 also worked in the Mastech DMM.

On Fri, Mar 27, 2015 at 12:11 PM, Scott Singelyn scotts@...
[TekScopes] <TekScopes@...> wrote:

Jerry,

Here is a link to the user manual. It explains how hfe measurements are
done.

https://www.techshopbd.com/uploads/product_document/Mastech-MS8264-Digital-Multimeter-Users-Manual.pdf

===============================
Scott Singelyn - N8ZPJ
===============================


------------------------------------

------------------------------------


------------------------------------

Yahoo Groups Links



Re: handheld dvms Mastech MS8264

Scott Singelyn
 

Jerry,

Here is a link to the user manual. It explains how hfe measurements are done.

https://www.techshopbd.com/uploads/product_document/Mastech-MS8264-Digital-Multimeter-Users-Manual.pdf

===============================
Scott Singelyn - N8ZPJ
===============================


handheld dvms Mastech MS8264

 

Hi,

I recently junked my last meter with hfe and temp functions. Looking at Mastech MS8264 on ebay I see a hfe position but no xistor socket. does anyone know how transistors are tested on this machine. what low cost meter is recommended?

Jerry Massengale


Re: Multimeter Calibration and Voltage Referance

Dale H. Cook
 

At 06:12 AM 3/27/2015, Henryk wrote:

It would be interesting to know how members go about and keep in check accuracy of their workshop multimeters.
I own a vintage Hewlett-Packard VTVM calibration system (DC and 400 HZ), originally used by HP field techs. The last calibration run showed the output accuracy as 0.1% or better on all ranges.

Dale H. Cook, Roanoke/Lynchburg, VA
Osborne 1 / Kaypro 4-84 / Kaypro 1 / Amstrad PPC-640
http://plymouthcolony.net/starcity/radios/index.html


Re: Multimeter Calibration and Voltage Referance

n4buq
 

It all goes back to that old saying regarding a man with more than one watch never really knows what time it is...

I do the same as far as using a DMM. No, it isn't calibrated, but my DMMs pretty much agree with each other (and my voltage reference board) and I "trust" them for accuracy over their analog cousins.

For hobby use, that's good enough for me for most work.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "'J. L. Trantham' jltran@... [TekScopes]" <TekScopes@...>
To: TekScopes@...
Sent: Friday, March 27, 2015 8:13:37 AM
Subject: RE: [Bulk] [TekScopes] Multimeter Calibration and Voltage Referance

It's curiosity like this that leads to 'addiction' to metrology. Be
careful.



Since you will never actually know the exact value of any 'standard', you
have to have something in your lab that you would 'trust'. For me, it's a
high quality DMM. Once that is professionally calibrated, you can use it to
'measure' your 'standards' for future reference and act as a 'transfer
standard' to calibrate your other meters.



The 'standards' can be a collection of various devices (resistors, voltage
standards, inductors, capacitors, frequency standards, etc.) or a
'multi-function' calibrator. I like the Fluke 5100B series that can be had
relatively cheaply from time to time but may well need some repair to get
them up and running. It provides DC and AC voltage, resistance and current.




It also depends on what 'standards' you need in order to properly calibrate
your meters.



It's my thought to have such a 'metrology section' in my lab but I have a
long way to go.



Good luck.



Joe



From: TekScopes@... [mailto:TekScopes@...]
Sent: Friday, March 27, 2015 5:13 AM
To: TekScopes@...
Subject: [Bulk] [TekScopes] Multimeter Calibration and Voltage Referance





It would be interesting to know how members go about and keep in check
accuracy of their workshop multimeters. I have 5 multimeters and each is
giving slightly different results. It would be nice to calibrate them to a
known voltage standard.


Of course I could pay the money and have them calibrated with the
certificate but I am just wondering if there is an easy home made method to
address this.



Henryk














Re: Multimeter Calibration and Voltage Referance

J. L. Trantham
 

It's curiosity like this that leads to 'addiction' to metrology. Be
careful.



Since you will never actually know the exact value of any 'standard', you
have to have something in your lab that you would 'trust'. For me, it's a
high quality DMM. Once that is professionally calibrated, you can use it to
'measure' your 'standards' for future reference and act as a 'transfer
standard' to calibrate your other meters.



The 'standards' can be a collection of various devices (resistors, voltage
standards, inductors, capacitors, frequency standards, etc.) or a
'multi-function' calibrator. I like the Fluke 5100B series that can be had
relatively cheaply from time to time but may well need some repair to get
them up and running. It provides DC and AC voltage, resistance and current.




It also depends on what 'standards' you need in order to properly calibrate
your meters.



It's my thought to have such a 'metrology section' in my lab but I have a
long way to go.



Good luck.



Joe



From: TekScopes@... [mailto:TekScopes@...]
Sent: Friday, March 27, 2015 5:13 AM
To: TekScopes@...
Subject: [Bulk] [TekScopes] Multimeter Calibration and Voltage Referance





It would be interesting to know how members go about and keep in check
accuracy of their workshop multimeters. I have 5 multimeters and each is
giving slightly different results. It would be nice to calibrate them to a
known voltage standard.


Of course I could pay the money and have them calibrated with the
certificate but I am just wondering if there is an easy home made method to
address this.



Henryk


Re: Multimeter Calibration and Voltage Referance

n4buq
 

I made a very simple board using one of the voltage reference chips. It's plenty accurate enough for an analog meter. A few high-precision resistive dividers are handy for other voltage ranges. Just a few dollars will get you some pretty good accuracy.

They ones on eBay have some calibration values printed on them and may be just a bit closer (same type of scheme, however) but are, as mentioned, in the $40 range.

Regards,
Barry - N4BUQ

----- Original Message -----
From: "Stefan Trethan stefan_trethan@... [TekScopes]" <TekScopes@...>
To: "TekScopes" <TekScopes@...>
Sent: Friday, March 27, 2015 6:49:17 AM
Subject: Re: [TekScopes] Multimeter Calibration and Voltage Referance

I don't think a chemical voltage standard would be all that useful,
since the voltage does change as they age.
In a cal lab they would be periodically compared wih a superior
standard, and they'd keep track of that change.
So if you got an old dusty standard cell somewhere that change may not be
known.
Also temperature and stuff has a big influence.

I think there are some reasonably accurate semiconductor references
for sale on Ebay and elsewhere, in the $40 range.
Those may well be your best option for checking or calibrating low end
multimeters.

ST



On Fri, Mar 27, 2015 at 12:01 PM, Gary Robert Bosworth
grbosworth@... [TekScopes] <TekScopes@...> wrote:
Henryk:

I have seen certified voltage standards at some of the companies where I
worked. They usually had their voltage stamped on the outside to 5-digit
accuracy and traceable to the National Bureau of Standards. Perhaps you
could find one of these cells on eBay.

Gary
On Mar 27, 2015 3:13 AM, "henasau@... [TekScopes]" <
TekScopes@...> wrote:


Re: Multimeter Calibration and Voltage Referance

stefan_trethan
 

I don't think a chemical voltage standard would be all that useful,
since the voltage does change as they age.
In a cal lab they would be periodically compared wih a superior
standard, and they'd keep track of that change.
So if you got an old dusty standard cell somewhere that change may not be known.
Also temperature and stuff has a big influence.

I think there are some reasonably accurate semiconductor references
for sale on Ebay and elsewhere, in the $40 range.
Those may well be your best option for checking or calibrating low end
multimeters.

ST



On Fri, Mar 27, 2015 at 12:01 PM, Gary Robert Bosworth
grbosworth@... [TekScopes] <TekScopes@...> wrote:
Henryk:

I have seen certified voltage standards at some of the companies where I
worked. They usually had their voltage stamped on the outside to 5-digit
accuracy and traceable to the National Bureau of Standards. Perhaps you
could find one of these cells on eBay.

Gary
On Mar 27, 2015 3:13 AM, "henasau@... [TekScopes]" <
TekScopes@...> wrote:

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