Calibration Of Electronic Equipment In The Home Workshop

[Robert Baer]

Tell us, oh master... what does placing a 1,1 meg resistor in
series with a circuit's power source do to the voltage presented to
the circuit?

Shunt resistors are typically less than an ohm. Show me where
ANYONE uses a 1.1 meg resistor os a current shunt.

I think i said nothing about a series resistor.
Take that handheld DVM and note (rare exceptions) that its input
resistance is 10 megs onany of the voltage scales.
Take further note that the most sensitive scale is (almost always)
200mVFS.
So, by the simple application of ohms law, driving the meter for full
scale reading, the current thru the meter is 20nAFS.
Now, if one places a 1.11Meg resistor in parallel with the DVM, then
the equivalent input rtesistance would then be 1.00Megs and that would
mean, by the simple application of ohms law, driving the meter for full
scale reading, the current thru the meter is 200nAFS.
Und so wieder.

Now if you happen to have a *different* meter that has current scales
moer sensitive than 2mAFS, then this "trick" would not be needed.
Or....if you have absolutely no need for 3.5 or4.5 digit readings of
low currents via your handheld DVM, then this is moot.

 

[Robert Baer]

What a joke that was. When is a 1.1M resistor EVER a current shunt?

What part of ohm's law do you not understand?

 

[Too_Many_Tools]

Laugh, laugh, laugh.....

Thanks for proving my argument MiniPrick.

Keep it up and you will be telling the officer how to fine tune your
cavity search.

TMT

 

[Jim Yanik]

Thanks Jim, I feel like I finally heard something I could put some
stock into. Just to set the record straight, would it be legitimate
to "certify" a device to 3% (DUT specs) using a .03% accurate DMM that
has an NIST cert? Really, it's just a matter of personal curiosity
now.

I'd be leery of that method because vertical gain check is generally done
with a dynamic signal(calibrated sq.wave),to eliminate drift of your
reference (ground) position.Like a TEK PG506.(I wish I had one.)

IIRC,you used a DC source "transfer calibrated" with the DMM to check the
vert.gain.So,literally,the DMM was the "standard" used as the reference,and
that would be listed on the cert.,along with the DC supply.
You just have to be careful to recheck the 0v reference trace position to
be sure it didn't drift.

Gain is usually adjusted on one attenuator setting,and the other ranges
checked to see that they are WITHIN the 3% tolerance,as the attenuators
themselves are usually not adjustable for gain,unless it's a differential
amp,like the 7A13.(don't know about scopes other than TEK.)

 

[David L. Jones]

Did I say they would? I said I would tweak it myself and that it would be
good enough. Stay on track, you're here to prove why it won't work.




Is that an apology? Where are your scematics and submissions?



Show one post where I demonstrated that I don't understand that. You can't.

The problem here is that you read something and then, in your twisted little
way, you interpret it as the poster is stupid and then you go off on some
totaly different train of thought. Like Don Quixote you then procede to
fight a battle against an illusion. You then begin to see every response as
though it's calling you a liar, even if they are just trying to put you back
on track. Many of your comments were valid, but they weren't germane to the
discussion at that point, just like the one you just made here.

Read him like book!

You make it sound like the OP was going to cal some critical lab equipment
at home and that lives were at stake. Then you go on to tout calibrating
your home theater by using a DVD/CD. And that's fine for home theater, but
for lab quality work (like you constantly brag about, and compare everything
to) considering the use of a signal from a CD is just F*CKING STUPID!!! 1Hz
accuracy would be atrocious and you know that very well.



Now tell us why not? Exactly what kind of standard is required to adjust
a scope's vertical response to 3% as it's specs state? And why wouldn't a
.03% meter with traceable certs be good enough? I'm not saying it isn't,
since I never even visited a cal lab, much less worked in one. I just want
to hear your expert opinion on what is required.

You need to understand the concept of ACCEPTABLE ERROR, there is no
perfection only "good enough". What is "good enough" is in the eye of the
beholder, not yours.

I don't think it's any use, after all MassiveProng didn't know that
modern scopes still only have a few percent vertical accuracy, so
obviously he's not quite up to speed on all this low precision stuff erhaps that nameless 4 channel 100MHz scope of his has some
astonishing vertical accuracy?

Dave

 

[MassiveProng]

I think i said nothing about a series resistor.

Dipshit. You said "shunt box" Shunts are series devices.

Take that handheld DVM and note (rare exceptions) that its input
resistance is 10 megs onany of the voltage scales.
Whoopie!

Take further note that the most sensitive scale is (almost always)
200mVFS.
Hahahahaha!

So, by the simple application of ohms law, driving the meter for full
scale reading, the current thru the meter is 20nAFS.
Now, if one places a 1.11Meg resistor in parallel with the DVM, then
the equivalent input rtesistance would then be 1.00Megs and that would
mean, by the simple application of ohms law, driving the meter for full
scale reading, the current thru the meter is 200nAFS.
Und so wieder.

Which says NOTHING about using it to measure current through a
circuit element.

Now if you happen to have a *different* meter that has current scales
moer sensitive than 2mAFS, then this "trick" would not be needed.

Trick? You have defined no trick, and you even have the gall to
declare that your setup isn't used in series.

Or....if you have absolutely no need for 3.5 or4.5 digit readings of
low currents via your handheld DVM, then this is moot.

You need to re-examine your claims.

 

[MassiveProng]

What part of ohm's law do you not understand?

It's the part YOU do not understand that is in question here.

What part of "you change the circuit so much that it is no longer
the same circuit" do you not understand?

 

[MassiveProng]

Thanks for proving my argument MiniPrick.

You have proven nothing, you top posting Usenet retard!

Keep it up and you will be telling the officer how to fine tune your
cavity search.

When you see a crime committed you let someone know, asshole.
Until then shut the **** up, you retarded twit.

TMT

Yes, you.

 

[MassiveProng]

I don't think it's any use, after all MassiveProng didn't know that
modern scopes still only have a few percent vertical accuracy,

Said the total retard that then proceeded to tell us all about his 2%
scope.

Ooops.

 

[David L. Jones]

Said the total retard that then proceeded to tell us all about his 2%
scope.

2% ain't too bad in the scope world, didn't you know? - oh that's
right, you didn't know!
LMAO!

We are all still anxiously awaiting your link to a scope that does
better than a percent or two on the vertical...
What's the matter, your frantic Google search failed you?
Come on, there has to be at least one out there surely, try harder...

Dave

 

[TinyProng]

Meet up with me, and I'll show you
how I manage it.

It's considered polite to bathe regularly enough to deter open sores
erupting across your flesh before making such requests.

HTH.

 

[ehsjr]

Isn't that exactly how my DMM does it?

I don't know what your meter does. I assume it's
like any other. If so, it uses a shunt and develops
a voltage across the shunt so it is the same principle
as what I'm taking about, but not the same values.
AFAIK, they don't use a megohm neighborhood shunt
for low current - but then, I don't have any
meters with an nA scale.

Now come on, the 8 decimal places is only assuming that the scale is in an
Amps range. The meter would be in the 500uA full scale range where 50nA is
only 2 decimal places.

Perhaps I did not make the point clearly.
When you are using your DMM and measuring something in
the neighborhood of 8 decimal places, like tens of nA,
your meter, regardless of scale, will be less accurate
than when it is measuring something in the 2 decimal
place neighborhood. The meter itself is more susceptable
to uncertainty the lower you go. AFAIK, the current
shunt even for low current scales has a much lower
resistance than the 2meg or 100 k I mentioned. That
means that the meter has to work with a lower level
than the 110 mv those resistors produce.

Regarding scaling - DMM's have tens of mV in 2 decimal
places. Most DMM's do not have tens of nA in 2 decimal
places. To get an 8th decimal point current reading into
the 2 decimal point range, convert it to mV with a resistor.

To put it in another perspective, consider a Fluke 187.
It will give .01 uA resolution (2 digits after the decimal)
on the 500 ua scale at a claimed accuracy of +/- .25%.
We'll ignore the further 20 count uncertaincy. That's
a +/- 1.25 uA error. That measurement is useless for the
55 nA current measurement you need. The meter could show
500.00 or 500.05 or 501.25 or whatever and you would not
know whether you had 55 nA or not. On that scale, the
meeter cannot be accurate to 2 decimal places. And you
cannot throw away the third digit after the decimal - it
doesn't exist on the meter, the resolution is too poor.

The same meter, on the 3 volt (3000mV) scale is accurate
to within +/- .025% which is +/- 75 uV - again, ignoring
the further 5 count uncertainty. On the 3 volt scale
with the technique I mentioned where you throw away the
third digit after the decimal, the error is meaningless.
That digit happens to be accurate on this meter and scale,
so the error is meaningless, even if you keep it.

Those are fine ways to measuring static current levels, but they will not
work for me. Until the PIC goes to sleep, the current draw is much higher.
So much so that it would never power up thru a 2M resistor.

So I guess you're stuck with a need that the fancy Fluke
mentioned above cannot meet. How _do_ you measure the
55 nA?

What I would do is bypass the resistor with a switch so
the PIC can power up and run, and monitor it while it
is active by whatever technique you choose, so that you
know it is active. When it goes inactive, open the switch
to measure the voltage across the resistor.

If your volt meter has a 1V maximum at full scale and one can live with 10%
error, then I agree. If it has a 100V range, then you need .01% accuracy on
your equipment to make your measurements, right?

Anyone who is not smart enough to turn his meter
range down from the 100V scale to measure mV
is not smart enough to need nA measurements.

Measuring mV with the range set to 100 is stupid.
And 10% error for a DMM is stupid. I know you are
*not* stupid. So what is your point?

Ed

 

[Anthony Fremont]

Perhaps I did not make the point clearly.
When you are using your DMM and measuring something in
the neighborhood of 8 decimal places, like tens of nA,

The meter doesn't change accuracy based upon the scale it's using, it only
changes resolution. It remains .03% accurate. Whether reading Amps,
milliamps, or microamps.

your meter, regardless of scale, will be less accurate
than when it is measuring something in the 2 decimal
place neighborhood. The meter itself is more susceptable

I guess I wasn't clear or we're not understanding each other. The meter
will be in a ranger where 500uA is the full scale reading. 10's of nA is
two decimal places.

to uncertainty the lower you go. AFAIK, the current
shunt even for low current scales has a much lower
resistance than the 2meg or 100 k I mentioned. That
means that the meter has to work with a lower level
than the 110 mv those resistors produce.

Regarding scaling - DMM's have tens of mV in 2 decimal
places. Most DMM's do not have tens of nA in 2 decimal
places. To get an 8th decimal point current reading into
the 2 decimal point range, convert it to mV with a resistor.

To put it in another perspective, consider a Fluke 187.
It will give .01 uA resolution (2 digits after the decimal)
on the 500 ua scale at a claimed accuracy of +/- .25%.
We'll ignore the further 20 count uncertaincy. That's
a +/- 1.25 uA error. That measurement is useless for the
55 nA current measurement you need. The meter could show
500.00 or 500.05 or 501.25 or whatever and you would not
know whether you had 55 nA or not. On that scale, the

Your error calculation is assuming a full scale reading. The error
(neglecting the count uncertainty) at 50nA is only .125nA, it wouldn't even
show on the display.

But at 50nA it would read .03 to .07uA on my meter including the 2d
uncertainty, plenty good enough for me.

meeter cannot be accurate to 2 decimal places. And you
cannot throw away the third digit after the decimal - it
doesn't exist on the meter, the resolution is too poor.

The same meter, on the 3 volt (3000mV) scale is accurate
to within +/- .025% which is +/- 75 uV - again, ignoring
the further 5 count uncertainty. On the 3 volt scale
with the technique I mentioned where you throw away the
third digit after the decimal, the error is meaningless.
That digit happens to be accurate on this meter and scale,
so the error is meaningless, even if you keep it.

Try looking at the Extech I just ordered. .1%+2d 50000 count.

So I guess you're stuck with a need that the fancy Fluke
mentioned above cannot meet. How _do_ you measure the
55 nA?

That's why I didn't buy the Fluke. The meter I bought will give me 10nA
resolution. I know it won't be dead on when reading 50nA, but it will be
close enough that I know that I didn't leave some pull-ups turned on or some
other peripheral pidling away the juice. In current mode the Extech will be
good enough for me to be sure of what's happening. Any worse accuracy, and
I couldn't be sure.

What I would do is bypass the resistor with a switch so
the PIC can power up and run, and monitor it while it
is active by whatever technique you choose, so that you
know it is active. When it goes inactive, open the switch
to measure the voltage across the resistor.

Yes, I have done time-wasting methods like this before, that's why I want a
new meter, DSO and a logic analyzer.

Anyone who is not smart enough to turn his meter
range down from the 100V scale to measure mV
is not smart enough to need nA measurements.

Measuring mV with the range set to 100 is stupid.
And 10% error for a DMM is stupid. I know you are
*not* stupid. So what is your point?

The 10% error is due to your technique not the DMM, you said so yourself,
and I quote:

"> For 11 uA, put a 10K .01% resistor in series with

the supply and measure .11 volts across it. The voltage
would range from 0.109989 to 0.110011. Keep only
2 decimal places. Your computed current, worst case,
would be off by 1 uA

For 50 nA, use a 2 meg 1% resistor and measure .10
volts across it. The voltage would range from .099
to .101 taking the 1% into account. Throw out the
last digit. Your current computation would be off
worst case, by 5 nA."

By my calculations, a 5nA error on a 50nA reading is a 10% error or did I
miss something?

I agree that these techniques are valid and worthwhile at times, but I will
stick with the convenience and accuracy of a $200 meter instead of buying $5
resistors. I've got a tracking number and it should be here tomorrow,
I can't wait. I reall can't wait til my scope gets here. ))))))

 

[David L. Jones]

The meter doesn't change accuracy based upon the scale it's using, it only
changes resolution. It remains .03% accurate. Whether reading Amps,
milliamps, or microamps.


I guess I wasn't clear or we're not understanding each other. The meter
will be in a ranger where 500uA is the full scale reading. 10's of nA is
two decimal places.






Your error calculation is assuming a full scale reading. The error
(neglecting the count uncertainty) at 50nA is only .125nA, it wouldn't even
show on the display.

But at 50nA it would read .03 to .07uA on my meter including the 2d
uncertainty, plenty good enough for me.



Try looking at the Extech I just ordered. .1%+2d 50000 count.





That's why I didn't buy the Fluke. The meter I bought will give me 10nA
resolution. I know it won't be dead on when reading 50nA, but it will be
close enough that I know that I didn't leave some pull-ups turned on or some
other peripheral pidling away the juice. In current mode the Extech will be
good enough for me to be sure of what's happening. Any worse accuracy, and
I couldn't be sure.


Yes, I have done time-wasting methods like this before, that's why I want a
new meter, DSO and a logic analyzer.









The 10% error is due to your technique not the DMM, you said so yourself,
and I quote:

"> For 11 uA, put a 10K .01% resistor in series with


By my calculations, a 5nA error on a 50nA reading is a 10% error or did I
miss something?

I agree that these techniques are valid and worthwhile at times, but I will
stick with the convenience and accuracy of a $200 meter instead of buying $5
resistors. I've got a tracking number and it should be here tomorrow,
I can't wait. I reall can't wait til my scope gets here. ))))))

We expect internal pics to be posted ASAP!

I'm curious about the build quality of the Extech...

Dave

 

[Anthony Fremont]

We expect internal pics to be posted ASAP!

Well, I guess while I'm in there butchering up the knob spring and resetting
the cal using my Micronta, I might as swell snap some pics. ;-)

I'm curious about the build quality of the Extech...

Me too, for that much money it better be as good as a Fluke.

The scope wont be here for a couple of weeks. :-( I hope it's as good as
the manual makes it sound. What do you think of this:
http://cgi.ebay.com/OWON-PORTABAL-D...yZ104247QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

 

[David L. Jones]

Well, I guess while I'm in there butchering up the knob spring and resetting
the cal using my Micronta, I might as swell snap some pics. ;-)

No fair waving the red flag at the bull now, he must be tired from all
that charging!

Me too, for that much money it better be as good as a Fluke.

The scope wont be here for a couple of weeks. :-( I hope it's as good as
the manual makes it sound. What do you think of this:http://cgi.ebay.com/OWON-PORTABAL-DIGITAL-Oscilloscope-EDU5022M-25MHZ...

Love the Jinglish:
"Digital popularization storm-the best substitute of EDU series
digital oscilloscope for analog oscilloscope

EDU digital storage oscilloscope is the best choice to substitute for
traditional analog oscilloscope though it don't coming with surprising
function and specification. Thanks to the creative R&D thoughts and
strict cost control, EDU series is outstanding when compete with
analog oscilloscope even in price.
EDU digital storage oscilloscopes display by STN LCD big screen in
compact design, it is available at bandwidth of 20MHz to 40MHz and
real sample rate of 100Ms/S.The series satisfy the detection of
electric manufacturing production lines as well as basic mathematics
needs.

Hesitation is wasting! We highly expect the "Digital popularization
storm "will bring the reliable measurement instruments which "Meet
your best needs" for you."

Hilarious!

25MHz bandwidth and 100MS/s ain't exactly going to blow the lab down.
It sucks for sure, but the question is only buy how much?

Dave

 

[Anthony Fremont]

The scope wont be here for a couple of weeks. :-( I hope it's as
good as the manual makes it sound. What do you think of this:
http://cgi.ebay.com/OWON-PORTABAL-D...yZ104247QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Oops wrong one, try here:
http://www.saelig.com/miva/merchant.mvc?Screen=PROD&Product_Code=PSSA004&Category_Code=PSSA

60MHz, TFT 6K depth, all the normal bells and whistles (USB memory stick,
printer etc) and I think it might have a 7.8" screen. Not bad for under
$600. It seems to be a match for the current generation of thin (6") depth
units from China. For only $70 more, you get a 3hr battery and charger.

 

[Anthony Fremont]

No fair waving the red flag at the bull now, he must be tired from all
that charging!


Love the Jinglish:
"Digital popularization storm-the best substitute of EDU series
digital oscilloscope for analog oscilloscope

EDU digital storage oscilloscope is the best choice to substitute for
traditional analog oscilloscope though it don't coming with surprising
function and specification. Thanks to the creative R&D thoughts and
strict cost control, EDU series is outstanding when compete with
analog oscilloscope even in price.
EDU digital storage oscilloscopes display by STN LCD big screen in
compact design, it is available at bandwidth of 20MHz to 40MHz and
real sample rate of 100Ms/S.The series satisfy the detection of
electric manufacturing production lines as well as basic mathematics
needs.

Hesitation is wasting! We highly expect the "Digital popularization
storm "will bring the reliable measurement instruments which "Meet
your best needs" for you."

Hilarious!

25MHz bandwidth and 100MS/s ain't exactly going to blow the lab down.
It sucks for sure, but the question is only buy how much?

Check that other one at Saelig, it's made by Owon. 60MHz 250Msa/s 6K
PDS6062T not bad looking.

Yeah that's what I loved about the Rigol manual, not a trace of engrish
anywhere. I wonder if a customer wrote it for them. ;-)

 

[Robert Baer]

Dipshit. You said "shunt box" Shunts are series devices.





Which says NOTHING about using it to measure current through a
circuit element.




Trick? You have defined no trick, and you even have the gall to
declare that your setup isn't used in series.




You need to re-examine your claims.

Use a dictionary, if you have one and look up the word "shunt".
Hint: do not use the quotes.

 

[Robert Baer]

No fair waving the red flag at the bull now, he must be tired from all
that charging!




Love the Jinglish:
"Digital popularization storm-the best substitute of EDU series
digital oscilloscope for analog oscilloscope

EDU digital storage oscilloscope is the best choice to substitute for
traditional analog oscilloscope though it don't coming with surprising
function and specification. Thanks to the creative R&D thoughts and
strict cost control, EDU series is outstanding when compete with
analog oscilloscope even in price.
EDU digital storage oscilloscopes display by STN LCD big screen in
compact design, it is available at bandwidth of 20MHz to 40MHz and
real sample rate of 100Ms/S.The series satisfy the detection of
electric manufacturing production lines as well as basic mathematics
needs.

Hesitation is wasting! We highly expect the "Digital popularization
storm "will bring the reliable measurement instruments which "Meet
your best needs" for you."

Hilarious!

25MHz bandwidth and 100MS/s ain't exactly going to blow the lab down.
It sucks for sure, but the question is only buy how much?

Dave

...."basic mathematics needs" ?????