Calibration Of Electronic Equipment In The Home Workshop

[Anthony Fremont]

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

Man does that ever sound like a personal threat.

 

[MassiveProng]

I believe we were talking about scopes only being about 3% accurate in the
vertical.

I think you should read a fucking thread before you mouth off,
dipshit. You ain't too bright, boy.

QUOTED:

Me:

Your micronta? Bwuahahahahahah!

The ditz:
Since 3% accuracy is considered good in the scope world, I think it
would do
fine.

 

[MassiveProng]

Man does that ever sound like a personal threat.

You're an idiot.

 

[Robert Baer]

You surely didn't mean tens of _mA_, did you? I build stuff with PICs as
you know, and some of it is designed to run on batteries and needs to go for
long periods of time unattended. The current draw for a 12F683 running at
31kHz is 11uA, sleep current is 50nA. If I could only measure current to
"tens of mA", I'd never know if the PIC was setup right for low current draw
and I certainly couldn't have any idea of expected battery life. I wouldn't
even know if it was sleeping until it ate thru some batteries in a few days
instead of six or eight months. I think I have a need to measure fractions
of a uA.




When he needs it he needs it, what can I say? Do I really "need" a new DSO?
Well I've managed to get by all this time without one, so maybe you think I
don't really "need" one. I see it like this though, I don't get allot of
time to tinker anymore. I'd like to spend it more productively. Instead of
fumbling around and trying to devise silly methods to make my existing
equipment do something it wasn't designed to (like going off on a tangent to
build a PIC circuit that will trigger my scope early so I can try to see
some pre-trigger history).




I don't know if I really agree with that. ;-)

Here is a good "trick" to measure low currents with your DVM.
Make a switchable shunt box with (at least) the following full scale
ranges: 200nA (shunt resistor 1.11 megs), 2uA (shunt resistor 101K),
20uA (shunt resistor 10.0K), 200uA (shunt resistor 1.00K).
Put a twisted pair of leads (red, black) with banana plugs (red,
black) running out of the box via a small grommet, to plug into your DVM
set to the 200mV scale; a pair of (red, black) banana jacks with 0.75
"spacing is mounted on the box for your test leads.
Hint: add to the legend the parallel resistance of the system
(200nA/1M, 2uA/100K, etc) as a reminder of the resistance of this
current meter scheme.
Added hint: the 200MV scale is good for 20nA full scale, just
remember the meter resistance is 10 megs.

 

[Clint Sharp]

Sorry, you dumbfuck, but you assuming that all TVs have this
capacity proves even further how little you know about it.

So your TV doesn't have a service mode and it doesn't have any pots to
tweak? How, exactly, does it get adjusted in the factory or by a service
tech then? Just because *you* don't have access to it doesn't mean it
doesn't have a service mode where adjustments can be made via menu.

 

[Anthony Fremont]

I surely meant tens of mA.

I build stuff with PICs as

You may, but not accuracy below the tens of _mA_ digit.
When you need accuracy below tens of mA, you measure
voltage across a resistance. It doesn't make a lot of

Isn't that exactly how my DMM does it?

sense to look for your meter to be accurate to 8 decimal
places for your .00000005 amp reading.

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.

Here's how you do it with accuracy at the tens of _mV_ digit:

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.

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.

With a voltmeter accurate to 2 decimal places.
I don't know why you would

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?

I asked, looking for concrete cases. Your case
with the PIC is an excellent example of when a
person needs to know about really small currents.
It definitely fits into the difference I had in mind
between "needs" and "wants". But it does not mean he
needs accuracy out to 8 decimal places. He needs it to
2 decimal places, as was shown. Three decimal places
would be nice.

Aren't you arbitrarily relocating your base measurement scale to uA or nA
and then claiming that you're only being accurate to two decimal places?
You are still measuring current to the same "8 decimal places" in terms of
whole Amps, you just moved the decimal around.

IMO, it's not about decimal places at all, that's just a matter of scale.
It's about accuracy. 10% ain't good enough, and that's only accounting for
the error in your shunt resistors.

I have no opinion on that, and it would be irrelevant
if I did. I don't know what your situation is.


Well, you're free to argue against having the best
instrumentation you can afford, or having references
to check it against or getting it calibrated or
whatever, if that's how you feel. I tend to err on

Actually, I'm all for that part.

the side of wanting the best even when it is
not the best fit for what I really need.

And this is what I do as well. I'd rather have a margin of overkill than to
be constantly living with sacrifice by saving a couple of bucks on a NRE.
What I wasn't "sure" about was whether _you_ really felt that way. ;-)

 

[Clint Sharp]

Stupid shit. The suggestion I posed mine against was some twit
suggesting WWV and a 1kHz tone, which is about as old hat as it gets.

You should really learn to read ENTIRE threads before you mouth off,
jackass.

And I asked, does the stability of the clock in a Dvd player affect the
accuracy of the tones replayed, you still haven't given a proper answer
to that. Maybe because you know it does and that blows down your house
of cards.

 

[Clint Sharp]

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

For the moment I really think you need to avoid situations where your
'intellect' and experience could be challenged as it seems to provoke an
anger response which must be detrimental to whichever course of therapy
you are in. If you're not in therapy, you should consider it. Life's too
short to be that angry all the time.

 

[Anthony Fremont]

I think you should read a fucking thread before you mouth off,
dipshit. You ain't too bright, boy.

QUOTED:

Me:


The ditz:
Since 3% accuracy is considered good in the scope world, I think it
would do
fine.

That's not the part I had in mind, but that will do for now. You really
didn't understand the statement did you? I'm talking about scope accuracy,
nothing about the meter at this point because I already brought that up IN
MY FIRST POST IN THIS THREAD.

QUOTED:
"Are you suggesting that I should drag it across town, spend $200 and be
without it for 2 weeks just to get it adjusted by some obstinate, E-1 grade
line tech, instead of using a brand new DMM w .03% accuracy to tweak it
myself? I'm quite sure that my Micronta is up to the task to be honest."

What part of that don't you understand? PLEASE READ MY POSTS BEFORE PISSING
YOURSELF!!!!! If you don't understand something just ask for help. A .03%
METER CAN BE USED, ESPECIALLY WHEN THAT METER IS AVAILABLE WITH NIST CERTS,
NOW CAN'T IT????

Now, go off, change your nym again and see how many posts you can make
before I recognize you.

Now, please FOAD unless you can learn to control yourself better.

 

[Robert Baer]

It doesn't matter how many "places" you "spot check" it, you are not
going to get the accuracy of your comparison standard on the device
you intend to set with it. What you do is take the basic INaccuracy
of the device needing to be set, and add to it the basic INaccuracy of
the standard to which you are setting it. You CANNOT get any closer
than that. So, a 0.5% meter, and a 0.5% scope cannot be used together
to make the scope that accurate. You need a *finer* standard than the
accuracy level you wish to achieve.

You need to understand that as a basic fact, chucko.

Furthermore, an analog scope cannot measure better than 1% (ie 0ne
part in 100 of what is on the scope face).
Now one can "cheat" by using a precision offset differenced with an
input and that difference amplified to *display* (part of) that
difference: note the "Z", the "W", and the more modern "7A13" type plugins.
But *on the screen*, i defy anyone to consistently "read" better than
one part in 100 (ie if 10 divisions on screen, read to better than 1
division on a consistent basis.
Thus, for a scope, one might use standards good to 5 or more places,
but the result will be no better than what has been called "slide rule
accuracy".
Do you believe all 15 digits of each and every number in a computer
printout?

 

[Robert Baer]

Modern instrument accuracies are so good, and keep their setup so
well, to open one up and tweak it with less than a professional
calibration standard available is ludicrous in the extreme.

No matter how smart one is, if one has an instrument, and wants to
test accuracy, one should make an appearance somewhere where an
already recently calibrated instrument is available to EXAMINE your
instrument against.

NONE should be "adjusted" at all ever if the variance is too small
to warrant it, and even pro calibrators follow this creed. If at all
possible, their main task is to VERIFY an instrument's accuracy
WITHOUT making ANY adjustment. ANY that DO need adjustments are
typically marked "defective" and require a factory inspection/repair.

I speak from experience, so I don't care what the ToolTard thinks
about his capacity for the task, he is a fucking retard if he tries it
without first checking his gear against known good gear.

It really is THAT SIMPLE.

Check, and check mate; end game.

 

[Clint Sharp]

Man does that ever sound like a personal threat.

I'm not the least worried by him. He's just an interesting diversion,
provoking an anger response from him is a bit like shooting fish in a
barrel but it's starting to get boring as it's so easy and his
vocabulary is pretty small really.

 

[Robert Baer]

Absolutely incorrect!

If you do that, the MINIMUM error is 0.5%. It is ALWAYS greater
than that value by that value plus the error of the device you think
you set.

How can you not understand that basic fact?




Absolutely INCORRECT!

The error of a device is NOT tied to how it got set or what it got
set with, dipshit, it is tied to precision of the circuits the device
are based upon.




Wanna bet?

Further more, if one did this procedure using thousands of meters to
"calibrate" thousands of other meters, the net resulting error is *NOT*
the sum; it is the square root of the sum of the squares!
But taking only *one* reference ("standard") and using it to
"calibrate" only one device, the result is technically indeterminate but
may be bounded by the sum of the (instrument) errors - and could be
*worse* (anybody hear of "cockpit errors"?).

 

[Robert Baer]

I surely meant tens of mA.

I build stuff with PICs as



You may, but not accuracy below the tens of _mA_ digit.
When you need accuracy below tens of mA, you measure
voltage across a resistance. It doesn't make a lot of
sense to look for your meter to be accurate to 8 decimal
places for your .00000005 amp reading.

Here's how you do it with accuracy at the tens of _mV_ digit:

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.

With a voltmeter accurate to 2 decimal places.
I don't know why you would



I asked, looking for concrete cases. Your case
with the PIC is an excellent example of when a
person needs to know about really small currents.
It definitely fits into the difference I had in mind
between "needs" and "wants". But it does not mean he
needs accuracy out to 8 decimal places. He needs it to
2 decimal places, as was shown. Three decimal places
would be nice.



I have no opinion on that, and it would be irrelevant
if I did. I don't know what your situation is.



Well, you're free to argue against having the best
instrumentation you can afford, or having references
to check it against or getting it calibrated or
whatever, if that's how you feel. I tend to err on
the side of wanting the best even when it is
not the best fit for what I really need.

Ed

Please see my earlier post regarding the use of a shunt box for a DVM.

 

[Robert Baer]

On Sat, 03 Mar 2007 19:21:44 -0800, MassiveProng


MassiveProng wrote:

On 2 Mar 2007 15:09:30 -0800, "David L. Jones" <[email protected]>
Gave us:


Which is why you do it for each range and then spot check it to see
that there is no funny business. Perfectly valid technique for home
calibration of a scope vertical scale.

Dave

It doesn't matter how many "places" you "spot check" it, you are not
going to get the accuracy of your comparison standard on the device
you intend to set with it. What you do is take the basic INaccuracy
of the device needing to be set, and add to it the basic INaccuracy of
the standard to which you are setting it. You CANNOT get any closer
than that. So, a 0.5% meter, and a 0.5% scope cannot be used together
to make the scope that accurate. You need a *finer* standard than the
accuracy level you wish to achieve.

You need to understand that as a basic fact, chucko.

The "basic fact" here is that we were talking about adjusting a 3% scope
with a .03% meter.

]
Nope. READ HIS replies. He was talking about using a 3% meter.


Now that the number are back where they belong, please
procede to restate your case.

**** you. Read HIS criteria, dipshit, don't impose yours. Remeber,
it was ME that stated that the cal device had to be ten times more
accurate than the target to be cal'd. So **** off.


The scope's vertical sensitivity could easily
be adjusted to within 3% using said meter, now can't it? Just like Keith
says......

That is NOT what the retarded bastard said, you retarded bastard.

Ahhh, who actually uses a scope to make accurate measurements?

I guess the same idiots that claim they can calibrate one with a 3%
meter.

My point exactly.

Also, if you do NOT know how to make accurate measurements with
scopes, you should be in some other industry.

More to the point, if you dont understand the concept of error then
you should be in another industry.

*POLITICS*! !oops! did not mean to swear!

 

[Robert Baer]

On Sat, 03 Mar 2007 19:21:44 -0800, MassiveProng


MassiveProng wrote:

On 2 Mar 2007 15:09:30 -0800, "David L. Jones" <[email protected]>
Gave us:


Which is why you do it for each range and then spot check it to see
that there is no funny business. Perfectly valid technique for home
calibration of a scope vertical scale.

Dave

It doesn't matter how many "places" you "spot check" it, you are not
going to get the accuracy of your comparison standard on the device
you intend to set with it. What you do is take the basic INaccuracy
of the device needing to be set, and add to it the basic INaccuracy of
the standard to which you are setting it. You CANNOT get any closer
than that. So, a 0.5% meter, and a 0.5% scope cannot be used together
to make the scope that accurate. You need a *finer* standard than the
accuracy level you wish to achieve.

You need to understand that as a basic fact, chucko.

The "basic fact" here is that we were talking about adjusting a 3% scope
with a .03% meter.

]
Nope. READ HIS replies. He was talking about using a 3% meter.


Now that the number are back where they belong, please
procede to restate your case.

**** you. Read HIS criteria, dipshit, don't impose yours. Remeber,
it was ME that stated that the cal device had to be ten times more
accurate than the target to be cal'd. So **** off.


The scope's vertical sensitivity could easily
be adjusted to within 3% using said meter, now can't it? Just like Keith
says......

That is NOT what the retarded bastard said, you retarded bastard.

Ahhh, who actually uses a scope to make accurate measurements?


I guess the same idiots that claim they can calibrate one with a 3%
meter.

My point exactly.

Good thing I never made that claim.

More to the point, if you dont understand the concept of error then
you should be in another industry.

That is about the gist of what I have been trying to tell them.

Some dope thinking he can adjust his meter accurately with a damned
drifty voltage reference chip should have his head examined, not his
instruments!

Shoot, he could hae a precision, very stable voltage reference, and
still bollix up the works!

 

[Anthony Fremont]

Actually,one CAN calibrate an instrument to a greater accuracy than
it's specified accuracy,-for a short time-;it's called a transfer
standard.
Of course,there are limits to how much greater accuracy you can
achieve,based on resolution and repeatability.

For ordinary cals,your standard should be at least 4x better than the
DUT. 10x is great.

Thanks Jim. It's nice to read something that makes me feel like I still
retain some semblance of sanity. That all seems completely reasonable, and
you didn't even have to curse or make threats. ;-)

 

[MassiveProng]

Here is a good "trick" to measure low currents with your DVM.
Make a switchable shunt box with (at least) the following full scale
ranges: 200nA (shunt resistor 1.11 megs), 2uA (shunt resistor 101K),
20uA (shunt resistor 10.0K), 200uA (shunt resistor 1.00K).
Put a twisted pair of leads (red, black) with banana plugs (red,
black) running out of the box via a small grommet, to plug into your DVM
set to the 200mV scale; a pair of (red, black) banana jacks with 0.75
"spacing is mounted on the box for your test leads.
Hint: add to the legend the parallel resistance of the system
(200nA/1M, 2uA/100K, etc) as a reminder of the resistance of this
current meter scheme.
Added hint: the 200MV scale is good for 20nA full scale, just
remember the meter resistance is 10 megs.

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.

 

[MassiveProng]

So your TV doesn't have a service mode and it doesn't have any pots to
tweak? How, exactly, does it get adjusted in the factory or by a service
tech then? Just because *you* don't have access to it doesn't mean it
doesn't have a service mode where adjustments can be made via menu.

More proof that you know very little if anything at all about FPDs.

 

[MassiveProng]

And I asked, does the stability of the clock in a Dvd player affect the
accuracy of the tones replayed, you still haven't given a proper answer
to that. Maybe because you know it does and that blows down your house
of cards.

You're a fucking retard. I could take a hundred different brand and
quality DVD players and that one set-up disc, and all 100 of the
players would produce the EXACT same tone with less than 1Hz error.

Try again, you totally retarded ****!