Hello all
I have a few digital multimeters which are in need of calibrating, cheap
meters.
How do I make a DC calibrating voltage source with say 1% accuracy, any
voltage, prefer close to 1999 reading.
Thank you very much
Bert

Bert lijbertv_at_xsinet_dot_co_dot_za wrote in message
...
Hello all
I have a few digital multimeters which are in need of calibrating, cheap
meters.
How do I make a DC calibrating voltage source with say 1% accuracy, any
voltage, prefer close to 1999 reading.
Thank you very much
Bert



Indirectly via a high precision resistor perhaps.
I have some 8 Kohm ones to 0.01 per cent accuracy
at manufacture anyway, presumably other sources of
such resisrors

one of my tips from URL below

Callibrating a DVM and cross-calibrating a standard cell
For anyone with access to a Weston cell but not access to a 5 or 6 digit
DVM.
I think this is how I cross-calibrated.
I've dug out the docs and mine was calibrated at manufacture as
1.01866V at 20 deg C and -40 ppm/ deg C , 14 March 1979.
estimate of uncertainty 10 ppm
Perhaps 5 years ago I did the following with my cell and someone else's
secondary standard cell.
My DVM has a 300mV range for its 4 digits, or 200mV will do the same.
With a NiCad in good condition in mid discharge and left for some hours to
reach room temperature is a nominal 1.2V.
What the actual voltage is does not matter as long as it is stable.
Assume for convenience here 1.2V.
Only use with DVMs ( high input impedence) .
Then commoning negatives of Weston cell and NiCad, measured the difference
so came in the 200mV range.
Which brings it into the first 6 of 1.01866 then ratioing of the flashing
digits gives an estimate for the fifth digit.
So reading of 181.4 mV
With DVM 2/3 time reading 181.4 and 1/3 time reading 181.3 so implying
Weston Cell voltage of 1.01863 at 22 degrees C. The other cell / DVM test
was about 1/3 to 2/3 the other way round on last digit agreeing with that
cell's yearly calibration value.
At the same time I checked a small standard cell salvaged from a bit of kit
and it too was many years old but almost the same voltage, only last digit
different again.


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

I misread you were after 0.1 percent accuracy, dirty monitor.
For 1 percent a 0.1 percent band gap reference would be fine
You really have to go one order of precision better
than what you are after.

Hello N Cook
You brought me at an idea.
Somewhere on the back of my shelf I have a very good mV meter, with the
papers for working out the amount of mV at a certain temperature on all
thermocouples, with a cold junction in between, normally in melting ice.
Can not remember the make, but very expensive.
This meter has a standard cell for reference, it also has a mV source coming
out.
Hope the standard cell is still working after 20 years and two new C cells
in it.
Thank you very much for the explaining.
My head is becoming a bit rusted through age.
Bert.

"Bert" lijbertv_at_xsinet_dot_co_dot_za wrote in
:

Hello all
I have a few digital multimeters which are in need of calibrating, cheap
meters.
How do I make a DC calibrating voltage source with say 1% accuracy, any
voltage, prefer close to 1999 reading.
Thank you very much
Bert



bandgap reference diodes.
They come in several voltages,much more accurate than the typical 3.5digit
DMM.
You can string several in series to obtain the voltages you want.

OR,you could buy an old Fluke differential voltmeter;they are precision
voltage sources.

--
Jim Yanik
jyanik
at
kua.net

"Bert" lijbertv_at_xsinet_dot_co_dot_za wrote in message
...
Hello all
I have a few digital multimeters which are in need of calibrating, cheap
meters.
How do I make a DC calibrating voltage source with say 1% accuracy, any
voltage, prefer close to 1999 reading.

If they are cheap, are you sure they can easily be calibrated?

Can you borrow a calibrated meter?

A fresh silver oxide cell is going to be very close to 1.55 volts and can be
used as an initial check.

"Bert" lijbertv_at_xsinet_dot_co_dot_za wrote in message
...
Hello all
I have a few digital multimeters which are in need of calibrating, cheap
meters.
How do I make a DC calibrating voltage source with say 1% accuracy, any
voltage, prefer close to 1999 reading.

If they are cheap, are you sure they can easily be calibrated?

Can you borrow a calibrated meter?

A fresh silver oxide cell is going to be very close to 1.55 volts and can be
used as an initial check.


Both can be calibrated and have presets inside, they are close with the help
of some new batteries but not good enough.
I do not know anyone with a callibrated meter.
Thanks both of you.

In article ,
Charles Schuler wrote:
A fresh silver oxide cell is going to be very close to 1.55 volts and
can be used as an initial check.

Is that the most readily available cell for this purpose? Years ago I was
told it was a zinc carbon - but *then* there might not have been many
alternatives.

--
*You can't teach an old mouse new clicks *

Dave Plowman London SW
To e-mail, change noise into sound.

Finding the keyboard operational
Bert entered:

Hello all
I have a few digital multimeters which are in need of calibrating,
cheap meters.
How do I make a DC calibrating voltage source with say 1% accuracy,
any voltage, prefer close to 1999 reading.
Thank you very much
Bert
Well if you have enough meters to make it worth your while, something like
Digikey part number MAX6012AEUR-TCT-ND would do it. True it's not near full
scale but better then a battery.
Bob

--�
--�
Coffee worth staying up for - NY Times
www.moondoggiecoffee.com

Finding the keyboard operational
Bert entered:

Hello all
I have a few digital multimeters which are in need of calibrating,
cheap meters.
How do I make a DC calibrating voltage source with say 1% accuracy,
any voltage, prefer close to 1999 reading.
Thank you very much
Bert
Well if you have enough meters to make it worth your while, something like
Digikey part number MAX6012AEUR-TCT-ND would do it. True it's not near full
scale but better then a battery.
Bob

--�
--�
Coffee worth staying up for - NY Times
www.moondoggiecoffee.com

Did download a few datasheets of MAX Reference voltage IC's
Will see what is available locally.
Thank you very much
Bert.