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Calibrating Volt Meters

G

Glenn jacobs

Jan 1, 1970
0
Anyone have any good ideas for acurate volatage sources, with out the need
for standards. My hope is to get accuracies to plus or minus 0.1 Volts.

JakeInHartsel
 
M

martin griffith

Jan 1, 1970
0
Anyone have any good ideas for acurate volatage sources, with out the need
for standards. My hope is to get accuracies to plus or minus 0.1 Volts.

JakeInHartsel
Do you mean
1V +- 0.1V thats 10%
or
100 +- 0.1V thats 0.1%


martin
 
G

Glenn jacobs

Jan 1, 1970
0
[4 quoted lines suppressed]
Do you mean
1V +- 0.1V thats 10%
or
100 +- 0.1V thats 0.1%


martin

Sorry should have been more clear. Plus or minus 30 Volts DC is the range
that I am interested in.

JakeInHartsel
 
A

AZ Nomad

Jan 1, 1970
0
Anyone have any good ideas for acurate volatage sources, with out the need
for standards. My hope is to get accuracies to plus or minus 0.1 Volts.

Or just use a random voltage source and an accurate meter to calibrate.
 
P

Paul E. Schoen

Jan 1, 1970
0
[snip]
Sorry should have been more clear. Plus or minus 30 Volts DC is the
range
that I am interested in.

JakeInHartsel

You will definitely need something that qualifies as a standard, although
you may not need laboratory grade instruments. For 0.3% accuracy you need a
standard about two or three times more accurate, or about 0.1%. Most DMMs
are at least that good, but you need to have it certified traceable to NIST
to be sure. You can buy 0.1% resistors, and build a divider from 30 VDC to
a commonly available standard voltage, such as 1.2 V or 2.5 V, but you will
need to make sure it is within the 0.1% accuracy. Then you would need a
sensitive galvanometer to determine that the voltage difference between
your standard voltage and the divider is zero. In this case you would need
about 2 mV resolution on the galvo. This is the old way to do it. A
certified DMM is the easiest, but certification costs about $40 or more.

Paul
 
R

Robert Baer

Jan 1, 1970
0
Glenn said:
Anyone have any good ideas for acurate volatage sources, with out the need
for standards. My hope is to get accuracies to plus or minus 0.1 Volts.

JakeInHartsel
I like the following voltage references, as i can use a box with 9V
batery compartment to run the part which sources or sinks current.
No need for a power switch due to the *very* low supply current, and
the 9V battery can run down to where it would be useless for anything else.
http://www.intersil.com/products/deviceresults.asp?i=14927

If you need 30V, then connect 6 of them in series using them as a
2-terminal shunt regulator (Vout and ground).
Or if you can stand the burning of more power and a higher supply
voltage, use one as the reference to an opamp that has a gain of six,
and use common 0.1% resistors (make sure that the supply voltage to the
reference is limited to spec).
 
I

Ignoramus10768

Jan 1, 1970
0
I believe that a well charged car battery is a quite accurate voltage
source, at about 12.68 volts or so. Am I mistaken?

i
 
A

AZ Nomad

Jan 1, 1970
0
I believe that a well charged car battery is a quite accurate voltage
source, at about 12.68 volts or so. Am I mistaken?
Yes.

It's barely accurate to a half volt.
 
N

Nico Coesel

Jan 1, 1970
0
Glenn jacobs said:
Anyone have any good ideas for acurate volatage sources, with out the need
for standards. My hope is to get accuracies to plus or minus 0.1 Volts.

I recently build a cheap +/- 10V reference using a 0.1% reference from
National, some 0.1% resistors and AD688 instrumentation amplifiers as
a buffer.
 
J

Jamie

Jan 1, 1970
0
Glenn said:
Anyone have any good ideas for acurate volatage sources, with out the need
for standards. My hope is to get accuracies to plus or minus 0.1 Volts.

JakeInHartsel
a fresh carbon cell was used in the old days.
i don't remember the the exact voltage but
something like 1.567 etc.

they do make reference diodes.
 
R

Richard Henry

Jan 1, 1970
0
Ignoramus10768 said:
I believe that a well charged car battery is a quite accurate voltage
source, at about 12.68 volts or so. Am I mistaken?

Yes
 
T

T. Atkin

Jan 1, 1970
0
martin griffith said:
Do you mean
1V +- 0.1V thats 10%
or
100 +- 0.1V thats 0.1%


martin

A mercury battery like PX675 (though may be kind of hard to find) loaded
with 1.5K resistor(1mA load) will give, if memory serves me, 1.348V. Very
precise. Four significative digits.

Tom
 
A

AZ Nomad

Jan 1, 1970
0
A mercury battery like PX675 (though may be kind of hard to find) loaded
with 1.5K resistor(1mA load) will give, if memory serves me, 1.348V. Very
precise. Four significative digits.

It isn't temperature dependent?
 
T

T. Atkin

Jan 1, 1970
0
AZ Nomad said:
It isn't temperature dependent?

Good point!
Here I'm not quite sure but the temperature only affects the battery
capacity, not its voltage.
I'm gonna investigate further.
On the other hand, my suggestion is not really a good one because production
of mercury cells has almost stopped.
 
A

AZ Nomad

Jan 1, 1970
0
Good point!
Here I'm not quite sure but the temperature only affects the battery
capacity, not its voltage.
I'm gonna investigate further.
On the other hand, my suggestion is not really a good one because production
of mercury cells has almost stopped.

Take that mercury battery, put a 5 1/2 digit meter on it and now you have
an accurate voltage source.
 
J

Jim Yanik

Jan 1, 1970
0
Most zeners are not stable and one would have to calibrate it and
put
it in a constant temperature oven and...
A number of *good* references have been mentioned that do not need
that kind of babysitting.

TEK video generators had a nice simple 2 transistor circuit for a temp oven
for their reference crystals,used a thermistor and a Darlington for the
heater.The whole thing fit in a little metal box about 2" square.
The oven will require some substantial amount of power,though,not really a
battery type of project.
 
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