Volt / Ammeter

John Ammeter wrote:
Please, either change the subject title or quit this thread...

You know how you can be in a room filled with people all talking at once
but you'll instantly hear when someone mentions your name?? Well, I'm
getting tired of seeing my name posted every day on RAH...

How about changing the name of the thread to "ammeter"? At least, with
the lower case it isn't so obvious to me.

BTW, if you can believe it... I retired from the Meter Department of a
large public Electric Utility as the Crewchief for all
Commercial/Industrial Metering for our very large city.... I've had
enough references to my name and what I did to last several lifetimes....

John Ammeter

COLIN LAMB wrote:

I have been making shunts for years using a box of paper clips. I
measured the resistance of the full clip as .025 ohms, so part of a
clip is less resistance in a linear relationship. Larger paper clips
have less resistance. Depending upon the current drawn and the
sensitivity of the meter used, you may need to consider heat
dissipation and of course consider the insulation. I solder taps and
they work fine.

Far easier than using so many feet of wire.

Colin

John, you have nothing on my grade school shop teacher. His name was
....drum roll...Woody Rafters. Swear to God! And speaking of which, he
was the local Episcopal minister's son.

Rip

Montblack wrote:
("COLIN LAMB" wrote)
If we are talking about volt/amps with direct current, we could simply
replace the heading with watts and be done with it.


http://www.geocities.com/thereaganyears/environment.htm
James Watt... :-)


Montblack, a woman, two Jews and a cripple

Thank you Secretary Watt.

Dan, U.S. Air Force, retired

RST Engineering wrote:
Yeah, I'll give you that I missed the "powered from the measured voltage"
part. It becomes a bit less trivial. Practically impossible.

As for sticking pins through the wire a foot apart, you are going to get
more contact resistance (and corrosion as time goes on) than the shunt
itself. If you are using the primary wire as the shunt, I'd break the wire,
use a terminal strip with a shorter piece of thinner wire a few inches long,
then back to the larger wire.

Jim


"GeorgeB" wrote in message
...
On Thu, 16 Feb 2006 21:35:15 -0800, "RST Engineering"
wrote:

Yes, rather trivially.

Stick 2 pins through the
insulation about a foot apart and hook them to the meter.


Would AC amps and DC amps read the same given a single meter switched
between the two?

Dan, U.S. Air Force, retired

Paper clips? When Digikey has all these nice 3%, 0.005 to 0.10 current
sense resistors for $0.42?

"John Ammeter" wrote in message
news:5oidncI8B55FEmvenZ2dnUVZ_vidnZ2d@cablespeedwa .com...
I used to be known as "amprobe".... "probe" to my friends...

Probe

That would be milli amp probe, I would think! g

Jim Ducking and Running in NC

Would AC amps and DC amps read the same given a single meter switched
between the two?

Dan, U.S. Air Force, retired

G'day Dan,
they will normally read pretty close, but the meter (and you get what you
pay for...) will read an average of the applied AC or voltage.

This difference in reading will apply more to non-sinusoidal waveforms.

Some of the fancy meters will read "True RMS", but for most typical
applications a cheap meter will be close enough. To check the alternator
output in an aircraft....... Well, you could always log the data and apply a
calibration correction if you needed to be super-accurate.......

Hope this helps,
Peter

"John Ammeter" wrote in message
news:5oidncI8B55FEmvenZ2dnUVZ_vidnZ2d@cablespeedwa .com...
I used to be known as "amprobe".... "probe" to my friends...

Probe

That's pronounced Pro-bee as in Rookee or Newbee. . .

Rich "I knew someone at City Light" S.

"Rich S." wrote in message
news
"John Ammeter" wrote in message
news:5oidncI8B55FEmvenZ2dnUVZ_vidnZ2d@cablespeedwa .com...
I used to be known as "amprobe".... "probe" to my friends...

Probe

That's pronounced Pro-bee as in Rookee or Newbee. . .


I know, but I just couldn't pass on the obvious joke!
--
Jim in NC

On Fri, 17 Feb 2006 10:07:50 -0800, "RST Engineering"
wrote:

Yeah, I'll give you that I missed the "powered from the measured voltage"
part. It becomes a bit less trivial. Practically impossible.

As for sticking pins through the wire a foot apart, you are going to get
more contact resistance (and corrosion as time goes on) than the shunt
itself. If you are using the primary wire as the shunt, I'd break the wire,
use a terminal strip with a shorter piece of thinner wire a few inches long,
then back to the larger wire.

I'm wondering if the OP may have mis worded, or mis understood.

As you say the measurement is trivial, however I'm wondering if he
didn't think of powering the meter from the same source as was
*providing* the current rather than the current being measured. That
would make sense. Then it'd be easy and as you said, practically
impossible if powered from the *measured* current.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

Jim


"GeorgeB" wrote in message
.. .
On Thu, 16 Feb 2006 21:35:15 -0800, "RST Engineering"
wrote:

Yes, rather trivially.

Stick 2 pins through the
insulation about a foot apart and hook them to the meter.

"Roger" wrote in message
...
On Fri, 17 Feb 2006 10:07:50 -0800, "RST Engineering"
wrote:

Yeah, I'll give you that I missed the "powered from the measured voltage"
part. It becomes a bit less trivial. Practically impossible.

As for sticking pins through the wire a foot apart, you are going to get
more contact resistance (and corrosion as time goes on) than the shunt
itself. If you are using the primary wire as the shunt, I'd break the
wire,
use a terminal strip with a shorter piece of thinner wire a few inches
long,
then back to the larger wire.

I'm wondering if the OP may have mis worded, or mis understood.

As you say the measurement is trivial, however I'm wondering if he
didn't think of powering the meter from the same source as was
*providing* the current rather than the current being measured. That
would make sense. Then it'd be easy and as you said, practically
impossible if powered from the *measured* current.

What am I missing here? A good old fashioned analog ammeter is powered from
the "measured current".
Or, you can use a Simpson panel meter with your shunt. No power required. Of
course, they cost a fair bit of change nowadays.

http://www.simpsonelectric.com/pdf/w...-Vue%20ADC.pdf

You only need "power" if you want some kind of fancy pants digital readout.

--
Geoff
The Sea Hawk at Wow Way d0t Com
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