AC DPM's -- are the all DPM'$?

D

David Lesher

Guest
I've been seeking some inexpensive AC digital panel meters; but
thus far, there's as hard to find as a popular BP executive.

Marel sells some that are $100 each, gulp.

Or is there a $6.95 AC-DC addon I can use on my pile of old DC
Analog Devices units?
--
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433
 
David Lesher <wb8foz@panix.com> wrote in news:hukp1i$eqq$1@reader1.panix.com:

I've been seeking some inexpensive AC digital panel meters; but
thus far, there's as hard to find as a popular BP executive.

Marel sells some that are $100 each, gulp.

Or is there a $6.95 AC-DC addon I can use on my pile of old DC
Analog Devices units?
Click to expand...
An op-amp with diodes? Fullwave rectifier.. Or even halfwave, on a single
supply. I don't know if anyone built those into complete sealed modules at
low cost though, I suspect people usually build their own.
 
David Lesher wrote:
I've been seeking some inexpensive AC digital panel meters; but
thus far, there's as hard to find as a popular BP executive.

Marel sells some that are $100 each, gulp.

Or is there a $6.95 AC-DC addon I can use on my pile of old DC
Analog Devices units?
Click to expand...

MPJA is currently out of stock, but they carry this for $8.95

http://www.mpja.com/prodinfo.asp?number=16177+ME

--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.
 
On Tue, 08 Jun 2010 03:31:20 -0400 "Michael A. Terrell"
<mike.terrell@earthlink.net> wrote in Message id:
<ho6dnYaRzONYbJDRnZ2dnUVZ_gGdnZ2d@earthlink.com>:

David Lesher wrote:

I've been seeking some inexpensive AC digital panel meters; but
thus far, there's as hard to find as a popular BP executive.

Marel sells some that are $100 each, gulp.

Or is there a $6.95 AC-DC addon I can use on my pile of old DC
Analog Devices units?


MPJA is currently out of stock, but they carry this for $8.95

http://www.mpja.com/prodinfo.asp?number=16177+ME
Click to expand...
These guys have stock, but you'll pay a bit more if you're in a hurry:
http://www.web-tronics.com/panelmeter.html
 
JW <none@dev.nul> writes:

MPJA is currently out of stock, but they carry this for $8.95

http://www.mpja.com/prodinfo.asp?number=16177+ME

These guys have stock, but you'll pay a bit more if you're in a hurry:
http://www.web-tronics.com/panelmeter.html
Click to expand...
Thanks. Those will do fine, but I guess I'll need separate
wallwart power supplies for each one. That, or isolation
transformers which will cost far more.

[Unless you have a spare 8-channel isolated power supply.]
--
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433
 
David Lesher wrote:
JW <none@dev.nul> writes:

MPJA is currently out of stock, but they carry this for $8.95

http://www.mpja.com/prodinfo.asp?number=16177+ME

These guys have stock, but you'll pay a bit more if you're in a hurry:
http://www.web-tronics.com/panelmeter.html

Thanks. Those will do fine, but I guess I'll need separate
wallwart power supplies for each one. That, or isolation
transformers which will cost far more.
Click to expand...

A 6.3 volt filament transformer, diode & electrolytic capacitor would
be a better choice. They are available wit a 1500 V isolation rating


--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.
 
"Michael A. Terrell" <mike.terrell@earthlink.net> writes:


Thanks. Those will do fine, but I guess I'll need separate
wallwart power supplies for each one. That, or isolation
transformers which will cost far more.

A 6.3 volt filament transformer, diode & electrolytic capacitor would
be a better choice. They are available wit a 1500 V isolation rating
Click to expand...
Not the issue. My point is, each one needs a separate supply. If I could
find very low current 277v primary xfmrs [I'm monitoring a 480 Y system];
then I could use one common supply. But such would be $$$ in quantity.



--
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433
 
David Lesher wrote:
"Michael A. Terrell" <mike.terrell@earthlink.net> writes:

Thanks. Those will do fine, but I guess I'll need separate
wallwart power supplies for each one. That, or isolation
transformers which will cost far more.

A 6.3 volt filament transformer, diode & electrolytic capacitor would
be a better choice. They are available wit a 1500 V isolation rating

Not the issue. My point is, each one needs a separate supply. If I could
find very low current 277v primary xfmrs [I'm monitoring a 480 Y system];
then I could use one common supply. But such would be $$$ in quantity.
Click to expand...

Some of the meters use isolated power inputs, You can always build a
simple DC to DC converter with multiple, isolated outputs. Then you can
use any reasonable DC voltage you have available for the input, or a
small transformer & diodes. It isn't rocket science.


--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.
 
"Michael A. Terrell" <mike.terrell@earthlink.net> writes:


Not the issue. My point is, each one needs a separate supply. If I could
find very low current 277v primary xfmrs [I'm monitoring a 480 Y system];
then I could use one common supply. But such would be $$$ in quantity.
Click to expand...

Some of the meters use isolated power inputs,
Click to expand...
I've not found same at good prices.

You can always build a simple DC to DC converter with multiple,
isolated outputs. Then you can use any reasonable DC voltage
you have available for the input, or a small transformer &
diodes. It isn't rocket science.
Click to expand...
Not sure where to find an xfmr with 6-8 identical windings...

I am thinking this would work. Find some old small B+
transformers. Use them to isolate and step down the 277V. Than
an appropriate resistor or two per meter, and a lower range on
the DPM would give me good data.
--
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433
 
David Lesher wrote:
"Michael A. Terrell" <mike.terrell@earthlink.net> writes:

Not the issue. My point is, each one needs a separate supply. If I could
find very low current 277v primary xfmrs [I'm monitoring a 480 Y system];
then I could use one common supply. But such would be $$$ in quantity.

Some of the meters use isolated power inputs,

I've not found same at good prices.

You can always build a simple DC to DC converter with multiple,
isolated outputs. Then you can use any reasonable DC voltage
you have available for the input, or a small transformer &
diodes. It isn't rocket science.

Not sure where to find an xfmr with 6-8 identical windings...
Click to expand...

A small inverter with a torroid output transformer. Wind your own,
it isn't that hard to do.


I am thinking this would work. Find some old small B+
transformers. Use them to isolate and step down the 277V. Than
an appropriate resistor or two per meter, and a lower range on
the DPM would give me good data.
Click to expand...

--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.
 
David Lesher wrote:
JW <none@dev.nul> writes:


MPJA is currently out of stock, but they carry this for $8.95

http://www.mpja.com/prodinfo.asp?number=16177+ME


These guys have stock, but you'll pay a bit more if you're in a hurry:
http://www.web-tronics.com/panelmeter.html


Thanks. Those will do fine, but I guess I'll need separate
wallwart power supplies for each one. That, or isolation
transformers which will cost far more.

[Unless you have a spare 8-channel isolated power supply.]
Click to expand...
Why do you need 8 separate supplies? You should be able
to run 8 (or N) of those DPMs from the same power supply
using the isolated ground configuration.

Ed
 
ehsjr <ehsjr@nospamverizon.net> writes:

http://www.mpja.com/prodinfo.asp?number=16177+ME
http://www.web-tronics.com/panelmeter.html

Why do you need 8 separate supplies? You should be able
to run 8 (or N) of those DPMs from the same power supply
using the isolated ground configuration.
Click to expand...
I'm less sure of that. I will be measuring 3 legs of 277VAC with them.
Less then good isolation could get....noisy...




--
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433
 
David Lesher wrote:
ehsjr <ehsjr@nospamverizon.net> writes:


http://www.mpja.com/prodinfo.asp?number=16177+ME

http://www.web-tronics.com/panelmeter.html


Why do you need 8 separate supplies? You should be able
to run 8 (or N) of those DPMs from the same power supply
using the isolated ground configuration.


I'm less sure of that. I will be measuring 3 legs of 277VAC with them.
Less then good isolation could get....noisy...
Click to expand...
Ok, I can't address how sure or unsure you are, but I can provide
some general information that may assist.

To understand their isolated ground, google on "virtual ground".
It should yield a _very_ high impedance (for practical purposes
you can consider it op amp input impedance) between the DPM's DC
supply and the input (the signal that is being measured) ground.

Also, this datasheet may help:
http://www.intersil.com/data/fn/fn3082.pdf

I guess, for you to be absolutely sure, you'd have to try it.
I have not done it with these DPM's myself.

Ed
 
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