Watt meter

J

Jessica Shaw

Guest
Hi,

I am consider to use one of the following watt meter. My question is
which one can have more capability to handle large currents and
voltages. Which one is better? I know they are old but I have to chose
between one of them.

1. http://my.ebay.com/ws/eBayISAPI.dll?MyEbay&gbh=1&CurrentPage=MyeBayWon&ssPageName=STRK:ME:LNLK:MEWNX


2. http://www.kjq.us.com/images/SIMPSON_880_WATT_METER.pdf


Thanks

Jess
 
"Jessica Shaw"
I am consider to use one of the following watt meter. My question is
which one can have more capability to handle large currents and
voltages. Which one is better? I know they are old but I have to chose
between one of them.

1.
http://my.ebay.com/ws/eBayISAPI.dll?MyEbay&gbh=1&CurrentPage=MyeBayWon&ssPageName=STRK:ME:LNLK:MEWNX
Click to expand...
** Not viewable.

Post a direct link to the sale.
 
<jsscshaw88@gmail.com>

One thing that I forgot to mention that can these wattmeters work with
100KHz signals.
Click to expand...

** Definitely NOT.


..... Phil
 
One thing that I forgot to mention that can these wattmeters work with 100KHz signals.

Thanks
jess
 
Jessica Shaw wrote:
Hi,

I am consider to use one of the following watt meter. My question is
which one can have more capability to handle large currents and
voltages. Which one is better? I know they are old but I have to chose
between one of them.

1. http://my.ebay.com/ws/eBayISAPI.dll?MyEbay&gbh=1&CurrentPage=MyeBayWon&ssPageName=STRK:ME:LNLK:MEWNX
Click to expand...

There is no item number in that link. It is only veiwable from your
account.


Post it like this:

http://www.ebay.com/itm/xxxxxxxxxxxxx

by replaing the string of x with the item number to give you alink like
this:


http://www.ebay.com/itm/1320775125643


Just copy & paste it over the row of x's
 
jsscshaw88@gmail.com wrote:
One thing that I forgot to mention that can these wattmeters work with 100KHz signals.
Click to expand...

The Simpson meter is only calibrated for 60 Hz loads. The inductance
in the metering circuit is way too high for 100 KHz.
 
<jsscshaw88@gmail.com> wrote in message
news:73224b8c-db65-45d2-a841-9739f21bd82d@googlegroups.com...
One thing that I forgot to mention that can these wattmeters work with
100KHz signals.

Thanks
jess
Click to expand...
You're looking at silly money for one that will do that - in days gone by,
such wattmeters used a device which combined a filament lamp & thermocouple
in the same envelope, some of those were good up to RF.

Unless you're filthy-rich, you may need to look at home made - at least one
hobby magazine has published a design that uses modern solid state measuring
chips to determine power in a load - IIRC it may have been Elektor, and
there's probably at least a PCB available from readers services - if not a
full kit.
 
"Ian Field"

You're looking at silly money for one that will do that - in days gone by,
such wattmeters used a device which combined a filament lamp &
thermocouple in the same envelope, some of those were good up to RF.
Click to expand...

** That describes a " True RMS Voltmeter" - not a wattmeter.


.... Phil
 
On Friday, July 27, 2012 12:52:57 PM UTC-7, (unknown) wrote:
One thing that I forgot to mention that can these wattmeters work with 100KHz signals.
Click to expand...
You can calibrate them to work. That doesn't make
them precise, however.

For 100 kHz signals, I'd use an analog multiplier, or a two-channel
digital oscilloscope and some math. The input impedances of
your current and voltage probes, of course, have to be compensated.
 
On Sat, 28 Jul 2012 15:51:26 -0700, whit3rd wrote:

or a two-channel
digital oscilloscope and some math. The input impedances of your current
and voltage probes, of course, have to be compensated.
Click to expand...
That's the way I measure power factor. You need a digital 'scope that
multiplies and integrates.

RMS volts * RMS current = apparent power.

Per sample volts * per sample current, integrated over a cycle = true
power.

--
"For a successful technology, reality must take precedence
over public relations, for nature cannot be fooled."
(Richard Feynman)
 
"Fred Abse"
RMS volts * RMS current = apparent power.

Per sample volts * per sample current, integrated over a cycle = true
power.
Click to expand...

** Two more for completeness:

1. RMS voltage squared / resistance = true power.

2. RMS current squared x resistance = true power.

Important to check that over the frequency range of interest, the
resistance value is constant.

Also, the wave must be cyclic and non varying over the test period.

Plus any DC component must be included in the RMS value.



.... Phil
 
"whit3rd" wrote in message
news:f2d6f52c-2316-4399-9e16-e40ff253c2b8@googlegroups.com...

For 100 kHz signals, I'd use an analog multiplier, or a two-channel
digital oscilloscope and some math. The input impedances of
your current and voltage probes, of course, have to be compensated.
Click to expand...
A log/antilog amplifier circuit can be used for a multiplier:
http://www.electronics.dit.ie/staff/ypanarin/Lecture%20Notes/DT021-4/6LogAntiLogAmplifiers.pdf

Another method that works from 1kHz to over 1 GHz:
http://te.ugm.ac.id/~risanuri/elan/OTA-Based%20High%20Frequency%20CMOS%20Multiplier%20and%20Squaring%20Circuit_Ispacs.pdf

There's an RF wattmeter kit here for $55 (and some other interesting items):
http://www.qsl.net/k/k5bcq/Kits/Kits.html

And you can probably use something like the dsPIC30F2010 which has six
10-bit 500 kS/sec ADCs
http://ww1.microchip.com/downloads/en/devicedoc/70118e.pdf

Paul
 
On Mon, 30 Jul 2012 11:29:26 +1000, Phil Allison wrote:

* Two more for completeness:

1. RMS voltage squared / resistance = true power.

2. RMS current squared x resistance = true power.

Important to check that over the frequency range of interest, the
resistance value is constant.

Also, the wave must be cyclic and non varying over the test period.

Plus any DC component must be included in the RMS value.
Click to expand...
Quite so.

--
"For a successful technology, reality must take precedence
over public relations, for nature cannot be fooled."
(Richard Feynman)
 
Phil Allison Inscribed thus:

"Ian Field"

You're looking at silly money for one that will do that - in days
gone by, such wattmeters used a device which combined a filament lamp
& thermocouple in the same envelope, some of those were good up to
RF.


** That describes a " True RMS Voltmeter" - not a wattmeter.


... Phil
Click to expand...
What Jessica needs is a "Bolometer" ! Though I haven't seen one for many
years. They look a little like the old 954 acorn valve.

--
Best Regards:
Baron.
 
On 2012-08-01, Baron <baron@linuxmaniac.net> wrote:
Phil Allison Inscribed thus:


"Ian Field"

You're looking at silly money for one that will do that - in days
gone by, such wattmeters used a device which combined a filament lamp
& thermocouple in the same envelope, some of those were good up to
RF.


** That describes a " True RMS Voltmeter" - not a wattmeter.


... Phil

What Jessica needs is a "Bolometer" ! Though I haven't seen one for many
years. They look a little like the old 954 acorn valve.
Click to expand...
ITYM a calorimeter


--
⚂⚃ 100% natural
 
Jasen Betts Inscribed thus:

On 2012-08-01, Baron <baron@linuxmaniac.net> wrote:
Phil Allison Inscribed thus:


"Ian Field"

You're looking at silly money for one that will do that - in days
gone by, such wattmeters used a device which combined a filament
lamp & thermocouple in the same envelope, some of those were good
up to RF.


** That describes a " True RMS Voltmeter" - not a wattmeter.


... Phil

What Jessica needs is a "Bolometer" ! Though I haven't seen one for
many years. They look a little like the old 954 acorn valve.

ITYM a calorimeter
Click to expand...
Yes you're probably right. It must be 45-50 years since I used them to
measure RF power. Tiny little things, died at the drop of a hat. :)
About 20mw was the most they could handle. I've probably still got
some hiding, in all the junk I should really throw out...

--
Best Regards:
Baron.
 
Baron wrote:
Jasen Betts Inscribed thus:

On 2012-08-01, Baron <baron@linuxmaniac.net> wrote:
Phil Allison Inscribed thus:

"Ian Field"

You're looking at silly money for one that will do that - in days
gone by, such wattmeters used a device which combined a filament
lamp & thermocouple in the same envelope, some of those were good
up to RF.

** That describes a " True RMS Voltmeter" - not a wattmeter.


... Phil
What Jessica needs is a "Bolometer" ! Though I haven't seen one for
many years. They look a little like the old 954 acorn valve.
ITYM a calorimeter


Yes you're probably right. It must be 45-50 years since I used them to
measure RF power. Tiny little things, died at the drop of a hat. :)
About 20mw was the most they could handle. I've probably still got
some hiding, in all the junk I should really throw out...

I used a bolometer mounted in a waveguide to measure power at X-band
Click to expand...
back in 1949. They couldn't take much more than a 50% overload without
burning out and calibrating was tricky!

--
Virg Wall, P.E.
 
On 2 Aug 2012 12:01:17 GMT, Jasen Betts <jasen@xnet.co.nz> wrote:

On 2012-08-01, Baron <baron@linuxmaniac.net> wrote:
Phil Allison Inscribed thus:


"Ian Field"

You're looking at silly money for one that will do that - in days
gone by, such wattmeters used a device which combined a filament lamp
& thermocouple in the same envelope, some of those were good up to
RF.


** That describes a " True RMS Voltmeter" - not a wattmeter.


... Phil

What Jessica needs is a "Bolometer" ! Though I haven't seen one for many
years. They look a little like the old 954 acorn valve.

ITYM a calorimeter
Click to expand...
---

http://en.wikipedia.org/wiki/Calorimeter

So, no.

http://en.wikipedia.org/wiki/Bolometer

http://www.hparchive.com/Manuals/HP-475B-Manual-sn-11.pdf

http://www.ebay.com/sch/sis.html?_nkw=HP%20BOLOMETER%20MOUNT%20M%20476A%20W1%20&_itemId=170504419653

So, yes.

--
JF
 
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