[time-nuts] Watts Up (was Re: Prologix GPIB/USB converter help...)

Neon John jgd at johngsbbq.com
Tue Apr 17 23:58:37 EDT 2007

On Tue, 17 Apr 2007 15:44:31 -0700, "Tom Van Baak"
<tvb at LeapSecond.com> wrote:

>> If you have the capability of testing your WUPs, I'd certainly be
>> interested in what you find.  I'd like to think that maybe the problem
>> is in just this one revision of firmware.  But I suspect not.
>> John
>Thanks much for your thoughts about the WUP. I might have
>guessed there were power-nuts out there! Very interesting.

I'm sure there are -nuts for just about everything.  Me, I collect
generators and inverters and utility equipment like you do cesium beam
clocks :-)  My only problem is that I have too many nut-isms for the
available funds....

>I guess I haven't worried about the power factor. What I do
>very much like about the WUP is the well-designed (and even
>documented) serial interface, the choice of command/response
>or periodic talk-only modes, and the clean design inside.

yes, that's what prompted me to buy one in the first place.  I was
doubly dismayed when I found the measurements to be junk.

>You can see some of my WUP power plots here:

Ya know, ever time I go to your site I get frustrated.  You seem to
get so much done and I have so much trouble getting anything done.
Age-related, I think, as I used to get things done too.

Anyway, for your electrical data, what are the red and black plots?
I'm guessing actual data and curve fitted respectively.

Also, are the utilities you list at the bottom of the page available

>I have not done much accuracy testing. For my lab, at
>this point at least, I'm much more concerned with power
>stability than accuracy. One of my big surprises was that
>none of my fancy UPS's give good power stability, so I'm
>migrating to "online" or "double conversion" UPS's which
>solve this problem.

I've been running my computers and some of the more sensitive
instruments like that for years.  Mine's homemade, a high current 12
volt supply, some AGM batteries and cheap inverters.  I really like
these converters:


I just bought another PD9280R for a project.  I like most all the
ChiCom inverters I've tested.  Power to Go is a good one.  So is the
2kw one that Harbor Freight has on sale right now.  All are "modified
sine" inverters but nothing I power minds the distortion.

>BTW, one digital power meter that I gave up on is:
>Would appreciate any comments you have on this.

I don't have any experience with that one.  My initial impression is
that they sure are expensive.

>The other power meters I'm using are by DMMetering.
>See eBay item 170102236411 and others by the same
>seller. These are 800 pulses per kWh and I log their
>data using a Newport/Omega iFPX internet counter:

That DMMetering unit looks slick.  I'm fighting off the urge to "buy
it now".  probably would have if it were anywhere other than
Sleazebay.  The Newport thing is also slick, though it seems a bit
expensive for the low count rate you're dealing with.  For low rates
like that I'm fond of banging the *ack line of a PC parallel port and
letting a bit of custom code I wrote service the interrupt and
accumulate counts.

Another company I'm fond of doing business with is this one:


I haven't tried their logging/control products yet but everything else
I've bought over the years has been very high quality for the money.

>I've monitored DC power with these two:
>RC Electronics, Watts UP WU100

I have a couple of these.  Nice little instruments.  I haven't done a
complete calibration check yet but the readings I've observed seem
reasonable.  I sure wish they'd quit infringing on the other Watts UP
trademark.  Very confusing when I try to recommend these instruments
to people.

>Medusa Power Analyzer II
>(yet another vendor that dropped RS232 for USB)

Looks like a DC Watts Up knockoff.  I'm like you, I REALLY dislike USB
on test instruments.  I recently bought one of these OXSL-689


I didn't think much of the USB interface.  I just figured they'd have
implemented it similar to an RS-232 interface.  Noooooo.  A crappy
windoze GUI program, no API and no command line utility.  I am greatly
annoyed, as I planned on using it with a pocket-PC.  I am not a happy

John De Armond
See my website for my current email address
Cleveland, Occupied TN
All great things are simple and many can be expressed in single words:
Freedom, Justice, Honor, Duty, Mercy, Hope.  -Churchill

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