DC power meter suitable for a data logger?

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I'm installing a multi-part solar PV system to do a head-to-head test
of three different panels. I'll gang the panels into an AC inverter
that I already have, and drive a test load of four 100 watt light
bulbs. My installer wants to grid-tie and pay for the data collection
at least, but I haven't made my way through the maze of local regs
yet.

Since the power is being ganged parallel into the inverter I'm going
to need to log upstream on the DC side. I'll likely end up with the
4-
channel HOBO (U12) as the basic collection system, but they don't
sell
a DC power meter.

Can anyone suggest a DC power metering solution with a suitable
output? The U12 supports "any third-party sensor with 4-20mA or 0 to
2.5 volt DC output".

Thanks!

Maury


Re: DC power meter suitable for a data logger?
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How much current are you expecting to measure? (Hmm, 400W at (wild guess)
48VDC = 8A total, 2-3A per panel?) Are you looking for an off-the-
shelf solution or a circuit?

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Re: DC power meter suitable for a data logger?
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About 150 to 250 W for the first install, adding another 75 or so when
the third panel goes up. VDC should be 12 to 25, I can wire parallel
or series into the inverter (although parallel strikes me as simpler
at first glance), so let's say 15 VDC at 10 amps.

Definitely need something off-the-shelf, the logger is going to be
positioned semi-protected so it will have to be well sealed.

Maury

Re: DC power meter suitable for a data logger?
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could you measure voltage and current separately and then combine the
results to get power? or is that going to fill up the data logger too
fast?

Bye.
   Jasen

Re: DC power meter suitable for a data logger?
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Absolutely, in fact that would be preferable. Although it's not
important to me, the voltage curves are very important for off-grid
battery-charging applications. Existing polysi panels are well
characterized in this regard, other technologies, not so much.

Maury

Re: DC power meter suitable for a data logger?
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Use an analog multiplier such as the AD835 or AD633 to provide the E*I product,
scale the output as appropriate and feed it to the logger.

--
Dave M
MasonDG44 at comcast dot net  (Just substitute the appropriate characters in the
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Re: DC power meter suitable for a data logger?
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Well this just moves the problem. I still need to actually measure the
E and I.

Maury

Re: DC power meter suitable for a data logger?
On Thu, 31 Jul 2008 14:18:48 -0700 (PDT), Maury Markowitz

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product,
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???

Use a voltage divider for the voltage and a shunt for the current.

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