1. Home
  2. General Electronics
  3. DC power meter suitable for a data logger?

DC power meter suitable for a data logger?

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

Reply to
Maury Markowitz
Loading thread data ...

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? 
--
   Wim Lewis , Seattle, WA, USA. PGP keyID 27F772C1
Reply to
Wim Lewis

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

Reply to
Maury Markowitz

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

Reply to
Jasen Betts

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

Reply to
Maury Markowitz

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 
address)

Experience: What you get when you don't get what you want
Reply to
DaveM

oduct,

Well this just moves the problem. I still need to actually measure the E and I.

Maury

Reply to
Maury Markowitz

product,

--- ???

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

(View in Courier):

+-----------------+-----------------------------------+ | | | | [R] LOGGER | [PV] | +-----+ | | +--+-------------------|Ein | | +-------|+\ | | | | | | | >--+---|--|--+----------------|Iin | | | +--|-/ | | | | +----+ | | [INVERTER] | | | | | +-|A | | | | [SHUNT] +--[R]---+ [R] | | AB|--[R]-+--|Pin | | | | | +----|B | | +-----+ | | [R] | +----+ [R] | | | | MULT | | +----+------------+-------------------+---------------+

JF

Reply to
John Fields

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.