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 Post subject: Optical Probe for Net Meters?
PostPosted: Fri Feb 08, 2008 2:23 am GMT EthGMT 
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Fish Eggs
Fish Eggs

Joined: Thu Feb 07, 2008 8:18 pm GMT EthGMT
Posts: 2
I did a bit of web searching a couple months ago in an attempt to determine the interface of an optical probe to communicate with the net meter on my house. I found a reference to someone who had requested and received access to the meter from PG&E, but I've been unable to get any more information from this person. Has anyone here attempted to do this? The main benefit I see to this over monitoring the inverter is that you can get the full picture, both consumption and generation.

I tried getting some help from the company that designed and installed the system ... if they had done it they weren't telling me about it ...

I found that the probes are very expensive to purchase, but I saw some talk of a DIY version.

TIA!
Steve

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Steve B
San Jose, CA
Day4Energy/Xantrex GT System


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 Post subject:
PostPosted: Fri Feb 08, 2008 5:23 pm GMT EthGMT 
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Guppy
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Joined: Wed Apr 19, 2006 1:02 am GMT EthGMT
Posts: 110
Location: SF Bay Area
About the best I have seen talked about so far is, for example, my PG&E "GEH-7285, kV2c Encompass Electronic Meter" outputs 25 mSec pulses every so often when not connect to the IR comm interface:

Quote:
The OPTOCOM LED emits calibration pulses (infrared light) until the meter detects the presence of OPTOCOM communications. This LED is the source of Watthour and VArhour calibration pulses. Each calibration pulse is equal to the value assigned to Kt (Watthours or VArhours). The duration of each output pulse is approximately 25 milliseconds.


"kT" seems to default to one rotation of the meter rotor (or electronic LCD rotor in this case).

Unfortunately, it appears that one cannot tell the direction of rotation for the rotor--so for Net Metered TOU installations (like my home), it appears to be useless.

It might be worth putting an O'scope on the IR output and see if one can see the difference between "left" and "right" rotation... But I doubt it.

Another way would be for a couple of devices to "read" the LCD bar display for direction and count (example 1 rotation = 3 Whours)...

But would it be worth it? Would your local utility have a cow if they saw a bunch of sensors/optics glued to the face of your meter and send you a nasty letter trying to figure out if you are tampering with their $$$$?

Get two used meters, one for the "inverter" and one for the whole house load with metering pulse outputs (I believe some of the mechanical meters have this option). Then run the two (unidirectional inputs) to your computer and totalize from there... Or scrap the meter for the inverter and use the RS232 (or whatever interface) for its logging.

-Bill


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