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I'm trying to build an energy monitoring device following this guide

http://openenergymonitor.org/emon/buildingblocks/how-to-build-an-arduino-energy-monitor-measuring-current-only

enter image description here enter image description here Actual Image i hooked up the ct to a wire but doesn't seem to work.

I'm just hoping someone can find something wrong based on the picture...

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closed as unclear what you're asking by Scott Seidman, Ricardo, Daniel Grillo, Matt Young, PeterJ Feb 7 '15 at 1:40

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

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    \$\begingroup\$ Please provide a schematic diagram of at least the sensor connections. \$\endgroup\$ – Dwayne Reid Feb 6 '15 at 2:22
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    \$\begingroup\$ This is the diagram: openenergymonitor.org/emon/sites/default/files/… \$\endgroup\$ – thedjaney Feb 6 '15 at 2:43
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    \$\begingroup\$ When you say it doesn't work what result do you get, are all the readings not changing as current goes through the wire or something else? \$\endgroup\$ – PeterJ Feb 6 '15 at 6:38
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    \$\begingroup\$ I'm voting to close as unclear, as "doesn't seem to work" is not descriptive enough \$\endgroup\$ – Scott Seidman Feb 6 '15 at 14:00
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The 33 ohm burden resistor is calculated for 100A. If the the noise level is at about 2% of the scale, you wouldn't get a clear signal until you draw at least 4 or 5A. I'd recommend to use a different (higher value) burden resistor while testing on the bench.

I used the exact same circuit to detect current consumption of some pumps a few years ago. It definitely works, within reasonable limits. Don't expect 1% precision from it.

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Your connections as shown in the CAD drawing look good.

How often are you acquiring input samples? You are measuring an AC signal, so you need to be sampling that signal at a much faster frequency than the input signal.

I know that Nyquist says that you have to sample at least twice as fast as the input signal. However, accuracy will be poor. You want to be sampling the signal somewhere between 10 to 100 times faster than the input.

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  • \$\begingroup\$ I am actually sampling 1480 times and acquiring them every 1ms (also tried 1000ms). All I get is slightly fluctuating value that does not change even if I put an appliance in the AC. What I am least sure about what I am doing is the way I connect the clamp to the wire. It's just a simple extension wire with stranded core (not sure if it matters). \$\endgroup\$ – thedjaney Feb 6 '15 at 4:00
  • \$\begingroup\$ I guess you could rectify to direct current and average using a capacitor, and calculate assuming a RMS figure. But 33ohms is a pretty low impedance load. \$\endgroup\$ – Vitim.us Feb 6 '15 at 4:23
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    \$\begingroup\$ Question: are you treating the values above and below your reference voltage as signed numbers? That is: a voltage below the reference is negative and a voltage above the reference is positive. \$\endgroup\$ – Dwayne Reid Feb 6 '15 at 4:30

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