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Test meter for wind turbine output Answered

Is there an inexpensive meter I can hook up to my 300W 12VDC wind turbine ?

I want to see the output power in watts increase as it spins faster. I know it needs a load to test that.

I know I can use 1 or more 12v bulbs to see them get brights. But I'd like to see the output in watts.

Thanks

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Jack A Lopez

1 year ago

Well, it seems to me, you think the answer to your power measuring problem, is going to be found in the form of a gizmo, a device, specifically a power meter.

We can imagine what such a gizmo would look like, right?

It would likely look like a little box with some sturdy connectors (maybe screw terminals?) for electrical inputs and outputs. Wires carrying power from a power source, go in one side. Wires carrying power to a load, exit the other side.

Most importantly it has a digital display, telling the user how much power it sees (feels? senses? calculates?), in some appropriate and understandable units, like watts, kilowatts, milliwatts, etc. Maybe it even has a timer, and it can integrate watts into joules, or watt*hours, for to tell you how much total energy has been transfered, over the course of a few minutes, hours, days, etc.

So where am I going with this story?

Well, such devices exist, but the trouble is that when you go shopping for a power meter, you have to pick one that is matched to the specific kind of electrical power you want to measure. E.g. AC or DC? What range of voltage and current?

Power meters for mains power, are pretty easy to find, e.g. for 120 volts AC, capable of measuring power over the range of around 20 to 2000 watts. The "Kill-a-Watt" brand meter, made by P3, is a good example of this

Also I have seen a USB power meter, for measuring power from a USB port (i.e. 5 volts DC, at current up to around 2 amperes or so, which is power of around 10 watts max). These are inexpensive, and the best place to find them is eBay.

If there is a 12 VDC, at currents up to 25 A, meter existing out there, my guess is that again the Chinese direct-to-eBay-sellers will have it for the best price.

Or you could build your own.

Or you could maybe just use two meters, one to measure voltage, one to measure current, and then multiply those two numbers together, to get an answer for power.

Or you could use a load with a predictable I-V curve, so that power dissipation could be inferred from just one measurement, of either voltage or current.

You know, the textbook example of a load with predictable I-V curve is a resistor, for which V = I*R, and dissipated power is,

P = V*I = V^2/R = I^2*R

By the way, resistors capable of dissipating 100s of watts of power, are out there. Or, possibly, you could build your own.

Or, you said you had a bunch of 12 volt light bulbs. Maybe you could measure the I-V curve for those. It will be an actual curve, you know, not a straight line like it is for a resistor. But if you knew that curve, then you would have a one-to-one map from voltage to power.