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So... how do I wire it up for power?
1st off. If you plan on measuring the full output of a generator….you’ll need 2 of these. One for each hot leg.
With two of the meters, connect each one to one of the legs on a 240V breaker, like a sub-panel, water heater or dryer circuit.
 

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One very important thing to consider... For all the measurements to be valid, the meter needs to get power from the same lines it is measuring. So if the CT is clamped on to L1, the meter's power source should also be connected to L1 and its Neutral partner.

If you happen to have the CT on L1 and then the meter is powered from a separate source that might be on L2, about the only thing accurate will be the frequency (if L2 is also from the same generator) and current measurement from the CT for L1. All other parameters (wattage, voltage, pf, and kWh) will be wrong.
 

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Discussion Starter · #24 ·
Okay, I got the unit powered up and it's reading VAC and Hz. properly. I haven't been able to get the ring to pick up anything, but I'm probably not using it correctly. I tried to get readings from power cords, such as a cord to a lamp. There are no readings from that kind of cord for some reason. I have not tried to take any readings from the generators yet.
 

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One very important thing to consider... For all the measurements to be valid, the meter needs to get power from the same lines it is measuring. So if the CT is clamped on to L1, the meter's power source should also be connected to L1 and its Neutral partner.

If you happen to have the CT on L1 and then the meter is powered from a separate source that might be on L2, about the only thing accurate will be the frequency (if L2 is also from the same generator) and current measurement from the CT for L1. All other parameters (wattage, voltage, pf, and kWh) will be wrong.
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Makes me wonder.
Does the signal negate if the clamp is on both? It makes sense that it might, like some sort of signal balance when reading both. I was curious about that.
These work by sensing the AC current in the wire. If you put the coil across both wires it will cancel
Out. Your assumption is correct. Need to put the coil across only 1 of the 2 wires ( hot or neutral).
 

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Does the signal negate if the clamp is on both? It makes sense that it might, like some sort of signal balance when reading both. I was curious about that.
You could say that.

Do you ever see electricians use a clamp meter when they work on things like A/C compressor units? If you look closely, they only clamp one conductor to measure the current going through it. It's the same principle with your meter.
 

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yes. just one at a time on the conductor.
it is that magnetic field thing.
skin effect.
Gotta think back to my fundamentals in engineering to answer that one.

An AC current will create a magnetic field in the conductor its running through. Conversely, a changing magnetic field (AC magnetic field) will induce a current in an adjacent wire.
In this case…the hot wire from the generator is carrying AC current.
That AC current is creating an AC magnetic Field around the hot wire.
With the toroid is slipped over the hot wire, the AC magnetic field ( created from the AC current in the generator wire) is generating an AC current in the toroid wire.

The amplitude of the current in the toroid is proportional to the strength of the magnetic field ( from the hot wire of the generator) which in turn is proportional to the amplitude current that the generator is supplying.

While its simple physics…I honestly had to think about if for a few minutes as I haven’t thought about this since college!

Barring saturation of the magnetic field in the toroid, magnetic coupling and induction are very accurate ways of measuring current.

Oddly enough, the analog watt meters ( like the reliance ..pic in a post above) does not require the actual voltage from the circuit to measure power. I installed one a few years back on my generator setup and the only wires into or out of the meter is to connect the toriods that go over each hot leg. The little analog meters in the reliance watt meter are scaled t\to 120v so the power is directly proportional to current in the wire form the generator.

I don’t know if the digital watt meters work in the same manner of if they need the input voltage but if the intent is to measure the power from a home agenerator…then I’d presume that all of the power in the home would be from the generator so while there many be some voltage difference between eeach hot leg, the voltages should be close enough to get you a decent account of the power being drawn from each leg of the circuit.
So - if you have a single breaker available....youre going to be pretty close on total power. If you have a double breaker available to power each watt meter.......probably get more accurate yet again.
 

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If you only want a very rough approximation of the power being consumed by your load, sure, you can power the meter using the other leg of the 120V from the same generator. However, there’s also doing it right.

Here’s what’s said about taking current and voltage measurements from the same line...

From: https://www.geminidataloggers.com/info/energy-logger-power-factor
Some low end instruments only measure current and then assume that the voltage is fixed. They also assume that the power factor is 1.00, as they are not connecting to the voltage and comparing its timing with the current flow. Therefore this can present a very inaccurate picture of actual electricity usage. To present an accurate measurement of power usage, it is important to choose an energy logger that measures both voltage and current usage and correlates the timing between the two to measure the power factor.
We’re all familiar with the formula; W = VA x pf. If your V and pf are wrong and they don’t correlate to the current (A) being measured, your wattage along with Wh readings will also be wrong.

Just saying.
 

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If you only want a very rough approximation of the power being consumed by your load, sure, you can power the meter using the other leg of the 120V from the same generator. However, there’s also doing it right.

Here’s what’s said about taking current and voltage measurements from the same line...

From: https://www.geminidataloggers.com/info/energy-logger-power-factor


We’re all familiar with the formula; W = VA x pf. If your V and pf are wrong and they don’t correlate to the current (A) being measured, your wattage along with Wh readings will also be wrong.

Just saying.
Power factor isn’t a consideration in a residential scenario. Power factor (apparent power ) accounts for the phase angle of the current due to inductive loads that occur in industry. Think large industrial motors. Inductive loads cause current to lag voltage and in a plant where there are big inductive loads the Apparent power is considerable larger than the the calculated power and utilities need to compensate for the extra apparent power a plant draws. And while that’s an issue in an industrial plant ( and where the power company actually cares a out VA vs watts) it’s not an issue in a residential setting where the largest inductive load will be a fridge or a dryer….otherwise most loads are resistive where the PF is 1.
the reality is …if power factor was a concern residentially the utility companies would find a way to charge you for it. this has nothing to do with measuring voltage for a watt meter.
The windings on a generator are fixed together ( wound over each other ) and are almost wholly dependent on shaft speed for the voltage and frequency generated. The frequently between each leg is identical ( by nature of the windings overlaid ) and the voltage , while can vary by the load is also a function of the windings, which are overlaid. So the reality is. Unless you’re drawing a significant difference in current between each leg ( which is very possible ) the voltage difference will be minimal.
But. Open to opinion as my electrical trained is 30
Years dated.
power factor doesn’t matter.
 

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I welcome your opinion but I'm just all for accurate readouts and I can be pedantic about it. :)

IMO, it's hardly scientific to assume that the pf is negligible in a residential setting. I think the reason that power utilities doesn't penalize you is because in the grand scheme of things, residential homes does not account much of it compared to an industrial or commercial installation. However, in the context of running a generator at home (your personal power utility), it's reasonable to account for every Amp and Watt and so the pf plays a more significant role in the monitoring of your actual power usage.

Also, running inductive loads is not the only reason for having a poor pf. A lot of electronics and appliances are now running off of SMPS. These are non-linear loads and can reduce your circuit pf to as low as 0.6. The better but rare ones (with active pf correction) can only do around 0.8 to 0.9 pf on average. Granted, not every home is the same... but that's the more reason to take all of the variables into account.

When I put a meter to measure something, I owe it to myself to do it properly. Again, if all you care about is the Amperage going through a wire, power the meter from any power source. But this being a multi-function meter, the only proper way to connect it for the readouts to reflect the most accurate results, is to put it in-circuit of the lines being measured.
 

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led has to have some sort of power for the display.
and as stated in the other posts, try to keep the feed power the same leg as the amps coil.
that way you have a display for each leg eg L1 as volts / amp watts.

i do one step further the power switch as color coded.
black for L1 and red for L2 that way at a glance you know what leg you are on the readout.
just make sure the colors hold through your whole power system. 😆
 
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