# Picked Up A LCD Meter, Need Advice



## LaSwamp (Mar 16, 2021)

Hi Guys. I picked up an item I've had my eye on for a while. Now I'm unsure how to get it working. 










I saw some of you have this and it flung a craving on me. I'm not sure how to wire it. It has 4 terminals which I presume is for the ring sensor and some kind of power input. Below is a diagram but I'm not sure what it means. How does the unit get power? And what's the light bulb all about? 










It looks like the top and bottom screws are hot and the two in the middle are neutral? Am I reading that right? 

Looks like a really cool little unit, if I can figure out how to use it.


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## OrlyP (Oct 19, 2021)

The top two wires are for the current transformer (CT), which is included in the package. The CT is looped around the hot wire going to the load side and which the current you want measured.

The bottom two wires provides AC power to the monitor, where it also samples the voltage, frequency, and together with the current read by the CT, allows it to compute the wattage, energy consumption, and power factor. 

I use something similar mounted on a DIN rail.... similar wiring setup.


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## drmerdp (Apr 10, 2018)

I have 2 of that same monitor la swamp. I have one complaint with that unit. If it mounted on a wall above or below your eye line the screen is difficult to read. But the split CT makes it a bit easier to install.


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## LaSwamp (Mar 16, 2021)

So... how do I wire it up for power? Do I just use a power cord with bare leads? I can't tell polarity from the diagram, unless red is hot or it doesn't matter. 

I'm looking forward to trying it out. I figured it would be good for when I'm running on generator power.


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## OrlyP (Oct 19, 2021)

For my use case, I use it to monitor the output from the generator while the CT is looped around one of the AC wire from the generator. So the meter is only active while the generator is running.

In the diagram you provided, just replace the outlet/receptacle with the generator and the light bulb with the load side going to your home.

For all intents and purposes, the meter just taps to your existing wiring. Hot and Neutral orientation won't matter with this meter. Even the CT can be clamped on either Hot or Neutral... it will still work the same way. But for illustration, I assumed red to be Hot and blue to be Neutral. I think some consistency is in order. The CT is is non-polarized so I colored both wires black and it can be clamped any which way you want.

In the diagram, it's measuring the current passing through the Hot (red) wire.


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## iowagold (Jan 22, 2020)

make sure to use an bakolite inline glass fuse holder with a 1 amp @ 250 vac glass fuse on the power feed for this unit.
pm if you need details on the wiring.
i like to use 4 of the meters.
one set for the L1 and L2 on the grid or line side
and one set for the generator L1 and L2

and place an inline switch for the power feed after the fuse holders so you can turn off the display to save life on the display.

i also use led power indicators after the fuse holders as lights to indicate if the grid has power as well as the gen feed.
it makes checking things easy at a glance and a couple of flicks of switches.

and it sure helps to see the load as well as the voltage at the same time all at a glance.
i like the meters on top of the interlock breaker panel in a hoffman box.
pm for the build instructions.


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## OrlyP (Oct 19, 2021)

Agreed. Forgot about L1 and L2. 

We don't normally have two 120V leg outputs, just a single 220V leg.


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## LaSwamp (Mar 16, 2021)

For portability, would it be possible to use a cord with a standard 120 VAC plug rather than hard-wiring it onto a specific generator? I'm presuming the unit will run off of a 120 VAC source?


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## OrlyP (Oct 19, 2021)

There are 1,001 ways to skin a cat.

If you're monitoring anything that doesn't use up more than 15A on a single 120V leg, you can make do with a Kill A Watt.

Otherwise, you will need to build a box for the 6-in-1 power monitor. It can be installed in-circuit (ie. appropriate plug, cable, and receptacle built-in) that you insert between the generator and the load, or probably something like in the video below.


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## LaSwamp (Mar 16, 2021)

I was shooting for a less permanent way to mount the unit. Does the unit itself run on 120 VAC? If it does, would getting a small power cord from the hardware store work for providing power to the unit? It seems like that would work.


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## OrlyP (Oct 19, 2021)

Yes. Acceptable input voltage is written on the back: 80-260V AC.


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## drmerdp (Apr 10, 2018)

As mentioned if you planning to monitor current from a standard household 5-15/5-20 outlet a killawatt is a much easier plan. If you are planning to monitor the a 30amp 120v or 30 amp 120/240v connection you’ll need a box to house the monitor(s) with appropriate connectors to place the box in line with the power cord. 

Just for reference what I built to house it.


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## iowagold (Jan 22, 2020)

just make sure to use an 1 amp inline fuse for each cord.
the meters do not have fuse protection.


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## cosmic (Jul 1, 2021)

LaSwamp said:


> Hi Guys. I picked up an item I've had my eye on for a while. Now I'm unsure how to get it working.
> 
> View attachment 10498
> 
> ...


Yeah, what they said, I think..
Now I'm really confused.
Doesn't bthe kil a watt just plug in and then you just plug in whatever appliance you're trying to monitor ?

Cause I would really like to know what this refrigerator is using with all the action going inside, defrost, icemaker etc, not just the max amps for the compressor. 
I'll keep following here......


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## macdenewf (Sep 3, 2021)

LaSwamp said:


> So... how do I wire it up for power? Do I just use a power cord with bare leads? I can't tell polarity from the diagram, unless red is hot or it doesn't matter.
> 
> I'm looking forward to trying it out. I figured it would be good for when I'm running on generator power.


I happened to have 2 of these sitting in my fun drawer and broke them out when my neighbor was connecting up his generator. 
1st off. If you plan on measuring the full output of a generator….you’ll need 2 of these. One for each hot leg. Then manually add up the power from each leg for the total power. What’s good about seeing each leg is you can easily imbalance a generator depending on what 120v loads are connected. All the 240 loads balance them selves as they pull from each leg. Anyway. With 2 installed you can see what each side of your panel is drawing. 

im Uncertain of your setup but we installed the units close to the electrical panel where the coils could be installed over the hot legs coming in from the generator inlet plug.
Went to Home Depot and found a double gang metal box that both of them could fit in and make a cover from some flat plastic to fit the gang box. 

These do have to be powered so we pulled the power from a spare 120 volt breaker he had in the panel. 

Technically speaking if you wanted to be really picky you could power each from the same side of the panel as where you pull power using a double pole breaker which would show you the voltage of each leg separately but that’s kind of overkill. Would have to assume that a reasonably balanced generator load would have equal voltage per leg. 
If he was home I’d walk over and grab a few pictures. But. Away for TG. 

if you want a non powere version. Reliance sell a watt meter fir a generator . 2 coils and a analog meter but works great…though more expensive than the option you’re looking at…even when you need 2 of them.


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## macdenewf (Sep 3, 2021)

macdenewf said:


> I happened to have 2 of these sitting in my fun drawer and broke them out when my neighbor was connecting up his generator.
> 1st off. If you plan on measuring the full output of a generator….you’ll need 2 of these. One for each hot leg. Then manually add up the power from each leg for the total power. What’s good about seeing each leg is you can easily imbalance a generator depending on what 120v loads are connected. All the 240 loads balance them selves as they pull from each leg. Anyway. With 2 installed you can see what each side of your panel is drawing.
> 
> im Uncertain of your setup but we installed the units close to the electrical panel where the coils could be installed over the hot legs coming in from the generator inlet plug.
> ...


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## plannersteve (Nov 20, 2021)

LaSwamp said:


> I was shooting for a less permanent way to mount the unit. Does the unit itself run on 120 VAC? If it does, would getting a small power cord from the hardware store work for providing power to the unit? It seems like that would work.


You don't need any power cord for this meter. It is powered by the circuit where you are installing it. What specifically are you trying to do? Connect to the power outlet of your generator? .


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## plannersteve (Nov 20, 2021)

LaSwamp said:


> I was shooting for a less permanent way to mount the unit. Does the unit itself run on 120 VAC? If it does, would getting a small power cord from the hardware store work for providing power to the unit? It seems like that would work.


Maybe this makes it clearer. Here is an example of one I installed in a disconnect box to measure power consumption for a heat pump.


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## macdenewf (Sep 3, 2021)

plannersteve said:


> You don't need any power cord for this meter. It is powered by the circuit where you are installing it. What specifically are you trying to do? Connect to the power outlet of your generator? .


That’s not quite correct. You do have to power it. The hot line from the generator runs through the coil but that is only to measure the current draw. You still need to power the digital circuit. Clearly the power will come from the generator but you do have to connect to 120 ( hot and neutral ) somewhere.


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## plannersteve (Nov 20, 2021)

macdenewf said:


> That’s not quite correct. You do have to power it. The hot line from the generator runs through the coil but that is only to measure the current draw. You still need to power the digital circuit. Clearly the power will come from the generator but you do have to connect to 120 ( hot and neutral ) somewhere.


True, it is powered. Maybe I misunderstood the OP, but he seemed to question if he needed to get a cord from the hardware store and plug it into an outlet somewhere.


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## macdenewf (Sep 3, 2021)

plannersteve said:


> True, it is powered. Maybe I misunderstood the OP, but he seemed to question if he needed to get a cord from the hardware store and plug it into an outlet somewhere.


That could work too but if recessing in the wall id pull the power from the panel.


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## tabora (Sep 6, 2018)

LaSwamp said:


> So... how do I wire it up for power?





macdenewf said:


> 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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## OrlyP (Oct 19, 2021)

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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## LaSwamp (Mar 16, 2021)

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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## OrlyP (Oct 19, 2021)

Put the CT clamp on one conductor only... usually on the hot wire, not on both of them.













__





Learn | OpenEnergyMonitor







learn.openenergymonitor.org


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## LaSwamp (Mar 16, 2021)

OrlyP said:


> Put the CT clamp on one conductor only... usually on the hot wire, not on both of them.
> 
> 
> 
> ...


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.


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## macdenewf (Sep 3, 2021)

OrlyP said:


> 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.


. 
Makes me wonder.


LaSwamp said:


> 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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## OrlyP (Oct 19, 2021)

LaSwamp said:


> 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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## iowagold (Jan 22, 2020)

LaSwamp said:


> 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.


yes. just one at a time on the conductor.
it is that magnetic field thing.
skin effect.


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## macdenewf (Sep 3, 2021)

iowagold said:


> 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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## OrlyP (Oct 19, 2021)

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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## macdenewf (Sep 3, 2021)

OrlyP said:


> 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...
> 
> ...


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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## OrlyP (Oct 19, 2021)

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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## iowagold (Jan 22, 2020)

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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## j.boudreaux88 (Oct 25, 2021)

plannersteve said:


> Maybe this makes it clearer. Here is an example of one I installed in a disconnect box to measure power consumption for a heat pump.


How's this possible?


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## GenKnot (Dec 20, 2021)

j.boudreaux88 said:


> How's this possible?


Not sure what your question is. Does the photo attached to that comment help? The photo shows how to correctly wire it.


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## j.boudreaux88 (Oct 25, 2021)

GenKnot said:


> Not sure what your question is. Does the photo attached to that comment help? The photo shows how to correctly wire it.


Yes, however it's a single wire reading a 240 volt current. I'm asking how that is possible due to my understanding of those meters, and limited familiarity with how 240v can be wired, since I've never seen a single wire 240v set up before.


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## GenKnot (Dec 20, 2021)

With 240 volt you only have to measure the current in one leg and then multiply by 240 volts to get the Watts


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## GenKnot (Dec 20, 2021)

@j.boudreaux88 Maybe what is confusing you is that the load in post #18 is a 240V unit. Therefore, the two hot legs are balanced and the neutral does not carry any current.

If that meter was connected to a panel for example, then there may be mixed 120V loads and 240V loads. The two hot legs would not necessarily have balanced current. Two meters would be required in that instance...one for each leg.


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## OrlyP (Oct 19, 2021)

j.boudreaux88 said:


> Yes, however it's a single wire reading a 240 volt current. I'm asking how that is possible due to my understanding of those meters, and limited familiarity with how 240v can be wired, since I've never seen a single wire 240v set up before.


Yeah, to get to 240V, you will have to measure across the two Hots (120V x 2). As Genknot mentioned, if you want to measure the current across the 240V line (assuming everything is balanced), you can put the CT across either Hots.

But for a typical US home where the great majority of appliances are 120V, you will have to put two meters. Both voltage and current measurements are taken from each Hot leg to Neutral.


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