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Is there an easy way to tell if a unit is pure sine wave vs modified?

Wiley

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OK, so I bought a pig in a poke and I knew that went I went in but the price was good and so I thought I would take the chance.
Here's the item although I bought from a different seller.... Walmart who had it on clearance at $65. Walmart's return policy is easy and so I took the chance.


My Xantrex X Power 1000 Watt died (no known reason... just ceased working) and I figured if a known name can leave me stranded then I really I'm not getting much in the way of reliability for paying significantly more. Pretty cynical perhaps but a great deal of this stuff is near FM to me anyway. I checked the internal fuses and they are fine and nothing looks burned or otherwise damaged.

So the unit has arrived and it seems to work well, and it runs power tools: grinder, shop vac etc without problem . The voltages it gives for the battery and output are very close to what my meter reads (but of course that too is made in China, but it has worked well for a good many years).

The inverter came in a box which had some portion of the printing erased off. Lots of different products apparently fit in this box. The printing has a selection of input and output boxes available to be checked and the ones fitting what I purchased were correctly checked. However, nothing about watts were listed. There is a very basic instructions which gave no specifications or maker. There is nothing written on the unit itself (save for: on/off; power; fault; DC; AC; AC110V and FAN).

So my question: Is there an easy way to determine if it is true sine wave other than using an oscilloscope?
Many thanks, Wiley
 
I am interested to know as well. Likely an old TV set would show junk on screen if it was modified...

I wonder what that unit will put out. Probably only around 800 watts constant. It might be worth it to take it somewhere that has an oscilloscope to check it’s output.
 
There's a thread on here about induction cook tops and modified sign wave inverters not getting along very well. If you have one of those, you could try that. Some computer power supplies also hum when on a modified sign wave inverter, but there's no good way to tell which ones will, vs not.
 
Plug a box fan or osculating fan into it. If it's a modified Sine Wave, it will usually hum and not be as strong (RPM's) compared to plugging it into utility power. Compare the difference.

The price seems too good to be true for a Pure Sine Wave Inverter. For a 3000 Watt Pure Sine Wave Inverter, prices average around $270 USD or more.
 
Morth thanks, but we cook on gas. Thanks for the suggestion Delta-V, I have a box fan. It's a three speed model nothing fancy but actually made in USA. I first checked speed and sound on a house circuit and then on this inverter. I could detect no difference either in speed/forcefulness of the fan on any speed setting and there was no hum. The fan is not quiet so maybe there's something buried in the noise it makes but certainly nothing dramatic. The inverter stepped up its cooling fans in direct relation to the load so it seems to have an idle and under load modes.

As an up date, I also had occasion to speak with my brother tonight. He's an old guy like myself but during his working years was a test engineer for Atari, way back when dinosaurs stalked silicon valley. He said: "Yes, he has a oscilloscope set up but the bench is cluttered yada yada yada. So why don't I look into a pocket oscilloscope? They aren't expensive and you might find it useful." I didn't know such things existed. But I checked online and now have on order a very, very small pocket oscilloscope, charges off USP and with 10 x probe and adapter can test up to something like 600 volts AC and has something over 200 five star reviews and like 9 four star... nothing lower. Its cost including shipping: $33.33. So in several weeks I'll know for sure whether or not it is pure sine wave or simply modified sine wave.
Again I have no connection except I shop there: here's a link in case anyone was curious:
 
Plug a box fan or osculating fan into it. If it's a modified Sine Wave, it will usually hum and not be as strong (RPM's) compared to plugging it into utility power. Compare the difference.

The price seems too good to be true for a Pure Sine Wave Inverter. For a 3000 Watt Pure Sine Wave Inverter, prices average around $270 USD or more.
Don’t compare that unit to a 3000 watt inverter... realize it is a 3000watt peak... so, likely rated at 1500, or less... probably 750.
 
Supervstech, Absolutely! I will be quite happy if the unit handles 1000 watts on a sustained basis. The advert says 1500 sustained so I'm hoping for 1000. I was looking for a unit to power my home theater when the power goes out. At present I would fire up the generator and we would retire to the theater to spend the evening watching movies or even TV. And although the generator thru the transfer switch also powers the freezers, frigs, and septic pump (system that only runs short intervals four times a day at max) IMHO I think running the generator (5kw diesel) a huge waste of energy save for when one has power applications. Thus my quest for a simple solar setup to power the theater and perhaps a few light circuits. Since I live where solar is only viable (IMHO) for five or six months a year trying to create a "whole house" solar system makes little sense to me.
Generators for power applications; solar for lights and entertainment (when the season allows) and for long sustained outages during non solar times: kerosene/lamp oil/diesel for lamps. And charging batteries whenever a generator is running for power needs, like keeping the freezers cold.
Redundant systems so when a link in the chain fails (like the Xantrex inverter did) one is not "dead in the water" "up a creek without a paddle" whatever adage one prefers.
 
Supervstech, Absolutely! I will be quite happy if the unit handles 1000 watts on a sustained basis. The advert says 1500 sustained so I'm hoping for 1000. I was looking for a unit to power my home theater when the power goes out. At present I would fire up the generator and we would retire to the theater to spend the evening watching movies or even TV. And although the generator thru the transfer switch also powers the freezers, frigs, and septic pump (system that only runs short intervals four times a day at max) IMHO I think running the generator (5kw diesel) a huge waste of energy save for when one has power applications. Thus my quest for a simple solar setup to power the theater and perhaps a few light circuits. Since I live where solar is only viable (IMHO) for five or six months a year trying to create a "whole house" solar system makes little sense to me.
Generators for power applications; solar for lights and entertainment (when the season allows) and for long sustained outages during non solar times: kerosene/lamp oil/diesel for lamps. And charging batteries whenever a generator is running for power needs, like keeping the freezers cold.
Redundant systems so when a link in the chain fails (like the Xantrex inverter did) one is not "dead in the water" "up a creek without a paddle" whatever adage one prefers.
Where do you live?
 
I live on a small island (850 inhabitants) in the Pacific Northwest.
 
No ice flows... Olympic Peninsula, Washington State. Photos? This get offs topic real quick...I'm guessing you want photos of local geography...a quick search yields only one on this machine of the island...I have lots of animals: pileated wood peckers, coyotes, wood ducks, owls, hawks and of course bald eagles.... this photo was taken by a friend on his cell phone of a local cougar, but it shows the eastern coastline of the island.
IMG_0123.JPG
 
Plug a box fan or osculating fan into it. If it's a modified Sine Wave, it will usually hum and not be as strong (RPM's) compared to plugging it into utility power. Compare the difference.

The price seems too good to be true for a Pure Sine Wave Inverter. For a 3000 Watt Pure Sine Wave Inverter, prices average around $270 USD or more.
Agreed.
 
If you get the cheapest multimeter you can find (the chinese with yellow plastics), AC measurement works in a simplified way (I'm no electronic engineer, I'm not sure 'how' exactly) that takes a "slice" of the wave to "guess" what the voltage is. When the "wave" is actually a "stepped atrocity" like cheap UPSs usually do (when on battery mode), the multimeter won't read voltage correctly (usually way less: Like 140V instead of 230V)
 
Having just read through this post, no one has mentioned an important factor in regards to Pure Sine Inverters. There are TWO forms of Pure Sine Inversion in use today with significant differences which will affect how well they will work and their longevity given what they are being used for. There are Low Frequency Inverters which use big & heavy copper wound coils which not only makes the unites "very heavy" it provides them with a lot more tolerance and capability (4 normal 4kw inverter can peak to 3x capacity 12kw for surges). High Frequency units do NOT have the copper coils, instead they use cheaper MOSFETS and have a lower surge capacity, usually only double and often cost quite a bit less than High Frequency units. These are often referred to as "Car Inverters" in some circles.

REF: Inversion Methods Explained: High Frequency vs Low Frequency

Using MOD Sine or Square Sine is NOT good for fine electronics and most electronic motors. IF you get any "buzzing" from your electronics or appliances like your fridge motor, you are causing wear & tear & damage. Some inverters will actually create pulses which are visible to the eye... very bad for all equipment !
 
Those little pocket scopes are cute and I would almost be tempted to buy one. The reality is they are not that useful. For a few dollars more you can get a two channel USB scope to use on your laptop That has a lot more features and will likely not grow out of. Nice to be able to grab a screen image and post it.
 
Steve_S.... I am low on the learning curve with all this but from what little I have picked up I agree completely.

efficientPV....What I was looking for was something that I could put in my pocket/glovebox of car and readily have available so when a unit was presented as sine wave I could at least check to see if it really was what it claimed to be. My total investment in this unit is US$33 which is about the same cost as taking a friend for lunch where I live. This is my first oscilloscope and figured I'll probably damage it learning.

So the little unit arrived today. And like I said I am low on the learning curve. I have never touched an oscilloscope before today. After some puzzling the directions I managed to get everything hooked up and attempted a few readings.

First I tried a given source: the wall outlet. It registered it at slightly less than less than the expected 60 cycle...59. It has stop/run so I could get photos easily. The sine wave is not perfect. see photo 1

Next the 65 dollar "pig in a poke" sine wave inverter. It surprised me in that the sine wave was correctly formed. The cyclic rate was spot on 60 cycle.
see photo 2

Next I tried a cheapo 400 watt car inverter a friend gave me. As expected it was modified sine wave but had a cyclic rate of 153 hertz?! see picture 3

And finally I tried a UPS which had been the standby unit in my home theater for years to power down my DLP should/when the power would go out. It became redundant when I switched up to a larger LCD screen. It too was modified sine wave and said it was 114 hertz.

So if you look at the voltage readings they are way way off. I checked with a pocket meter (SperryDM-210A) which I more or less trust. The voltage for the wall outlet was 119 volts; the Pig was 114 volts; the Cheapo 400 watt measured 95 volts(?!) and finally the OPTI/UPS measured 100 volts. I don't know if one can calibrate the volt meter on this unit. Right now I sort of trust the presented wave form and the cyclic rate, perhaps it will do more as I learn to run the unit. I have included a couple of photos of the lash up I put together to make the measurements. I used my shooting bench with Wall Outlet.jpgPig in a Poke.jpgCheapo 400 Watt.jpgOPTI-UPS.jpg'Lash up' for testing units.jpg400 Watt 'lash up'.jpgbattery beneath with a Perko switch to separate the battery from the inverter when setting up.

Thoughts? suggestions on adjusting the voltage meter, greatly appreciated,
Wiley
 
It's actually not all that unusual to see your mains power has crest distortion as switchmode power supplies without power factor correction will take a bite out of the leading edge of the crest, and pretty much every house is full of devices with SMPSes these days.

Your 'scope is measuring peak to peak voltage and the 450v figure for the Opti UPS would be due to those downward heading transients. If you take the voltage from image 1, 345V, halve it to get peak voltage instead of peak to peak, and then multiply it by .707 you get the RMS voltage that you are familiar with. You could jiggle the equation so it becomes 345 * 0.3535, about 122v.

If you dig around in the settings it probably can give you a peak value instead of peak to peak, and you never know, it may even be able to show you RMS too.

The RMS value of the modified sine wave units can be calculated but you have to apply duty cycle measurements etc and it gets a bit messy.
 
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@Wiley Good stuff. Here's a test you likely hadn't considered, just for fun.... Run the power sources you have there with 2 or 3 different types of digital clocks and run them for a period of time 6-12 hours and see how accurate they are. ;-) I think some know what I am talking about.... If someone has medical needs or there is time sensitive (requiring accuracy) not all inverters are up to the task. A wee detail that can be a huge problem in some instances.
 
Steve_S.... I am low on the learning curve with all this but from what little I have picked up I agree completely.

efficientPV....What I was looking for was something that I could put in my pocket/glovebox of car and readily have available so when a unit was presented as sine wave I could at least check to see if it really was what it claimed to be. My total investment in this unit is US$33 which is about the same cost as taking a friend for lunch where I live. This is my first oscilloscope and figured I'll probably damage it learning.

So the little unit arrived today. And like I said I am low on the learning curve. I have never touched an oscilloscope before today. After some puzzling the directions I managed to get everything hooked up and attempted a few readings.

First I tried a given source: the wall outlet. It registered it at slightly less than less than the expected 60 cycle...59. It has stop/run so I could get photos easily. The sine wave is not perfect. see photo 1

Next the 65 dollar "pig in a poke" sine wave inverter. It surprised me in that the sine wave was correctly formed. The cyclic rate was spot on 60 cycle.
see photo 2

Next I tried a cheapo 400 watt car inverter a friend gave me. As expected it was modified sine wave but had a cyclic rate of 153 hertz?! see picture 3

And finally I tried a UPS which had been the standby unit in my home theater for years to power down my DLP should/when the power would go out. It became redundant when I switched up to a larger LCD screen. It too was modified sine wave and said it was 114 hertz.

So if you look at the voltage readings they are way way off. I checked with a pocket meter (SperryDM-210A) which I more or less trust. The voltage for the wall outlet was 119 volts; the Pig was 114 volts; the Cheapo 400 watt measured 95 volts(?!) and finally the OPTI/UPS measured 100 volts. I don't know if one can calibrate the volt meter on this unit. Right now I sort of trust the presented wave form and the cyclic rate, perhaps it will do more as I learn to run the unit. I have included a couple of photos of the lash up I put together to make the measurements. I used my shooting bench with View attachment 1729View attachment 1730View attachment 1731View attachment 1732View attachment 1733View attachment 1734battery beneath with a Perko switch to separate the battery from the inverter when setting up.

Thoughts? suggestions on adjusting the voltage meter, greatly appreciated,
Wiley

Steve_S.... I am low on the learning curve with all this but from what little I have picked up I agree completely.

efficientPV....What I was looking for was something that I could put in my pocket/glovebox of car and readily have available so when a unit was presented as sine wave I could at least check to see if it really was what it claimed to be. My total investment in this unit is US$33 which is about the same cost as taking a friend for lunch where I live. This is my first oscilloscope and figured I'll probably damage it learning.

So the little unit arrived today. And like I said I am low on the learning curve. I have never touched an oscilloscope before today. After some puzzling the directions I managed to get everything hooked up and attempted a few readings.

First I tried a given source: the wall outlet. It registered it at slightly less than less than the expected 60 cycle...59. It has stop/run so I could get photos easily. The sine wave is not perfect. see photo 1

Next the 65 dollar "pig in a poke" sine wave inverter. It surprised me in that the sine wave was correctly formed. The cyclic rate was spot on 60 cycle.
see photo 2

Next I tried a cheapo 400 watt car inverter a friend gave me. As expected it was modified sine wave but had a cyclic rate of 153 hertz?! see picture 3

And finally I tried a UPS which had been the standby unit in my home theater for years to power down my DLP should/when the power would go out. It became redundant when I switched up to a larger LCD screen. It too was modified sine wave and said it was 114 hertz.

So if you look at the voltage readings they are way way off. I checked with a pocket meter (SperryDM-210A) which I more or less trust. The voltage for the wall outlet was 119 volts; the Pig was 114 volts; the Cheapo 400 watt measured 95 volts(?!) and finally the OPTI/UPS measured 100 volts. I don't know if one can calibrate the volt meter on this unit. Right now I sort of trust the presented wave form and the cyclic rate, perhaps it will do more as I learn to run the unit. I have included a couple of photos of the lash up I put together to make the measurements. I used my shooting bench with View attachment 1729View attachment 1730View attachment 1731View attachment 1732View attachment 1733View attachment 1734battery beneath with a Perko switch to separate the battery from the inverter when setting up.

Thoughts? suggestions on adjusting the voltage meter, greatly appreciated,
Wiley
 
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