I do not have an Oscilloscope, but I want to check if my 12V DC to 230V AC inverter does produce a sine or a square wave. Any way to verify that?
I know how a sine wave and a square wave sound, so converting this to audio might be a possibility? Maybe with a transformer? Just some input ideas.
I would try a soundcard. Connect a resistive load (eg. light bulb) to the inverter. Wrap a piece of wire around one of the cables leading to the bulb (DO NOT CONNECT DIRECTLY), connect to mic input and try recording. You should be able to see how (un)clean the power is.
One way is to find the difference between peak and average of the half-waves.
Use a diode full wave bridge to rectify the output of the inverter. Put a 1 MΩ resistor across the output of the full wave bridge. Measure that with a ordinary voltmeter.
Now add a 10 nF capacitor across the resistor. This cap should be rated for 1 kV or more. Such caps are readily available up to 10 nF or so. Measure again with the meter. If the voltage is basically the same as before, then the output is a square wave. For a sine wave it should go up substantially, like 30 to 40 percent.
With a high fps camera set to manual exposure, a big resistor (>~10k), and a couple of scrap LEDs (not white) back-to-back in parallel you should be able to measure the brightness -- does it change smoothly or in steps? But you are working with mains if you build something like that, even if it is isolated from ground.
How easy it is to read the brightness of a spot from a video is up to you (I've written Python to do this for a series of stills but never coded any video analysis).
Here is what I would do:
First make a simple 100:1voltage divider to drop your voltage to a few volts. Then make a 12 dB/octave high pass filter and 12dB/octave low pass filter, both with the 3 dB cutoff centered at 75 Hz. Apply the low voltage to each, and with an appropriate value load resister on each filter output, measure and compare the AC voltages coming out of the filters. A true sine wave input will show very little output voltage from the high pass filter, and the low pass filter will show very little attenuation of the voltage (compare input to output). A modified sine wave or square wave will show significant AC output from both filters, and the low pass will show some voltage attenuation.
but I want to check if my 12V DC to 230V AC inverter does produce a sine or a square wave. Any way to verify that?
Be aware that the answer is very likely "neither". Olin's answer will distinguish a plain squarewave from a sinewave but it won't distinguish a "modified sinewave" from a "true sinewave".
Your idea of using a transformer is a good one, it will reduce the voltage to a safe level and provide isolation.
You can then use a resistive divider to further reduce the voltage to a volt or so and limit the current, then feed that in to the line input of your sound card and record the waveform.
Given the limitations of your measuring equipment, might you short circuit the whole problem by finding the manufacturer's specs, manual or data sheet? It may tell you what the output waveform is.
Use a PC oscilloscope that uses your PC sound card to take samples of signals.
You'll have to divide down the 230V to a much smaller level, like 2V, and then you can monitor it on your PC.
Here's another approach: if you say you can "listen", then first make sure that you attenuate the signal properly, and isolate it (if applicable), then use a first order highpass for 50Hz (a differentiator might also work, but it might be too sensitive, depending on the inherent pole; highpass better). The two sounds, incoming and outcoming, should sound the same if it's a sine (or very similar, considering filtered high-frequency switching noise). Else, you'll hear garbage in, and garbage out.
There are (A/D) adapter cards and plug-ins (USB) that allows a computer to run an app that provides the functions of an oscilloscope. I'm sure there are cheaper ones available (depending on accuracy and features you need), and perhaps you can borrow one.
Since you want to notice the difference between a sine wave and a square wave (as opposed to a sine wave and a modified sine wave), you could use a camera and a lightbulb for this.
For this, you need to setup your camera and environment in such a way that you can make 2 pixtures from the same lightbulb, connected first to your normal power outlet, and then to the power outlet of the UPS
If your camera has a manual expose mode, you can use this, and the lightning output of the bulb connected to the normal household power should be significantly weaker.
If your camera has no manual expose mode (most phones), open the resulting pictures, and see if the lighting time is significantly different
This difference is lighting output is caused by the fact that lightbulbs use the average voltage, while the UPS with it's square wave is designed to match the peak to peak voltage of a normal outlet, as most advanced electronic devices use diodes to rectify the power
The simplest way is try use it with universal motor such as beef cuting machine or drill machine . If square wave the machine will not work .if pure sign wave the machine will work normally
