I need to buy one. I’m not experienced enough to figure this out without seeing actual output data. I think amazon has the same one your talking about. I was nervous to order it though.

DSO 138 Oscilloscope Kit Open Source with Probe 2.4" TFT 1Msps Digital Oscilloscope Kit with DSO 138 Case + Probe 13803K for Electronic Learning Set https://www.amazon.com/dp/B07SL8KQPZ/ref=cm_sw_r_cp_api_i_1rAkFb41D7EY4 is this it?

 

DSO 138 Oscilloscope Kit Open Source with Probe 2.4" TFT 1Msps Digital Oscilloscope Kit with DSO 138 Case + Probe 13803K for Electronic Learning Set https://www.amazon.com/dp/B07SL8KQPZ/ref=cm_sw_r_cp_api_i_1rAkFb41D7EY4 is this it?

I bought this one from Ali Express.

https://www.aliexpress.com/item/32778225027.html?spm=a2g0s.9042311.0.0.5c854c4dS3mydL

These all seem to be clones of a Chinese product. Sad, but that's reality. I was buying some BTY 9V NiMH batteries. Bought some more, and they were knock offs. They even copy mispelled words.

 

I bought this one from Ali Express.

https://www.aliexpress.com/item/32778225027.html?spm=a2g0s.9042311.0.0.5c854c4dS3mydL

These all seem to be clones of a Chinese product. Sad, but that's reality. I was buying some BTY 9V NiMH batteries. Bought some more, and they were knock offs. They even copy mispelled words.

What’s sad about it? I think often it is a pcb/soldering factory designing the circuit boards, another Chinese company purchases them and decides what will be screen printed on them and where they will fulfill the through holes, then they are sold to different countries. Just a guess though.

 

What’s sad about it?

In the US, we frown on companies stealing intellectual property from it's rightful owners. We have to take that position or anyone could steal our IP and we'd have no leg to stand on if we condoned that behavior in other countries.

It would be different if the cloners were authorized or were paying royalties to the original creators, but that isn't the case here.

 

In the US, we frown on companies stealing intellectual property from it's rightful owners. We have to take that position or anyone could steal our IP and we'd have no leg to stand on if we condoned that behavior in other countries.

It would be different if the cloners were authorized or were paying royalties to the original creators, but that isn't the case here.

I always assumed the cheap scopes originated in China. I understand what your saying now though. I didn’t want to assume you were from America, because I was about to share a strong opinion in favor of America and how much intellectual property is stolen from our country.
I guess I will have to buy that little scope then. I wish there was a way to measure my rectified transformer without one. I have a hot water heater element that I am using to try and measure the amperage under load. Do you have any ideas?

 

I didn’t want to assume you were from America, because I was about to share a strong opinion in favor of America and how much intellectual property is stolen from our country.

You shouldn't have to be an American to believe that stealing is wrong. If companies that create intellectual property can't recover their investment, they'll go under and stop innovating. It helps the World when creativity and investment return dividends that encourage more creativity and investment. Thieves are just out to make a buck at the expense of someone else. They're leaches on humanity.

I have a hot water heater element that I am using to try and measure the amperage under load. Do you have any ideas?

I'd use a clip on ammeter.

 

You shouldn't have to be an American to believe that stealing is wrong. If companies that create intellectual property can't recover their investment, they'll go under and stop innovating. It helps the World when creativity and investment return dividends that encourage more creativity and investment. Thieves are just out to make a buck at the expense of someone else. They're leaches on humanity.
I'd use a clip on ammeter.

This is true, it’s funny how much spying and stealing is incentivized these days. If the money is right you can get away with horrible crimes.
I said current, but I meant voltage. I believe you were the one that told me voltage has to be measured by the scope after rectification. I went ahead and ordered the amazon version of the one you bought. It will be here tomorrow.

 

I went ahead and ordered the amazon version

Note that the maximum input voltage is 50V. If you're going to measure higher voltages, you should use a 10X scope probe or a voltage divider. If you use a voltage divider, be mindful of the resistor maximum working voltage.

 

Note that the maximum input voltage is 50V. If you're going to measure higher voltages, you should use a 10X scope probe or a voltage divider. If you use a voltage divider, be mindful of the resistor maximum working voltage.

Thanks for the heads up. How does one use a shunt to measure accurately. How do you know how much material should be used for a specific voltage drop?

 

Thanks for the heads up. How does one use a shunt to measure accurately. How do you know how much material should be used for a specific voltage drop?

I have seen guys buy shunts and remove material to get the drop they want, but how could they be sure it is accurate?

 

I have seen guys buy shunts and remove material to get the drop they want, but how could they be sure it is accurate?

Not sure what shunts you're referring to.

You can use a string of low wattage resistors to divide the voltage. Most 1/4W resistors have a working voltage of 200V. If you put 10 1k resistors in series and take the voltage from the last one, you'd have a 10:1 divider. You could use 9.09k and 1k, but you'd need to look up the working voltage for the resistors. By using 10, you don't really need to worry about it as long as you're not working with voltages higher than 220VAC.

I'd use a 10:1 scope probe. The one I checked was rated for 500V.

 

Not sure what shunts you're referring to.

You can use a string of low wattage resistors to divide the voltage. Most 1/4W resistors have a working voltage of 200V. If you put 10 1k resistors in series and take the voltage from the last one, you'd have a 10:1 divider. You could use 9.09k and 1k, but you'd need to look up the working voltage for the resistors. By using 10, you don't really need to worry about it as long as you're not working with voltages higher than 220VAC.

I'd use a 10:1 scope probe. The one I checked was rated for 500V.

It was something I have always wondered. When I got into electrochemistry my first power supply was a computer power supply and I was instructed to buy old mechanical voltage and amperage gauges on eBay and to buy a thick metal shunt to divide the voltage to get a millivolt per volt drop I believe. The part I ordered I never used cause I didn’t understand how it was supposed to work, but it is literally a thick piece of metal with a bolt on each end to attach + from a dc power supply. I never got an explanation from the person that was helping me and we aren't in touch anymore.

 

It was something I have always wondered. When I got into electrochemistry my first power supply was a computer power supply and I was instructed to buy old mechanical voltage and amperage gauges on eBay and to buy a thick metal shunt to divide the voltage to get a millivolt per volt drop I believe. The part I ordered I never used cause I didn’t understand how it was supposed to work, but it is literally a thick piece of metal with a bolt on each end to attach + from a dc power supply. I never got an explanation from the person that was helping me and we aren't in touch anymore.

Sorry, it was completely unrelated. Telling me the scope only went to 50 volts and how to divide the voltage reminded me of it

 

to buy a thick metal shunt to divide the voltage to get a millivolt per volt drop I believe.

That doesn't make sense. A metal shunt is just a resistor. The voltage it drops will be proportional to the current through it. That would only work if the current was fixed.

I never got an explanation from the person that was helping me and we aren't in touch anymore.

An analog meter movement has a full scale deflection current and a resistance. The way meter shunts work is they establish a current divider with the meter.

Say you had meter with a 1mA full scale deflection current and you wanted it to measure 1A. You would select a shunt resistance that was 1/999 times the resistance of the meter.
EDIT: corrected ratio.

 

That doesn't make sense. A metal shunt is just a resistor. The voltage it drops will be proportional to the current through it. That would only work if the current was fixed.
An analog meter movement has a full scale deflection current and a resistance. The way meter shunts work is they establish a current divider with the meter.

Say you had meter with a 1mA full scale deflection current and you wanted it to measure 1A. You would select a shunt resistance that was 1/999 times the resistance of the meter.
EDIT: corrected ratio.

Idk, he was very knowledgeable, Unfortunately I didn’t care about learning back then. I’m sure I have explained it wrong. I will send you a picture when I get off work. He used to buy those shunts and grind metal off of it until he got the correct ratio. When he told me how to do all of this I had it written down, but I lost all of that material.

 

He used to buy those shunts and grind metal off of it until he got the correct ratio.

That makes more sense. He was adjusting the resistance of the shunt to get the ratio he wanted.

 

That makes more sense. He was adjusting the resistance of the shunt to get the ratio he wanted.

Got my scope. I’m looking for the rms reading of my rectified output from the transformer I wound, or is the Vmax?

 

I’m looking for the rms reading of my rectified output from the transformer I wound, or is the Vmax?

It depends on your intent.

RMS only applies to a sine wave. It's used to calculate power.

If you're going to filter it, you use peak voltage because that determines the required working voltage for the capacitor. For a conservative design, you derate the capacitor voltage. Some use 50%, but I think that's overly conservative.

 

It depends on your intent.

RMS only applies to a sine wave. It's used to calculate power.

If you're going to filter it, you use peak voltage because that determines the required working voltage for the capacitor. For a conservative design, you derate the capacitor voltage. Some use 50%, but I think that's overly conservative.

I need 6-7 volts and over 3 amps for electrochemistry project. I have no idea how to use that scope.

 

I need 6-7 volts and over 3 amps for electrochemistry project.

What is the voltage regulation requirement? Is pulsating current okay?

I have no idea how to use that scope.

The scope showed you a lot of information that isn't useful, e.g. RMS, peak to peak, and average voltage, and cycle, PW, and duty. You can measure or calculate the important things.

Don't get lulled in to using bogus information presented to 3 decimal places.

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