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29

You should never float a scope with an isolation transformer! This is reckless and dangerous advice from your professor, and he/she needs a reality check. The accepted procedure for doing work that requires isolation is to ISOLATE THE UNIT UNDER TEST, NOT THE TEST EQUIPMENT. Why? It's much easier to remember that the unit under test is what's unsafe and ...


25

I'd firstly agree with other posters as to economics of scale. Consumer devices are produced in the millions whereas such a market does not exist for digital oscilloscopes. Secondly, oscilloscopes are precision devices. They need to undergo rigorous quality control to ensure they live up to expected standards. This further increases costs. As for ...


23

The DSO Nano is a poor choice for a hobbyist's oscilloscope. Capabilities It's really only good for audio bandwidth signals - anything above 100kHz is going to be visible, but unmeasurable. By most standards you want the sampling rate to be 10x the bandwidth of the signal in order to get close to measuring significant parameters of the signal (peaks, rise ...


23

Yes, that's normal. Due to its high impedance the probe acts as an antenna for the 50Hz field from the mains which fills the space surrounding the wiring (i.e. any room in your house). You'll notice that touching the probe will even show a stronger signal, indicating that your body is even a better antenna.


21

System bandwidth is a combination of probe bandwidth and oscilloscope input bandwidth. Each can be approximated by an RC lowpass circuit, which means delays add geometrically: t_system^2 = (t_probe^2 + t_scope^2) f_system = 1/sqrt((1/f_probe)^2 + (1/f_scope)^2) This means that a 10MHz 'scope with 60MHz probes can measure sinusoids of frequency 9.86MHz ...


20

The first thing I would do is read some literature on how scopes work. Tektronix has a good white paper called XYZs of Oscilloscopes. Next, you should hook up a function generator and figure out how the different display controls work. This includes the Y scale [Volts] and the X scale [Time]. Once you feel comfortable with those get comfortable using ...


19

Oscilloscope probes aren't just pieces of wire with pointy end attached to them. Typical probe will in addition to the pointy stick and the alligator clip have the input attenuation circuitry and impedance matching circuitry inside. Basically the oscilloscope input front-end has its own internal capacitance and its own internal resistance. In order to ...


18

At it's heart, a (digital) oscilloscope is just an ADC, along with some memory to hold the samples. The samples are then read out of the memory and displayed. The practical implementation issues make commercial oscilloscopes complicated. The input signal needs to be scaled appropriately for the range of the ADC, which means that you need to have attenuators ...


16

The ground clip on your o-scope is actually tied to ground. it is a hard short and rather low resistance. This means that you are shorting the 3.3 rail to ground with your ground probe. To fix this there are two options, Put the resistor in the return path so that one side of it is ground. That way the ground probe does not hurt it. Use two probes, one ...


16

You don't mention exactly what work you do, but a good DSO will last you a while (and I guarantee it won't go out of date for a while). Sure, you can grab a Tek analog scope 2nd hand but my storage scope has saved my frustration bacon more than once. I have a Rigol DS1052E (a good review from a proper EE here) which is a 50mhz 1GSa/s scope direct from the ...


16

This comes down to a question of bandwidth and latency. For a simple system let's assume one probe with 100 MHz bandwidth with 1GS/s sampling rate and an 10-bit A/D converter (I've had bad experiences with 8-bit scopes). I want a real-time display on the PC with a minimum sampling window of let's say 10ns - 1 cycle of a 100MHz sine wave and a maximum ...


15

Lower production volumes are a major cause and secondly, you're buying test equipment which is something special. If you only look at the teardown of a cheap DSO like a Rigol DS1052 you will see what's required just to make a low-entry scope. They have 5 dual ADC's (overclocked, so that already reduces pricing!). If those ADC's were $4 each (a random guess, ...


15

There are a few reasons for this: Nyquist's theorem applies to reconstruction of sinusoidal signals of infinite duration from jitter-free, perfectly accurate samples. Real measurement device clocks have jitter and fixed frequencies, real samples have measurement error and real signals are not infinite sinusoids. Jitter is the difference between a ...


15

It's a "Probe tip ground clip" (or something very similar like the examples below) An example of it being named as such is here. It's called "Probe tip ground" here. It is also called a "Probe tip spring adapter" here. Whatever it's exact name, I think the main thing is to have "tip" in there, as it differentiates from the standard ground clip by implying ...


15

The alligator clip on the scope probe: (image source) is connected, through the power cord, to Earth. If you clip it to something that isn't at Earth potential, you get a large current, and things go boom. That said, an isolation transformer on the scope isn't the way to go. There's a reason the engineers built the scope like this, and it has to do with ...


14

I'm not sure what the distinction is between the two choices in your question, but the real answer is that the gain of the amplifier(s) inside the scope is "flat" up to that frequency. In other words, the voltage measurements you make on the screen will be "accurate" up to that frequency. Above that frequency, the values will appear smaller than they ...


12

IMHO for its low price, the DSO Nano is actually a good first-time scope. As others have mentioned, you will have problems with showing anything faster than 100-250KHz coherently, but this is pretty high for quite a lot of uses. Yes, you won't be able to see system clocks or PWMs with it, but in my experience a scope is more useful for analog signals, and as ...


12

Two issues come to mind: Is the ground clip of your probe connected such that you get the shortest possible connection to the return of your signal source? (If the logic IC or FPGA has supply pins buffered with capacitors, connect your probe's ground clip directly to the ground node at these capacitors.) Is your probe compensated? It's not enough to use a ...


12

It is what it looks like - a ground spring*. At least that's what Agilent call it.


11

Your typical hobbyist microcontroller can range anywhere from KHz up to 40MHz or more. So if you are wanting to have a microcontroller running at lets say 40MHz and be able to see what a PWM looks like, you may be out of luck. However, if you are just wanting to see a general idea of what is happening on your analog circuits or simple digital circuits then ...


11

If you're designing your own boards, add test points. Aside from that, soldering on short bits of wire is the best solution I've found so far. I find that the amount of time it takes to strip and solder a wire is far less than what I'd otherwise waste futzing with clips or trying to hold a probe just so while also keeping an eye on a scope.


11

It appears that you are not an electrician, so this requires a bit of a boilerplate: Working with mains power should be performed according to your region's laws. It is dangerous and can seriously injure and kill you. Even the Earth wire is not at 0V with respect to the objects around you, due to unequal split-phase loading (or other more scary ...


11

The ground clips on your probes are connected to Earth ground by means of the oscilloscope power plug, in a roundabout fashion. This means you can't connect it anywhere but Earth ground (green wire in North America), and even then the path between your circuit and your oscilloscope plug may be so long that there is a voltage differential and capacitance, ...


10

The times when I have needed a four channel scope, are few, but when I do there is no replacement for it. You mentioned serial protocols, using four channels can really help debug SPI communications, especially if the scope is fitted with a analyser to convert the SPI waveform into actual characters! Having said that, buying a two channel scope, and then ...


10

First you have to set persistence on your scope. Normal persistence will show newer data over the previous, while older data fades at each scan. Infinite persistence also displays new data over the older, but the older doesn't fade, so that you can have literally thousands of images on top of each other. There are two ways to create eye diagrams. One uses ...


10

Price points always vary - especially with used scopes. You're likely to find a lot of old Tektronix two-channel analog scopes. If you're lucky they will include probes. Bandwidth - You should look for 50-100MHz. Bandwidth tends to increase in multiples of 100 after that point, then multiples of 1GHz after the 1GHz mark. You might find a 150MHz or ...


10

WARNING: Means of being less likely to die or to kill others is discussed below. Reading may be considered useful.. Consider this "informed opinion" rather than holy writ. In an oscilloscope you want the best result you can get for the money and it's far easier to build a single ended amplifier rather than a differential one when you want ruler flat gain ...


10

Oscilloscopes usually require significant power and are physically big. Having a chassis that size, which would include exposed ground on the BNC connectors and the probe ground clips, floating would be dangerous. If you have to look at waveforms in wall-powered equipment, it is generally much better to put the isolation transformer on that equipment ...


10

You didn't give us the important information about what speed the SPI signals are or what exactly you expect, but it looks like you are sampling the signal way too slowly. That plots seems to be at about 20 µs per division, which is a very long time for lots of SPI busses. SPI could be operating at 10 MHz or more. Crank up the time resolution and ...


9

Yes, the Owon should do okay for all the mentioned computers. 20MHz bandwidth is a perfectly good choice for your first scope, and will cover most of the "less complex" and older digital electronic components, for example small microcontrollers (e.g. PIC10, 12, 16, and 18F and similar Atmel, TI, etc offerings) The highest clock speed out of the computers ...



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