Test Equipment - The Oscilloscope Part 1 (E.J. Daigle)

hi my name is EJ Daigle I'm the director of robotics and manufacturer technology today I'm going to give you a little brief on some lab equipment we use in our electronics technology and our automated systems and robotics programs and that's the oscilloscope I have some topic learning objectives here that I want to cover today on the first is that we're going to dispute upon successful completion of this topic the trainees should be able to describe how to take measurements with the oscilloscope the trainees should also be able to calculate for electrical unknowns from a screen trace and the trainees should be able to demonstrate proper measurement techniques using the oscilloscope so we'll jump right into it here to start off when we start using the oscilloscope here in a few minutes what you're going to see is that every oscilloscope has a front panel like this and on the X plane here this really represents time on the x-axis here it's really the Cartesian coordinate system no different than then working with algebra or any mathematics so the x coordinate here represents time the y coordinate here is going to represent amplitude okay and you guys will see here in a second how we actually take a voltage measurement with respect to time and that's amplitude with respect to time and then these graticule x' represent different quantities depending on what position your various controls are in so in this case um you might call this first one here 1 2 3 & 4 graticule if we call this middle 0 okay and then each each little tick mark here would be 0.2 0.4 0.6 point 8 or 1/5 of our of our quantity there okay so let's go ahead and take a look at a trace here and again in a minute we'll we'll actually walk over to the oscilloscope here and we'll actually do it in real time but first I want to show you if you are looking at this trace on an oscilloscope on an oscilloscope right now we'd be able to take a measurement using this trace on the first thing we'd have to do is is note what our controls are what our control settings are so I'm going to write controls here and let's say that our volts per division knob was set at 5 five and our time per division knob was set at one millisecond and that's also the same as saying point zero zero one seconds that'd be the same thing let's say for right now our times ten probe we haven't even talked about that yet but let's say our times ten probe is off and let's say our coupling is set to DC so what that means is right now we're going to read a DC waveform using the oscilloscope screen and this would be the trace that would show up on my oscilloscope so all I need to do to actually take this measurement is count the number of divisions so in this case if I count up from my zero this being my zero and I count up one two three divisions I have um I can determine what this voltage is so I see that my thick solid line is tracing across that third division here okay next thing I notice is that my volts per division is set at five so I have five volts per division I have one two three divisions equals fifteen volts DC and how do we know it's DC voltage we know it's DC voltage because it's a flat line if this is an AC or alternating current we would actually see some sort of sine wave or some sort of alternation and we'll go over those one of those here in a minute so our voltages 15 volts DC we also know that that voltage is positive because the voltage in this case is above the zero mark this being the zero mark if that voltage was at three three divisions below the zero mark we would know it would be a negative fifteen volts DC so in this case it's a positive fifteen volts DC now when we talk about period and frequency these really are specific to AC voltages so in this particular case both of these are not applicable so we have no AC voltage we do not have any change over time there is no variation in this voltage whatsoever all right we erase these ones and we'll move on to the next one and again we have amplitude and we have time and these will be our control settings for this particular example are our volts per division is going to be set at 2 volts time for division is going to be set at 2 milliseconds and times 10 probe is going to be off our coupling is going to be set to AC we know that this is an alternating wave form we know this is an alternating wave form because it's going up and it's going down so we do have a full alternating cycle here so go ahead and do some calculations based upon this one our volts per division and when you look at voltage of an AC wave from the oscilloscopes one of the few meters that you can actually do this on digital multimeter will read a see in RMS units on analog meter we can read ac and RMS units the oscilloscope is actually going to be the only meter where we can actually read a true peak to peak waveform so that's kind of a unique aspect of the the oscilloscope the other thing is that the oscilloscope is really good for reading high frequency signals Fluke digital multimeter will do pretty well but as soon as you get over a couple thousand hertz or 2k hertz um it starts to not keep up and processes quickly our oscilloscopes in the lab are all rated up - some of them are 10 megahertz and some of them read 100 megahertz so we could read a very very quick signal or a high a high-speed signal so in this case the volts per division we're actually going to look at our peak to peak waveform that's what we're concerned with here when I know what our peak to peak waveform is so we pick a peak right there that's the lower peak that's as low as this voltage goes again this would be my zero volt level and then we'll pick an upper peak and that's as high as my voltage would go and I'm going to look at the difference between the two so if this is really a 1 2 3 down and 3 up I like to actually just count the full peak to peak though so if I call this 0 if I just pretend this is 0 this would be 1 division 2 divisions 3 4 5 I can see I have six full divisions on my trace here so I'm gonna take my six divisions and again it's no different than it was for DC I'm going to multiply that by my volts per division which is two volts and that's going to give me 12 volts peak-to-peak I noticed that my x 10 probe is off so I don't have to do any multiplication or anything but now I want to figure out my period okay what your period is your period is the length of time it takes for one complete cycle and a complete cycle is where the wave form is going to repeat itself and this is an excellent example of what we will want our trace to look like we want as close to one complete cycle as we can get to have the best possible resolution so I can see my wave form starts right here and my wave form is going to end right here and it would it would repeat another one if it kept going on in time but we can see this takes up one full screen for a time period this is going to be my period from where it starts to where it finishes and starts over again so in this case I have one I'll just kind of count these for you there's 1 2 3 4 5 6 and as you get used to these you can just kind of do it on the fly there's 10 full divisions ok so it's 10 divisions I'm going to multiply that by my time per division because period is really a measurement of time because we're looking at that x axis which is a measurement of time so I'm going to look at my time per division which is 2 milliseconds so 10 divisions times 2 milliseconds and my period is going to be 20 milliseconds pretty easy to deal with there and as you get into basic electricity the other thing you'll discover is that frequency and period also have a reciprocal relationship such that frequency is actually equal to 1 over the period so that's kind of a nice thing to know and what frequency is where period is the time it takes for one cycle frequency is the number of cycles we get every single second the number of these complete waveforms we're going to have in a second ok so we do is we do a reciprocal of 20 milliseconds tip that into my calculator and I find out that this is actually 50 Hertz frequency is always measured in Hertz okay so that's one example there let's go on to the next one here screen down a little bit and again we'll look at our controls and let me get my sheet there we go I'm in this particular example we'll use a volts for division of five volts and a time per division of five milliseconds we're going to turn the times ten probe on this time and I'm actually going to like to write yes there but I'm going to call it on I'm going to circle that in red here in a second and I'm going to put my coupling on AC now again we know it's an AC voltage because we have an alternation here I do want to kind of make a note here though my times 10 probe is on what that means is when we get into the lab here you'll see that the probe actually has a times 1 times 10 attenuator so we can actually bring this into the screen it's kind of like attenuating that signal byte by 1/10 so you're only looking at 1/10 of the signal at a given time so if you had a signal that was way too big to fit on the screen you turn the times 10 probe on it would shrink and fit onto the screen but we have to account for that if we don't account for that times 10 probe we're actually going to be off in our calculation by a factor of 10 so that's not going to be a good thing so again we'll go ahead and work through this our volts for division out now that times 10 probe only affects amplitude it only affects voltage it's not going to affect our period or frequency there are some scopes that will have magnify or a gain and those may affect the both the y-axis the amplitude and the time axis on the x axis so there are some scopes that will have magnifying gain along with the times 10 probe but every scope has the times 10 probe it's it's a function of the probe not necessarily a function of the scope so in this case we want to calculate voltage so we had five volts per division well first we got to figure out the divisions let's figure out division this one's a little bit trickier I can see I have one full division up from my zero and then I have a couple pieces Oh point two and point four so I could take one point four multiply it by two or you could even on the scope you could actually move this down a little bit and and just look at it from a particular line and coming up with the portions in this case I'll count up how many there are it's 1.4 divisions up which in this case because it's centered on the zero it's also one point four divisions down yep um so that's going to be a total of two point eight divisions times five volts two point eight times five gives me 14 volts peak-to-peak um however R times ten probe is on so we have to multiply that by ten that's going to give us a hundred and forty volts peak-to-peak so that's the one thing you have to take account into with the times ten probe is you'll have to multiply by ten because of the probe there okay on the period we'll take a look at that real quick two divisions can see it starts here ends here and I could do that anywhere on the trace two divisions times five milliseconds equals a 10 millisecond total okay that's my period and then my frequency is going to be one over the period which is one over ten milliseconds so I'll do ten milliseconds in my calculator and do a one over X I get 100 Hertz just like that and that's a good demonstration of what we're going to go over in lab here in a few minutes you

Channel: Dunwoody College

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Keywords: dunwoody college, elftmann student, success center, tutoring, technical video, lecture, technology, oscilloscope, test equipment

Id: dTPHSDoWKU0

Length: 13min 5sec (785 seconds)

Published: Wed Dec 22 2010