The handheld Oscilloscope (or other type) is the best investment you will
ever make and a portable handheld type is the most useful.
As well as the normal ability to measure voltage and frequency the digital scopes allow you to easily record transient or long term signals and some allow fourier spectrum analysis.
Digital HandHeld Oscilloscope
But first some
on Signals, Probes and Bandwidth
POINT1: Any scope (even a handheld oscilloscope) that you buy whether it is a high end on or a low end one if it says it has a bandwidth of X (or a sample rate of X) then you will only get to view a reasonable waveform AT A MAXIMUM OF X/10.
So if you have a 500MHz capable scope you are only going to easily see 50MHz signals maximum. Similarly 10MHz ones only show 1MHz signals properly and it's the same for the sample rate i.e. treat the sample rate the same way.
Note: there is one cheat and that is for the analogue scope where there is a x10 button (essentially this speeds up the signal that controls how the cathode beam crosses the screen i.e. it moves it faster so you can see more waveform - the disadvantage is that the scope is uncalibrated i.e. the signal is not guaranteed accurate. It's sometimes useful.
POINT2: Analogue input bandwidth - THIS IS DIFFERENT TO THE INTERNAL BANDWIDTH capability OK. The analogue input limits the input signal separately from the internal bandwith or sampling rate.
So if you use a scope with a small input bandwidth don't expect to see a signal above that bandwidth (OK it's a capacitive filter so you will see a reduced signal at 3db/octave lower - essential you won't get a real signal) because it is filtered.
REMEMBER: The sample rate and scope bandwidth are used to SELL YOU ON HOW GOOD THE SCOPE IS - but it means SQUAT.
One other point: Remember fourier transforms where all signals are made up of combinations of pure sine waves well the input bandwith (and internal bandwidth/sample rate) act as high frequency filters. So you loose high frequencies - that means if you look at square waves THE EDGES BECOME ROUNDED as the high frequency information is lost.
Just remember what you see is never what is really going on and it depends on the scope specs, the probe specs AND how you connect the probe to the signal.
POINT3: OK one more point - you know that great big loop of wire when you connect the probe to the signal and the probe's ground ten miles away (because the ground pin is over there on the other side of the board) - well you are creating a magnetic induction loop (remember the metal detector?).
Essentially any electrical activity inside/through that loop induces another signal (noise) into the circuit (into the scope input). So keep the ground loop small - the best way is to connect to a ground as close as possible to the signal. Professional probe kits have little springy wires that wrap around the end of the probe (Ground area) letting you create the smallest loop possible i.e. receive the best signal capture.
Right I've run out of points so lets talk about scopes (at last).
Lets start with the analogue scope.
I have put this scope up to show you the most basic scope you can buy and I would not recommend you buy this for any serious work. It's very bluky and far more difficult to use than a handheld oscilloscope. The best feature is that it has two input channels.
Lets look at the relevant specifications (you can see all of them by clicking the image above):
Bandwidth : (-3dB): DC: 0～10MHz, AC: 10Hz~10MHz
So that's really 1MHz signal view
Sweep rate : sweep rate: 0.1μs/div～0.1s/div ±5%
So that 1/0.1e-6 allows a 10MHz maximum frequency
At the time of writing this it costs $149.95
So as well as being a full oscilloscope it is a recorder and DVM all in
At the time of writing this handheld oscilloscope costs $169.95
Click here to order the handheld oscilloscope
Here's the handheld oscilloscope full spec:
Minimum System Requirements:
Transient Recorder Specifications:
Spectrum Analyzer Specifications:
I would recommend the handheld
oscilloscope for general lab bench work and the PC
Based oscilloscope for more in-depth analysis of individual signals.
Remember each of the above scopes is great value because they are about the same cost as a good multimeter.
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