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The Handheld Oscilloscope is
an Essential Piece of Test Equipment
For Electronics and Microcontroller Work

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.



Note: You don't need to break the bank to get one and they will pay off for years to come.

In microcontroller work you will often want to find a glitch or record a waveform so you can see exactly what sequence of event occurred and the Digital Scope is Ideal for that.

For example debugging serial protocols such as RS232 and I2C is much easier with a digital scope - if you don't have one you'll have to use the simulator in the software to check it's operation and that can be unreliable as in the 'real world' things often don't work as you expect e.g. capacitive loading, inputs drawing too much current etc.

Note: Without a scope much of electronics is a wing and a prayer - I don't care what you say, even you have got the worst, oldest, lowest bandwidth scope it is STILL infinitely easier than guessing what's going on.

I'll just talk a bit about the three different types of oscilloscope you can buy these are the

  • Analogue
  • Handheld
  • PC based

But first some IMPORTANT points
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.

It is the BandWidth (or sample rate) divided by 10
that is THE REAL CAPABILITY of the scope


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.

Analogue Oscillosope

stb16 analogue oscilloscope

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


Digital HandHeld Oscilloscope

hand held digital oscilloscope

This handheld oscilloscope has the following features:

  • Sample rate : 10MHz (You'll really only get a good view of 1MHz)
  • Analogue BW : 2MHz
  • Timebase up to 1 hour per division.
  • It's a DVM.
  • Has easy frequency readout using markers.
  • Has memory recorder function i.e. it is a DSO.
  • Has a memory signal compare function.

So as well as being a full oscilloscope it is a recorder and DVM all in one .

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:

  • 10MHz sampling rate
  • 0.1mV sensitivity
  • up to 2MHz analogue bandwidth
  • 5mV to 20V/div in 12 steps
  • 200ns to 1hour/div time base in 32 steps
  • full auto set up
  • trigger mode: run, normal, once, roll, slope +/-
  • X and Y position signal shift
  • DVM readout with x10 option
  • audio power calculation (rms and peak)
  • dBm, dBV, DC, rms ... measurements
  • signal markers for Volt and Time
  • frequency readout (through markers)
  • recorder function (roll mode)
  • signal storage (2 memories)
  • LCD: 128x64 pixels / high-contrast
  • up to 20h on alkaline batteries
  • power supply: 5 x 1.5V AA battery or Nicd / NiMH (not incl.)
  • includes battery charging circuit 

Click here to order



The last on is the PC Based Oscilloscope

PC Based Oscilloscope
This one connects through the parallel port and has the following specs:
12MHz 3db point and it's definately not as portable as the handheld oscilloscope.

Disadvantages:

  • Parallel port - check you've got one!
  • Not portable.
  • Slightly worse input sensitivity (10mV) than the handheld 
    which has 0.1mV 
  • Uses the PC - you probably want to use it for something else!

Advantages:

  • Record all data to the PC for full analysis.
  • Does spectrum analysis - very useful for opamp db plots.
  • Auto setup - push a button and it will look for a signal.
  • Record and display all screen data - useful for reports.

At the time of writing it costs $189.95

Click Here to order

The full spec is:

Features:

  • Includes 110VAC Power Adapter
  • 1 channel
  • Input Impedance: 1Mohm / 30pF
  • Frequency Response: 0Hz to 12MHz (± 3dB)
  • Step Markers for Voltage, Time and Frequency
  • Vertical Resolution: 8 bit
  • Auto setup function
  • Optically isolated from computer
  • Record and display of screens & data
  • Supply voltage: 9 - 10V DC / 500mA
  • Dimensions: 9" x 6.5" x 1.8"
  • Weight: 14oz

Minimum System Requirements:

  • IBM compatible PC
  • Windows 95, 98, ME, (Win2000 or NT possible)
  • SVGA display card (min. 800x600)
  • Mouse
  • Free printer port LPT1, LPT2 or LPT3
  • CD Rom drive

Oscilloscope Specifications:

  • Ttimebase: 0.1µs to 100ms per division
  • Trigger source: CH1 or free run
  • Trigger level: adjustable per ½ division
  • Input sensitivity: 10mV to 3V per division
  • Record length: 4096 samples
  • Sampling frequency: 800Hz to 32MHz (Real time)
  • True RMS readout (only AC component)

Transient Recorder Specifications: 

  • Timescale: 20ms/div to 2000s/div
  • Max record time: 9.4hour/screen
  • Automatic storage of data
  • Automatic recording for more than 1 year
  • Markers for time and amplitude
  • Zoom function

Spectrum Analyzer Specifications: 

  • Frequency range: 0 .. 400Hz to 16MHz
  • Linear or logarithmic timescale
  • Zoom function 

PC based oscilloscope

PC Based Oscilloscope

PC Based OscilloscopeClick here to order

Conclusions:

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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