Equipment to investigate signals

[R_C]

I've done basic electronics and microcontrollers but I'd like a point in the right direction. What type of equipment should a newcomer consider to investigate the signals of existing electronics?

For example, my first project would be to try to decipher and understand the signals and pinouts on the vintage 20-year old autopilot on my boat. The autopilot consists of a central control box with connections for a heading compass, control head, and rudder position indicator. The rudder position unit's specs show a frequency of 3400Hz for center with +/- 20Hz for each degree of rudder angle. Can I verify that signal with an oscilloscope (never used one)? If so, what type? To save money, are the USB units that work with a PC a good option? Thanks.

 

[KeepItSimpleStupid]

This is the newest thing: A MSO Oscilloscope or Mixed Signal Oscilloscope. I'm not advocating it, but look at the pretty pictures: **broken link removed**

Some the MSO scopes analyze IR signals or I2C or SPI signals. The hard part is triggering on the I2C signals without at least a device to generate the trigger.

Analyzing may require you to store or download the recorded signals.

Analog scopes have no means to store, but MAY have the means to measure a periodic signal directly.
The next step was Storage oscilloscopes - Again no downloading usually.
Then there are Scopes that digitize and offer measurements such as cursurs, P-P voltage, frequency etc.
Now comes the MSO or Mixed Signal Scopes.

Bandwidth will cost you. A 1 MHz BW scope is going to cost a lot less than a 2 GHZ scope.
Very high frequency scopes use a 50 ohm input. That is NOT what you want. You want a 1 M input.

The range of inputs from say 50 mV/div to 500 uV/Div are all possible. Adding a x10, x100 or x500 probe increases the range.
In order to see the EDGE of a square wave properly at high frequency, the scope probes have to be compensated. A real scope includes a calibration signal and the prove itself has a variable capacitor that needs to be adjusted to square up the square wave.

USB might damage your computer. I would not operate one without a USB isolator.

Look around.

 

[MikeMl]

A USB digital scope and a Laptop makes a great portable data aquisition system, runs on batteries away from mains. Also good for slowly varying and intermittent signals, such as you will encounter in an autopilot. I have used mine to debug an aircraft autopilot while in flight...

 

[KeepItSimpleStupid]

Search youtube for some videos.

 

[R_C]

Thanks for the suggestions. I'll start reading up on oscilloscopes and their use.

 

[ghostman11]

there is a pretty good video on youtube called scopes for dopes thats got alot of info in it mainly for analogue scopes but much is relevant for any scope

 

[fernando_g]

How serious are you about electronics?

A scope will be the most useful piece of equipment that you own, and most likely the most expensive.

As other posters mentioned, basic USB-powered units can be had sometimes for as los as USD$100.

But eventually you will need the features and bandwidth of more expensive ones.

One thing I can tell you, based on painful experience: get at least a 2 channel scope; you'll outgrow a single channel rather quickly.