I need to get a digital scope. Since I will want to use it in the field some, I'm thinking along the lines of a computer plugin type. Typical use will be for audio range stuff and microcontroller signals.
Any thoughts or suggestions as to things to look for and/or specific products to consider or avoid?
Thanks, Scott Kelley
Figure you'll want to see at least the fifth harmonic (unless square waves that are indistinguishable from sine waves are OK), so take the single shot (not repetitive) sample rate (say 40 Msps for a popular model) and divide the Nyquist freq by five: 4 MHz. That's certainly OK for audio and quite a bit more. Just know what it is you're getting.
Digital displays are fairly cheap and easy (as compared to the monster CRTs and supporting electronics of a generation ago) so consider that on a real portable scope you're paying for the sampling and the signal processing, not so much the user interface -- and you'd pay just about as much for an equivalent capability if the GUI was offloaded to a PC.
If you need to be "battery portable" the price goes up a bit but if you can get along with a power cord, Tek and HP both have very capable digital scopes in the $1200 - $2K range that are small enough to take along with you. If you really need battery portable, add Fluke's ScopeMeters to the mix along with the other two.
-- Rich Webb Norfolk, VA
I have been using a Fluke Scopemeter 97 for about 8yrs. They are excellent but expensive. I think the newer models are even better. The one I have has a link for the PC but I think it costs me extra.
There are some very nice devices like this on the market, however, the speed of most of these limits their use to audio work for the most part. I really wouldn't want to use any that I had access to for digital work. Most of these are produced by small garage firms, and usually advertise for sales in publications like 'Nuts & Volts'. These of of limited use, but in certain situation they are 'the handiman's friend', just like Duct Tape.
A common feature on many of these is the ability to display in either the time domain or the frequency domain (Fourier Transform). This is a surprisingly useful feature in audio and analog communications work, particularly when working in the field and you have to carry and entire lab in your suitcase! :-)
Sadly I don't own one, so when I travel to the field to do work for the FAA or some other organization, the only off-the-shelf instrumentation I carry with me is a Tek pocket oscilloscope (owned by my employer), a laptop and prom burner (for implementing embedded code changes in the field), an inexpensive Wavetek DMM, a small set of handtools, a small soldering iron, and a few home made kludges that often prove useful in my field of work.
You'd be amazed at how useful a simple 9-volt battery with clip on test leads soldered to it can be for tracing and polarizing comm lines, forcing logic states (with a current limiting resistor) and a myriad of other uses.
Kindest regards, Harry C.
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