Thanks all for the great info! It helps to have these perspective after = all I've read about scopes. My multimeter has a Hz setting. I used it to tune a 555 chip to 40kHz. = Is this what you mean by a counter? What do I want to do? Not sure. I've been a programmer on mainframes = my whole life, and at the beginning of this year my wife got me a little = robot kit, from there I went to PIC's, and now I'm trying to learn = electronics, something I've tried to understand since I was a kid. (Is = it a different way of thinking, electronics and programming?) So the truth is that I was programming Pic assembler in a couple of = days, but it took me about a month to figure out what a pull-up resistor = was, for example. (-: =20 I'm just getting the basics of electronics and I thought that at times a = visual representation of what I was working with might help me in my = understanding of how things work, so that then I can build my own = circuits. This is why I was curious about scopes. Thanks very much. Lindy -----Original Message----- From: pic microcontroller discussion list = [mailto:PICLIST@MITVMA.MIT.EDU] On Behalf Of John J. McDonough Sent: Wednesday, June 02, 2004 17:25 To: PICLIST@MITVMA.MIT.EDU Subject: Re: [EE: ] what is a logic analyzer? ----- Original Message ----- From: "Lindy Mayfield" Subject: Re: [EE: ] what is a logic analyzer? > What would be the next logical piece of test equipment (after > a nice multi-meter) for a still-learning electronics hobbyist? > Would it be an oscilloscope? Depends a lot on what you do. For some folks, a counter is the next = toy. With a PIC, it's pretty cheap and easy to make a reasonable counter. = But an oscilliscope is tough to live without. > I've seen both scopes and logic analyzers that interface with > the PC -- they seem to be cheaper cause the PC does all the visual > -- and I wasn't sure the differences. A problem with PC scopes is usually the bandwidth. Unfortunately, this = is also the problem with cheap scopes. The bandwidth of a scope tells you the maximum frequency for which it = will faithfully reproduce a sine wave. However, you are rarely interestd in = sine waves, unless you are mostly doing audio. Scopes fall off gradually = above the spec frequency, so if you look at, say, a 50 MHz signal with a 20 = MHz scope, you will see something. That something won't be the same shape = and amplitude as the original, but it will be something. If you remember our old freind Fourier, you will recall that any = periodic waveform can be looked at as the sum of a series of sine waves at = integral multiples of the basic period. If you looked at a 20 MHz square wave = with a scope that had a hard limit above 20 MHz, you would see a 20 MHz sine = wave. Now real scopes don't have a brick wall, they fall off gradually, so you would see a square-ish sine wave on a 20 MHz scope. What this all means is that you would like a scope at least 3x the = maximum frequency of interest. For most hobbyists, this means 100 MHz or so. If you can afford a large instrument, used 100-200 MHz scopes can be had fairly reasonably. Physically smaller scopes tend to cost a lot more. Tektronix scopes like the 465/475 are very popular for hobbyists on a budget. These are very nice, but they are quite large. One good way to get the lay of the land is to poke around on eBay. Look = at the "completed auctions" to get an idea of what is available at what = price. Typically, these things shoot up at the last minute, so auctions that haven't completed yet don't give you much of an idea. I'm always a little squeamish about buying stuff on eBay, although I = have never had a bad experience. I've bought quite a few scope probes there, among other things. Another thing eBay is good for ... many of the = scopes sold there are by dealers. You may find a dealer near you. 72/73 de WB8RCR http://www.qsl.net/wb8rcr didileydadidah QRP-L #1446 Code Warriors #35 -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details. --- Incoming mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.663 / Virus Database: 426 - Release Date: 4/20/2004 =20 --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.663 / Virus Database: 426 - Release Date: 4/20/2004 =20 -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.