Doug,
1. Buying the DS1054Z for the class - great idea.
2. Suggesting your students use the scope to probe 115V from an outlet - terrible idea.
If you are teaching an electrical safety class then there is a lot of ground to cover, lethal voltages, arc flash, grounding, etc. and I don't think you have time to do all that. The best reason of all not to let them do that is that, if one of your students managed to kill themselves (a definite possibility IMHO), your ass would be in the fryer and you could lose everything - house, 401k, etc.
So now you're thinking that I'm a do-it-by-the-rules boring old git eh? Try this, if you want to probe high voltages with your scope, cut the ground pin off your mains lead; now the ground on your scope will be floating. You could then fasten the live side of the 115 V to the ground on your scope and there will be no explosion, no fried PCB, no smoke from the ventilation holes It works because the SMPS bricks are (almost always) isolated so there's no connection from input to output - you can prove this to yourself with an ohms meter.
I do this all the time but I have a note on the front of my scopes reminding me that they're not grounded.
I am a college professor who teaches computer networking, server administration, virtualization security and digital forensic investigations. . All of the classes I teach are advanced level classes.
This semester I was asked to teach a college level class to high school students. (I actually have an 8th grader.). These kids are smart and are eager to learn. The class is an introduction to computers class and is suppose to teach them how to solve “business” problems with computers.
I am taking the liberty since the course does not specifying what type of computer or programming language is to be taught in the class to use Arduino. Right now I have the studnets going through the standard labs. The business problem they are going to solve is to build a replica of an arcade game and learn how to hack it. (Actually the real arcade game is “rigged” so players who win only actually win 1 in 30 plays. The business problem I’m teaching them is games of skill may not.... They are rigged.
So why the scope? It’s a real stretch for what I’m teaching. But these kids are smart and I am teaching them networking and computer protocols. I’ve already taught them how to use a multimeter (HarborFreight) to measure DC voltages and currents to determine the DC voltage and current of one mini-Christmas light from a string of 100 which is spec’d at 120 VAC, We actually found the bulbs could be run at 220vac.
Since our college doen’t have the budget for every student to blow a channel in a scope I’m the only one that will be using it. I did watch Dave’s video on scope gnd fully understand what he’s talking about. The Arduino when connected with USB to a computer I’m sure are earth grounded. Something I’m always thinking about.
I want to use the scope to show students the scope show voltages a multimeter can’t display. And then I would like to show them how to use a scope to “see” a protocol and to my +1 the Rigol has a decoder for the protocols Arduino uses. It would be really neat if it had the ability to decode an Ethernet frame. (But for that I have Wireshark.)
My goal is to show these kids how hackers can hack ther Arduino projects by converts injecting traffic on the network buss. One of the projects I think I might have them make with the Arduinos because we have the IR module is the TV-B-Gone. Push a button and the Arduino sends out all TV off IR codes. (Nice little hacking project.)
Will the kids be touching the mains? No, but them I’m not watching them 24 hours a day. Will I teach them mains safety? Yup.
Will I be attaching the scope to the mains? I was thinking about it. But in my “junk” box I remember I have a doorbell transformer. 120 VAC to 24 VAC. Perfect for displaying a sine wave. Transformer not only steps downl, but isolates. Thank you some one in the forums who suggested that.
Quick question on the scope. I seem to remember being taught that scope can display current over time. With the Rigol scope I have can I display current? (Or am I mistaken?)
Thanks.