Oscilloscopes for electricians

[rexxar]

Hello all. My teacher has asked me to make a few videos explaining oscilloscopes, and I'm not quite sure what I should include.

Long story short, I mistakenly enrolled in an electrician's class instead of an electronics class and can't drop it. I can go over basics, but I can't think of any particular application an electrician would have for an oscilloscope. Voice and data is also part of the program, but I'm not sure where an oscilloscope would be useful in that field either. 

Does anyone in the field have a use for oscilloscopes?

Really I'd just point him to Dave or W2AEW's channel, but he's given me this assignment in lieu of doing electrical work at one of the college admin's house, which I rather don't want to do...

[Phaedrus]

An oscilloscope can be used to check for noise on the mains voltage, which could help indicate faults. It could also be used for voice/data connections to check integrity and frequency of data signals.

[128er]

Hi rexxar,

im an electrician, quite young, but i am . Not especially electronic guys need oscilloscopes. Electricians need them to proof the quality of the mains. Looking for spikes, or proof the mains for harmonic distortion. Often we use it for long-term records over many hours or days. Such faults are often infrequent an maybe comes from a faulty or wrong dimensioned load. These scopes are most slightly different with regard to memory (for long-term records), they are build for higher power categories, battery powered with insulated inputs, etc. ...

I hope that gives you a little overview. You can look on the internet for "mains analysis", for example. There are many applications for electricians

[Fank1]

I used them frequently to adjust dc motor drives and SCR soft starters.
Back when it was all analog.

[Legion]

You mentioned data in your post. Some digital scopes like the Rigol DS2072 can interpret common communication standards like I²C. This guys video shows some of the I²C functionality.

[ajb]

A two channel scope with a current probe and the right math functions could make for a very informative illustration of power factor.

[deth502]

i cant help you.

i know just enough to be dangerous with electronics, but ive been wiring and doing electrical work since i was a teen. ive also installed tons of voice and data networks (no software, just a hardware guy) ive done everyting from single phase houses to 3 phase industrial/commercial electric, and have never once had the need for a scope, not even a little.

i do have a phase indicator, or phase rotation meter, or whatever you want to call it, to determine which leg of your 3 phase is which, maybe, and this is a big stretch, but just maybe you could argue that a 3 channel min scope could perform this task, but imo, its impractically over complicating it.

now, if you had asked about a scope use in auto repair, thats another story. hundreds of uses there.

[AG6QR]

Voice and data is also part of the program, but I'm not sure where an oscilloscope would be useful in that field either. 

An electrician or installer might use one to tell whether an inverter or uninterruptible power supply is a true sine wave inverter or a "modified sine wave" version (should be called modified square wave, there's nothing sine-like about it).  I'm not sure how often electricians need to work with inverter/UPS outputs, but at least that's a very basic application that any electrician ought to understand and appreciate.

As far as voice goes, it can be used to determine when an amplifier is clipping.  Car stereo install technicians often use a simple one-channel portable oscilloscope to set the gain on an amplifier so that it just avoids clipping.  Search the web for uses of a "TPI 440", and you'll find plenty of people using that model for just that purpose, probably because it's just barely good enough to do that job, and not really good enough to do anything more complex.  I don't know if that's within the scope of your target audience, but it's a use.

[deth502]

Search the web for uses of a "TPI 440", and you'll find plenty of people using that model for just that purpose, probably because it's just barely good enough to do that job, and not really good enough to do anything more complex. 

wow, just searched that. that seems like a hell of a lot of money for what it is. looks like it dosent even have a bnc input, just graphs the voltages from the dmm probes. ive got a small pos crappy lcd scope that i paid just over 100 for that looks just as good or better than that for $350+, and it has a bnc input! i cant see why anyone would buy that when you can get one of those dso nano's for under $100.

[HackedFridgeMagnet]

You could check power factor and distortion with an oscilloscope. Also frequency.

Inrush current.

[AG6QR]

wow, just searched that. that seems like a hell of a lot of money for what it is. looks like it dosent even have a bnc input, just graphs the voltages from the dmm probes.

Agreed.  Its bandwidth is 1MHz, so it hardly needs BNC at that frequency.  OTOH, its input IS isolated, which makes a few specialized types of tasks easier than they'd be with a "real" scope.

I own one, I'm ashamed to say.  I bought it about 15 or more years ago, I don't remember exactly.  At the time, it was much cheaper than a proper scope.  But the market has changed a lot in the intervening years, and that model has not kept up.  I don't understand how it can still be sold at anything approaching that price.  I do not recommend it at all.  Not only does it have a lack of features, it has very poor ergonomics on those features which it does have.  By today's standards, I'd call it a $50 multimeter combined with a poorly implemented crude and slow waveform visualizer.

[NiHaoMike]

Once (many years ago), I had an issue with my Internet service. I called up the ISP (Windstream) and they sent someone who connected a portable scope (or something, might actually be a spectrum analyzer) to the line and diagnosed it as a corroded connection somewhere underground.

On an unpowered copper cable, a scope can be used as a TDR to estimate where a problem with the line exists and where to start looking for the fault.

There's also an article about using a scope and a current clamp to check the bearings in a motor without disassembling the machine. An uneven spot from a damaged bearing causes an unusual amount of harmonics at the motor shaft speed. (Related to it is how a Shannon Liu Quadrature Drive extracts the speed of a reciprocating hermetic compressor using only current sensors and FFT.)

[Rerouter]

A scope is also the best way to track and manage harmonics on the line (what your teacher may have called distortion)

equally between phases it can help show that there is too much reactive loading (phase offset by a few degrees, )

[nowlan]

make a few videos explaining oscilloscopes
Fluke make portable ones. But their examples/use case are absent on website

• General Purpose Waveform Analysis
  Industrial Machinery Testing
  Industrial BusHealth Troubleshooting
  Electronic Systems Troubleshooting

I think they are more basic electronic theory, explain:
AC/Rectification/DC.
Inrush current? Voltage sags. EMF/diode etc.

[pickle9000]

With a current clamp you can check many motor related items, loading, contact quality, brushes and certain types of winding faults (while the equipment is running).

Electricians often work around generators and other "off grid" items in those cases seeing the actual waveforms can prevent equipment damage before it happens. The low bandwidth scopes (1-5MHz) are just fine for this application.

[rexxar]

Okay, there's a whole lot more utility for a scope in this field than I thought!

I think I've got enough to get started. I'm not precisely sure what kind of data they're dealing with, it's probably mostly ethernet, but I'll show some RS232 signals. My DS1102e can't decode them, of course, but I'll just mention it.

It ought to be interesting to learn how to induce things like harmonic distortion and phase offset so I can demonstrate them.

Thanks a lot, everyone!

[NiHaoMike]

Use a light dimmer to demonstrate harmonics and a fan (or other motor) without a run cap to demonstrate phase offset. If you want to go advanced, get a small air compressor, take the FFT of the current, and then demonstrate how the harmonics of the motor speed go down in frequency (and increase in magnitude!) as you block the outlet and make the compressor work harder.

[Pillager]

My thoughts:

A garden variety electrician, who wires houses/flats and installs outlets wouldn't really need oscilloscopes. If he has to measure mains quality or the like, there are special meters for that.

Anything mor advanced, and there might be a need for oscilloscopes. At work, we use them to adjust sensors to a certain time window, we check dc rails for faults, check pulse widths, etc. Granted, my work has more to do with mechatronics, but we are called electricians 

As for the scope, we use a Fluke Scope Meter 96B. Anything similar is a good tool for electricians. Relatively light and portable are the main features. And not those small pocket DSOs, the small but not very usefull in that regard.

[G7PSK]

I am not an EE or electrician but I build and service gen-sets. I often use a scope for checking them, just looking at the output waveform can give you a good idea of the state of the AVR board. You dont even need to take measurements for this just a glance at the shape of the wave will tell you good or bad  and should it be replaced.

[deth502]

I own one, I'm ashamed to say.  I bought it about 15 or more years ago, I don't remember exactly.  At the time, it was much cheaper than a proper scope.  But the market has changed a lot in the intervening years, and that model has not kept up. 

indeed, with internet shopping, ebay, and the ability to buy cheap products directly from china, its a whole 'nother market that it was even 10 years ago.

back in the 90's youd be hard pressed to find the highest top level electrical tech with a handheld scope meter.

[pickle9000]

I am not an EE or electrician but I build and service gen-sets. I often use a scope for checking them, just looking at the output waveform can give you a good idea of the state of the AVR board. You dont even need to take measurements for this just a glance at the shape of the wave will tell you good or bad  and should it be replaced.

Current clamp stuff for engines, starting system, cylinder compression.