Lister Engine Forum
How to / DIY => Everything else => Topic started by: lendusaquid on December 07, 2008, 09:57:45 PM
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I have just been given an Oscilloscope and have not a clue how to use it.Out of curiosity i would like to see the wave form from my gen.How do i set it up?
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What is the make and model of your Scope ? Did you get probes with it ? If so , how are they marked ? Basically you use the vertical amplifier to feed the signal to and use the horizontal frequency control to synch the input signal and display the waveform. You need an attenuated probe to reduce the 240 volt's you will be using as the input and start with the vertical input at max attenuation and then reduce to get a good signal amplitude on the display.
I can go through a detailed sequence if you need more info.
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I would echo the words of caution
These may or may not be helpful.
Regards,
http://www.doctronics.co.uk/scope.htm
http://www.facstaff.bucknell.edu/mastascu/elessonsHTML/Measurements/Scope1.htm
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Its a Hitachi Model V-212 and the only lead i have has a couple of crocodile clips on the end of it.I shall take a look at those web sites.
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Get scope probe or two. Not very much (around 20-50-60 each depending on bandwidth and brand type).
MUST, must get isolation transformer and "break" the ground on scope's side.
Cheers, Wizard
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Get scope probe or two. Not very much (around 20-50-60 each depending on bandwidth and brand type).
MUST, must get isolation transformer and "break" the ground on scope's side.
Cheers, Wizard
Just to help clarify the good advice given here by Wizard. What you will be doing is hooking up the two scope leads to live AC power for some of your measurements. Since the shield/ground terminal on the scope input (the outer ring of the BNC scope probe input receptacle) is attached to the metal frame and cabinet of the scope that entire instrument will become 'hot' with mains power during some tests if the shield lead is connected to a hot terminal. It is for this reason that extreme care must be employed when doing such measurements. The scope itself has to have isolated power. Power it from an isolation transformer rather than hooked directly to the mains supply. Make sure the third power cord pin (ground) is not connected to anything so the scope case can 'float'. Place the scope on a dry piece of plywood or other suitable insulator when using it for these measurements. Make sure you are wearing dry, rubber soled footwear and are also standing on an insulating surface. Avoid touching the case of the scope when making knob adjustments. This assumes the scope has insulating plastic knobs! Keep one hand in your back pocket so you cannot accidentally rest it on a grounded surface and electrocute yourself. BE AWARE AND BE CAREFUL. THINK THROUGH YOUR ACTIONS BEFORE MAKING THEM.......ALWAYS.
Limit your waveform tests to 120 volt circuits or less. Higher voltages start to create unexpected undesireable and not necessarily intuitive behaviors to the novice, plus are increasingly dangerous.
Even with a X1, X10 scope probe you will need to reduce the voltage to the probe with an additional series resistor placed in series with the probe input and the AC power terminal being examined. I suggest obtaining a 10 meg ohm, 1/2 watt resistor. This will reduce the voltage that the scope probe is subjected to saving it from possible burnout. Note that you will lose absolute voltage alibration accuracy but that is not what you are doing with the scope anyhow, you are more interested in the waveform shape which will not be compromised. We have voltmeters for voltage measurements.
If you are a novice in working with electricity try to find a experienced person who can mentor you in person or walk you through these tests the first time. Good idea to always have a buddy present when working with this stuff too!
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Have to admit I was being a bit casual in my information , the result of years of abusing safety rules by a practicing technician !!
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If say i plugged in a 12 or 24 volt transformer to my gen supply and tested the output, would i get an accurate picture or would the transformer alter the wave in some way ?.
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Depends on how good the TX is , but most will affect the shape of the waveform to some extent.
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:o
I've been prodding around inside switching PSUs with my 'scope (looks similar in functionality to the OPs - mine is a Telequipment D54, I think), with readings of over 400v, with no isolation transformer or grounding of any particular description. and yes, I would have been twiddling some of the adjustment knobs while plugged into such voltages.
As I say: :o
Still alive so far, must be more by luck than judgement...
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Get scope probe or two. Not very much (around 20-50-60 each depending on bandwidth and brand type).
MUST, must get isolation transformer and "break" the ground on scope's side.
According to Tektronx (http://www.tek.com/Measurement/cgi-bin/framed.pl?Document=/Measurement/App_Notes/Technical_Briefs/tds3000-float/eng/safety.html&FrameSet=oscilloscopes), you must absolutely never use an isolation transformer ???
Of course, that may only apply to Tek 'scopes - I know they are seriously expensive, so maybe thay have excellent built-in protection.
Edit: More info -
Floating An Oscilloscope: A Definition
“Floating” a ground referenced oscilloscope is the technique of defeating
the oscilloscope’s protective grounding system – disconnecting “signal
common” from earth, either by defeating the grounding system or using an
isolation transformer. This allows accessible parts of the instrument
such as chassis, cabinet, and connectors to assume the potential of the
probe ground lead connection point. This is dangerous, not only from the
standpoint of elevated voltages present on the oscilloscope (a shock haz-
ard to the operator), but also due to cumulative stresses on the oscillo-
scope’s power transformer insulation.
This stress may not cause immediate failure, but may lead to future danger-
ous failures (a shock and fire hazard), even after returning the oscilloscope
to properly grounded operation!
Not only is floating a ground-referenced oscilloscope dangerous, but
the measurements are often inaccurate. This results from the total
capacitance of the oscilloscope chassis being directly connected to the
circuit under test at the point where the common lead is connected.
Download (http://www.cbtricks.com/miscellaneous/tech_publications/scope/floating.pdf) the PDF that quote is taken from.
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That probably means that an Iso TX should never be used to power the scope.
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Reminds me of that saying , "If the only tool in your box is hammer , pretty soon everything looks like a nail" LOL !!
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I'm aware of this issues, for my work where I examine stuff all the time and use scope often, my scope is just directly plugged and plug all the stuff I work on either to test or to look at through isolation transformer.
In your particular situation with checking waveforms on generators/alternator/etc, need to have scope floating or route the isolation transformer from generator output and monitor the waveforms on the output side of transformer's. All the transformers actually reflect what waveforms is generated to mostly degree. Even a wall wart tranformer that outputs AC not DC is excellent way to monitor the quality of waveforms and give you cheap isolation to boot.
Cheers, Wizard
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lendusaquid
I have a model V-509, which I was looking into new probes for, and it is similar to the Hitachi Model V-212.
If you need probes and/or manual, I finally found my links to these sources.
http://www.probemaster.com/shop/article_info.php?articles_id=5
http://www.probemaster.com/shop/advanced_search_result.php?keywords=4904-2&search_in_description=1&x=62&y=12
Price seems hight to me though!
Scanning the list you take the same master kit as mine apparently.
number 4904-2
0-1-2-3 pages for the manual. Have to click the numbers to start the load,
took me a sec to figure that out and I had a bit of trouble with them in firefox, but they do work.
http://www.eserviceinfo.com/downloadsm/16944/Hitachi_V211.html
They are in rar format so if you don’t have winrar, here is a 40 day trial de-compressor
http://www.download.com/WinRAR/3000-2250_4-10745708.html
I also found this interesting discussion on oscilloscope grounding.
http://www.electronicspoint.com/oscilloscope-grounding-question-t113920.html
http://www.marcspages.co.uk/pq/4120.htm
Hope some of this stuff helps.
obfu
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I suggest you read up on the grounding and safety issues. Please be safe....
I still own a V-212. Bought it new 20+ years ago.
Not a bad little no frills 2-channel scope. I've put lotsa mileage on mine. If you have any specific questions about it let me know.
Here's the operators manual:
http://www.weirdstuffwemake.com/sweetwatergems/electronics/misc/Hitachi_V212_Operation_Manual.pdf
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Thanks for all the links and the manual. Ive got a lot of reading to do now.I would like a step by step how to do it if possible to satisfy my lack of patience and curiosity,if possible.Ive also just been given an Avo 8 which looks nice enough to put on display.A local college is shutting down a department and throwing all this gear in a garbage skip.A mate of mine works at this college and is raiding the skip for anything he can find. Much happyness :D
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.....throwing all this gear in a garbage skip.
And these guys are supposed to be teaching young folks? :P That oughta be criminal.......what a waste.......
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Thanks for all the links and the manual. Ive got a lot of reading to do now.I would like a step by step how to do it if possible to satisfy my lack of patience and curiosity,if possible.Ive also just been given an Avo 8 which looks nice enough to put on display.A local college is shutting down a department and throwing all this gear in a garbage skip.A mate of mine works at this college and is raiding the skip for anything he can find. Much happyness :D
Nice 1 !! Any nice variable DC lab power supplies going ??!!
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Thanks for all the links and the manual. Ive got a lot of reading to do now.I would like a step by step how to do it if possible to satisfy my lack of patience and curiosity,if possible.
OK, here's a quick run down on the controls on your V212. Maybe it'll help get you started where to set the knobs to look at the output of your generator. These descriptions are kind of "basic" and geared towards looking at a120VAC and 50/60Hz generator output. Sorry if If I've made any errors. As always, the info in your Operators Manual is best.
I won't repeat the safety issues about grounding (or ungrounding) or using isolation xformers or whatever. Please be careful is all....
Here we go...
ON/OFF button. Pretty self explanatory.
Next down, there's a hole for trace rotation. You can stick a screwdriver in here and adjust the trace so that horizontal is correct. Leave it alone for now.
INTENSITY. How bright it is. (duh) Try and use the lowest comfortable brightness. Excess intensity for long periods of time can "burn" the phosphor on the screen and leave dark areas. Start about 1/2 way up and adjust to taste.
FOCUS. Once the scope is fully warmed up, adjust to get the narrowest, sharpest (least fuzzy) trace.
TIME/DIV. This sets how long it takes the trace to sweep horizontally. The graticule on the V212 is 10 divisions wide and 8 divisions high, so if you set the Time/Div to 1mS, it will take 1millisecond to sweep across 1 division, and 10 milliseconds to sweep across the entire face. Since 50Hz equals 20mS per cycle, a Time/Div setting of 2mS would result in a 50Hz sinewave just filling the entire screen horizontally. A slower setting (5mS/Div) would show more complete cycles on the screen and a faster setting would stretch out the waveform to see less cycles but detail. Start at about 5mS/Div and play from there.
VOLTS/DIV. This sets the vertical amplitude... how many volts it takes to move the trace vertically.
So, 120VAC(rms) = 170volts peak, or 340 volts peak to peak. So with a setting of 50V/Div, a 120VAC(rms) [340Vp-p] sine wave would span nearly 7 vertical divisions. If you used a 10X scope probe, which divides the signal amplitude by 10, then you would use 5V/Div to get the same results.
Note that there are 2 Volt/Div knobs, one for each channel.
AC coupling switch. This 3 position switch has AC, GND, and DC settings.
On "DC", signals are shown "as is" and the scope can measure AC as well as DC signals.
On "AC", the signals are AC coupled, which means that any DC component is blocked. This is handy for looking at AC signals that ride on top of a DC level. Like looking at "noise" from the output of a car alternator, where there may be a few hundred millivolts of AC noise that rides on top of a 12 - 15VDC battery voltage.
For looking at the output of your AC generator, you can use either the AC or DC setting, since there should be no DC component to the signal.
"Ground". This simply grounds the scope input and allows no signal to pass. This is handy for momentarily killing the signal so you can set where the trace is (vertically) with no input.
There's one of these switches for each channel.
SWP VAR. The variable sweep knob allows you to fine tune the sweep rate and It's effect is similar to the "TIME/DIV" knob except that it''s infinitely variable instead of the finite (and accurate) steps of TIME/DIV.
Note that if SWP VAR is in any position except the far clockwise "cal" position, the actual TIME/DIV shown will not be accurate.
POSITION (vertical) Sets the vertical position of the trace. For measuring AC signals, centered vertically is usually best.
POSITION (horizontal) sets the horizontal position of the trace. Pulling the knob out expands the trace 10X. You'll mostly use with the knob pushed in. (normal position)
MODE has 5 positions... CH1, CH2, ALT, CHOP, ADD.
If you only have 1 scope probe, then you will only need to use CH1 (or CH2 if you prefer). ALT, CHOP, ADD are for displaying signals from both channels (2 probes) at once.
INT TRIG Internal triggering. Just leave it set to whichever input channel your iprobe is on (probably CH1)
LEVEL This sets up the trigger level. If you look at your signal on the scope and it appears to be "scrolling" horizontally, then you need to adjust the trigger level to "freeze" it in place. Once you've got the motion stopped, then you can fine tune the trigger level to set where in the cycle (what voltage level) the scope starts it's sweep from. Play with it and see....
SOURCE (trigger) Mostly just leave it set to "Int" for general work.
CAL 5V This little post has a 5 volt peak to peak square wave on it. As I recall it's about 1Khz.. Connect your scope probe to it to verify vertical calibration.
Errr... I think that's about al the controls on the face that you need to think about to start with. You've got a link to the Operators Manual for "the bigger picture".
Let me know if you have any other questions about your V212
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Thanks Steve thats just what i needed to get me started.Ill still gen up with the manual but what you have written has made things a lot clearer.
Compig
All i got given was some low voltage soldering iron supplies with some soldering irons.
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I agree - ground the scope and plug into wall power but make sure the generator is not grounded.
Do most people ground their generators? For small portables, I've never bothered with it.
An AC transformer to reduce the voltage should give you a good idea of what the waveform looks like.
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I stumbled onto these two scopes on craigslist, and bought both of them for only $15.00 yesterday. I have had no luck
finding any manuals for them, I guess, do to their age. Can anybody point me to O-scope 101 for dummys?
I have never used one in my life. I just want to be able to use them to check my ST head when I get it up and running.
The older I get, the more stupid I tend to think I am!
(http://i52.photobucket.com/albums/g18/OldBellows/scp1.jpg)
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Good God I have not used one of those things in decades... 1989?
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For most basic work and troubleshooting, an hand held single channel digital 'scope is cheap and effective. The ability to capture a waveform is VERY handy for slow speed signals or for non-repeating events, which an analog scope just can't show you. That plus fitting in your tool box, portability and no AC needed is a huge plus.
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Lots of good information right here in this thread - I will especially direct your attention to the safety information covered here. Don't kill yourself or your generator! Most scopes have the ground lead tied to the metal chassis - that can result in rather unpleasant things happening if you connect the ground lead to anything that isn't grounded. There's also a couple of links in the 3rd post that still seem to work - I didn't check them for accuracy but just a quick look seemed like they explained things.
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;D Thank you for the advice gentlemen. I would like some suggestions as to a handheld digital yall would
recommend. I guess it comes from being a reenactor, Blacksmith etc. , but I own more old school tools than modern
ones. I have a soft spot for good old used tools that gets the best of me! :o My late Mother always told me I was
born into the wrong century...
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If you have a laptop and a small tool budget:
http://www.amazon.com/SainSmart-Portable-Handheld-Oscilloscope-Bandwidth/dp/B00FYGEFYM/ref=sr_1_2?ie=UTF8&qid=1457207292&sr=8-2&keywords=usb+oscilloscope
I prefer to use a stand alone unit. Mine is an obsolete Velleman. I think today I'd try out one of the SainSmart or similar units.
Velleman's scopes are decent and reliable also.
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If you want to learn about oscilloscopes, one option is to get a small power transformer with a low voltage output - 6 or 12 volts works well and is "safe". Connect the primary to insulated leads to the mains, and feed the secondary into the "vertical" input on your scope. You should be able to play with the 'scopes you have and synchronize a nice sine wave on the display. It will at least get you a feel for what you can see and how the various knobs work on the scope.
Have fun, stay safe!