suggest basic func/signal generator for basic scope test/setup ?

Hi, You have a built-in calibrator in the 'scope. One I'd like will be multi wave form capable with variable frequency and out put level. If your set up means calibration, then the generator should be calibrated against known reference as well. I send in my 'scope to a lab to maintain it's calibration official.

How are you planning to verify that the crap you buy on ebay is giving a valid output? Anything without a recent NIST-traceable certificate is only adding more variables to your situation.

If you have doubts about the accuracy of your scope, take it to a metrology lab for calibration with NIST-traceable standards.

You need to be a lot more descriptive about what you're trying to accomplish. If you have other uses for the generator, use those criteria for your decision. If ALL you want is to calibrate the scope, forget it.

For calibration purposes, a generator won't do you any good unless it has the waveform precision you need and also has traceable calibration. You can't afford that.

It's a binary situation. If you use your scope in business, and maintain any certifications, you must send it in to have it done right.

For hobby use, my experience says that a TEK scope either works "close enough" or it needs fixed. A scope is a poor tool for making measurements. It's great for "looking at the waveform", but unless you have a scope with built-in counter and DVM, you won't get accurate measurements.

Here's how you check a scope. If it's a CRT scope, there are some things that mess up everything. Wrong high voltage can shrink or expand the display. A sure sign is if the display changes size when you change intensity. Make sure that's not a problem before you go tweeking stuff. Ditto for other power supplies, but the effects can be much less dramatic.

Do all the functions work? check. Does it trigger? check. Use a T-connector to put your DVM and a variable power supply into the vertical input. Compare deflection against your DVM. Check Stick a transformer from the AC line into the input. Wall wart etc. Does it look like 60 Hz. or 50Hz. depeding on where you live. You can check several sweep ranges. Find a known signal source. Crystal oscillator in your computer,

27MHz CB walkie talkie etc. Use that to check the faster sweeps.

Now comes the hard part. In a perfect world, frequency response and transient response are equivalent. In the real world, where you're looking at tranisents, I prefer to optimize transient response. Stick the calibrator output into your vertical input. (I'm assuming the scope has one. If not, skip the step. Most generators are worse than the scope.) If the corners are mostly square, you're done.

Don't open the case if you don't have the manual with calibration procedures and the equipment specified. You can substitute equipment, but your question suggests you don't have the knowledge to do that. Virtually any generator you pick will be worse than your scope. Just getting the waveform into the scope without degrading it is an art.

RESIST TEMPTATION TO MAKE IT PERFECT. YOU RISK MAKING IT MUCH WORSE. RESIST TEMPTATION TO LET YOUR BUDDIES TALK YOU INTO MAKING IT PERFECT. IF IT AIN'T BROKE, DON'T FIX IT. IT WILL NEVER BE PERFECT, DON'T EVEN TRY. If it's far enough out of calibration to need significant tweeking it's probably broke. Fix it before you try to calibrate it. Leave the covers on and enjoy your scope.

The above assumes the scope works and nobody's been inside messing with adjustments.

Scopes are great for looking at waveforms. If you need to know the frequency of something, use a counter. If you need to know the voltage of something, use a DVM.

mike designed scope calibration generators in a former life.

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Return address is VALID!

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to

for your

it.

I know just enough to realize that best option for calibration is... send it to a lab.

however, i want to be able to test my scope's range of functioning initially and (on occasion) then use the generator to inject signals into circuits that i might be hobbying with later (or any other usefullness)

unless it

and

done right.

just **hobby** use.... it would be a short lived, fault ridden business buying a abused scopes from the bay and trying to start some electronics related business with that equip.

these were purchased on hobby budget and will be used as hobby tools.

i would just like the peace of mind (on hobbyist budget) that the scope is not dead or way off on certain settings.... so , my thinking is to run scope through a range and combination of measurements to know if it gives the expected behavior (read, some close or near expected measurement/wave/func form )

"close

unless

accurate

The tek 2236 does have a built in autoranging DMM (w/frequency, period, width, 0-2G-Ohm meas, etc ) that can be used through a "separate" leads port or will display the measurements from channel 1 concurrently with CRT plus more stuff

everything.

sign

sure

dramatic.

my scope passes this test but i read "online researching" that the tek 2236 has virtually NO power supply isolation and the measurements get munged by it's own noisey power supply ??? anyone know about this

i have seen where there appears to be slight noise (small fuzzy waves and pulsing) in the sweeps and was wondering if this was the isolated power supply issue or another fault in the scope ?

into the

etc.

computer,

sweeps.

great, thanks for that, i will try those reccomendations ....

are

tranisents,

the built-in scope probe calibrator is what i used for first trace test and probe calibration ( 500 mv P-P 1 kHz )

FWIW the probe calibration gave picture perfect CRT image of over and under shoot wave form when turning the calibration screw on probe. that is leading edge of square wave turned up or down while rest of wave remained flat and steady ???

when adjusted the form was square, even width and flat across the CRT.

calibration

learned that lesson a while ago

thanks mike for taking time to help an amateur hobbyist, thanks for info and ideas

robb

for

Hey Jeff, can always count on you shooting straight, narrow and succinct.

i do not need traceable calibration

as an amateur hobbyist, i just want to put the new scope through wide range of measurements to see if there are any gross problems ... if scope measures close on varied ranges then i have peace of mind that scope is in fair working order.

so if i test an unknown scope with unknown signal generator and they both come close in agreement i think i can be

**statistically** comfortable that both are in close enough for hobby work condition. if they do not agree well then i can use some other means to test signal from generator then go from there.

this is part of the hobby :) i have 2 x 2236 for scopes from the bay.... a scope and parts spare for under $90 (*delivered*) one appears to be functioning well, the other maybe working well and that suits my hobby budget

calibration is what... $150 ? thats more than the two and shipping combined

thanks again for the response, thoughts and straight shooting robb

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for

be

level.

yes, calibration test, but just for peace of mind and something to test the range of the scope i would not change anything or tweak if the scope was close, maybe attempt a repair if grossly out of spec

calibration would likely cost much more than i paid for the scopes including delivery.

thanks for reply , rob

If you want to test the time base at the low end, you can use the signal generator from my Daqarta software with your sound card. Sound cards use crystal time bases, so you get pretty decent accuracy. At a sample rate of 48000 Hz the max sound card output will be under 24000 Hz, so you won't be able to calibrate below 50 usec per division. At the low end there is no particular limit, since the generator maintains the timebase accuracy for as long as you want to wait. (Of course, you need to use a pulse or square wave to pass the sound card's AC coupling cap.)

Daqarta also has a wide variety of available waveforms, including different kinds of noise, plus you can provide your own Arbitrary waveform or even play a WAV file.

Sound cards have no intrinsic amplitude calibration... they are perfectly repeatable, you just don't know what the attenuator steps are, or the full-scale range. Daqarta has an Auto-Calibration feature to figure out the attenuator steps, but you need something external to calibrate full scale. But once you do that, you're all set. The attenuation range is usually quite wide (more than 60 dB) and you can also change the size of the digital waveform to take that even farther... 90 dB is fairly easy to get.

By the way, the Daqarta signal generator is FREE. At the end of 30 sessions or 30 days, the input capabilities will stop (unless you purchase), but the output and analysis capabilities keep on working. You are welcome to use it forever like that.

Best regards,

Bob Masta DAQARTA v3.50 Data AcQuisition And Real-Time Analysis

Scope, Spectrum, Spectrogram, Signal Generator Science with your sound card!

Or: holding a bare wire or unbent paper clip, touch it to the input. Look for 50 or 60 Hz as appropriate.

Mark

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thanks Bob, it maybe enough to give me piece of mind ?

thnaks for reply, robb

Krohn-Hite 1400A...very cheap good quality. does sine square triangle. It can also sweep frequency and amplitude.

Krohn-Hite makes very good oscillators and have been in business for many years.