Products > Test Equipment
Bandwidth check of my oscilloscope with simple means ?
tggzzz:
--- Quote from: Elasia on December 11, 2020, 12:26:42 pm ---The best way to measure just the scope itself is to get one of leo's pulse gens you can directly attach and once you have a reference you can then attach your probes and see what they are rated for.
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Direct attachment also avoids the VSWR issues associated with the mismatch to 50ohms//15pF. There's a reason probe cable is very lossy :)
Such step generator tools are (arguably) more valuable in that they can show you the consequences of poor probing technique.
--- Quote ---You can also check things like bnc cables... half the time people dont know just how horrible they are. On the other hand most of this is moot if you are dealing with 100MHz and lower
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Coax (and other) transmission lines have a well-defined attenuation-vs-frequency characteristic, and the attenuation rises quites steeply with frequency. Pity the engineers that had to span the Atlantic ocean with coax cable; the repeaters had a lot of high frequency pre-emphasis. (Plus the TAT7 cable's impedance was unavoidably 61.8ohms, IIRC)
vk6zgo:
--- Quote from: 2N3055 on December 11, 2020, 10:42:56 am ---This is second topic with exactly same question from OP.
This one also devolved into discussion about creating fast pulses, like most of them..
Again, answer to OP question, no, there is no simple improvised way to measure -3dB point of scope front end without leveled signal generator.
If you had 200-500 signal generator with decent amplitude accuracy across the frequency (like SDG6000X or similar) you could fairly well estimate what the curve is.
OP never explained what he wants to accomplish or why he asked the question. Without that it is hard to help him.
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If you have a decent VTVM with an RF probe, you can look at spot frequencies across the band of interest, adjusting the signal generator to the same level for each spot, which is how we did things back in the day, when absolute accuracy of sig gens was more the exception than the rule.
The beauty of it is that the device you use to check the level doesn't need to have high absolute accuracy, just good frequency response accuracy.
Of course, if you had an RF probe for use with a DMM, with a known accuracy, you could do the same.
PS:-You could also use the precision detector Berni referred to in the edit to his post 18.
radiolistener:
--- Quote from: Fungus on December 11, 2020, 10:53:54 am ---Here's the results from a coin cell battery held like this:
The capacitor was 100% necessary to get a good time. Without it I was getting results in the uS range.
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Here is my result. I connected lab PSU with 12.9 V to oscilloscope BNC with 1 meter wires with banana jacks. :)
Lab PSU has some uF range capacitor on the output.
I think this happens due to wire inductance.
radiolistener:
--- Quote from: Berni on December 11, 2020, 10:50:18 am ---For going faster i would recommend just buying Leo Bodnars fast pulse generator:
http://www.leobodnar.com/shop/index.php?main_page=product_info&products_id=295
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Nice device, I want it, but very expensive.
tggzzz:
--- Quote from: Fungus on December 11, 2020, 10:53:54 am ---Without it I was getting results in the uS range.
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How do you use your scope to measure conductance?
(That's a pet peeve of mine)
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