Products > Test Equipment
Basic scope requirements except need to see ~10 ns pulses
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shapirus:
FWIW, as an example, here's what I am able to capture with a Rigol DHO804 tricked into thinking that it's a DHO924. Cost $342.16 at the time of purchase, but I did use some Aliexpress sale coupons active at that time.


1. A ~10 nanosecond pulse:




2. The shortest pulse that it can capture and detect its true amplitude (of course including the overshoot), meaning there's at least one sample point present at the peak:




3. About the shortest pulse that it is able to trigger on; here the displayed amplitude is below the true value (vertical scale is the same, but I raised voltage of the signal source to output ~5 V):

(I am not sure whether I hit the limitations of the scope or of the pulse generator here, but naturally I would expect that it's the scope, because it's clearly about the spot where 1.25 Gsa/s becomes the limiting factor)




As you can see, it has no issue triggering on a 1 kHz repetition rate. As a matter of fact, it happily triggers on a 0.1 Hz signal:




All of the above was captured using a 100:1 probe, so ~25 mV on the scope input. It can trigger on lower values just fine, but I haven't tested how low it can go when the pulses are very short.

I also haven't tested it on capturing two consecutive short pulses, but really there's no reason for it to be able to capture one, but not two.

A caveat: this was captured with a single channel being active. When you switch on another one, sampling rate is halved, and the results become accordingly worse.

Now, I'm not saying that it's necessarily a good idea to get, for scientific work, a scope like this, for which the observations you want to make are not very much above the limits of its capabilities, but I do want to point out that a multi-thousand dollar scope is not necessarily a strict requirement. I think it's the probes that you'll need to spend most of the money on, at least as soon as it comes to high voltage and/or differential probing.
tggzzz:

--- Quote from: tautech on March 06, 2024, 07:58:27 pm ---39kV 1000:1 2pF 50 MHz 900M \$\Omega\$ HVP-39pro fits the bill.

--- End quote ---

Make sure the voltage vs frequency derating curve is acceptable :)
tautech:

--- Quote from: tggzzz on March 06, 2024, 08:31:22 pm ---
--- Quote from: tautech on March 06, 2024, 07:58:27 pm ---39kV 1000:1 2pF 50 MHz 900M \$\Omega\$ HVP-39pro fits the bill.

--- End quote ---

Make sure the voltage vs frequency derating curve is acceptable :)

--- End quote ---
OP states:
like kHz or slower
blackdog:
Hi,

Good pulse response is not possible with passive probes.
I have several 500MHz probes and none of them have as few abberations as a good coax connection.

Coax type
If possible, then always use good 50 Ohm coax, normal RG58 is not good enough for correct pulse response.

Bandwidth
I am thinking more of a 500MHz model scope with at least 2GHz sample frequency.

My 2 cents :-)

Kind regards,
Bram
tggzzz:

--- Quote from: tautech on March 06, 2024, 08:36:39 pm ---
--- Quote from: tggzzz on March 06, 2024, 08:31:22 pm ---
--- Quote from: tautech on March 06, 2024, 07:58:27 pm ---39kV 1000:1 2pF 50 MHz 900M \$\Omega\$ HVP-39pro fits the bill.

--- End quote ---

Make sure the voltage vs frequency derating curve is acceptable :)

--- End quote ---
OP states:
like kHz or slower

--- End quote ---

Yes. So?
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