Products > Test Equipment
Basic scope requirements except need to see ~10 ns pulses
stephencox:
--- 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, this would definitely be fine. Anything I have that is over 3 kV at least *should* be a constant voltage.
--- Quote from: shapirus on March 06, 2024, 08:23:10 pm ---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.
--- End quote ---
Thanks, this is interesting . . . I am not sure what to make of the budget vs. quality brand debate for this particular purchase. Depending on what you read, brands like Rigol are either a great value and pretty decent to use for anything that doesn't require critical calibration/certification, or are lousy, buggy, and failure-prone pieces of junk with terrible UI. Seems like there's a missing middle for my part of the market, which I know is true for lots of sectors (microscopes come to mind).
--- Quote from: blackdog on March 06, 2024, 08:40:00 pm ---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
--- End quote ---
The multiplier pulses I would always be measuring with a coax connection directly to the scope, but maybe I should be thinking more carefully about how I split the signal when I need to do this with the other electronics still attached.
tautech:
--- Quote from: tggzzz on March 06, 2024, 09:00:48 pm ---
--- 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?
--- End quote ---
No derating @1kHz. :P
From the manual....easier than copying the graph:
39KV:1KHz /20KV:10KHz /5KV:100Hz /300V:100MHz
tggzzz:
--- Quote from: blackdog on March 06, 2024, 08:40:00 pm ---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
--- End quote ---
Have you used a resistive divider probe, a.k.a. a Z0 probe. Passive, multi GHz.
If the source impedance is 450ohm, just connect the source directly to a 50ohm input and you have a *10 probe (950ohm *20 probe, etc).
With low end scopes, make sure it is a real 50ohm input. Just putting a 50ohm resistor in parallel with a 15pF capacitor is inadequate. Use a pad if necessary.
bdunham7:
--- Quote from: stephencox on March 06, 2024, 09:07:35 pm --- Depending on what you read, brands like Rigol are either a great value and pretty decent to use for anything that doesn't require critical calibration/certification, or are lousy, buggy, and failure-prone pieces of junk with terrible UI. Seems like there's a missing middle for my part of the market, which I know is true for lots of sectors (microscopes come to mind).
--- End quote ---
Both can be true even for a particular model depending on what the user needs and how they use it. The 'missing middle' is actually there in the mid-to-higher end offerings of the B-brands (Rigol, Siglent, GW Instek) and if you just skip the entry-level stuff trying to compete in the $500 price space you'll avoid most of the commonly complained about issues. If you want to spend less than $500 for what is often a fairly capable instrument, you'll just have to put up with some issues.
--- Quote ---The multiplier pulses I would always be measuring with a coax connection directly to the scope, but maybe I should be thinking more carefully about how I split the signal when I need to do this with the other electronics still attached.
--- End quote ---
Then be aware that a lot of the lower priced scopes do not have 50-ohm inputs, which is really a necessity for what you are describing with or without probes being used.
tautech:
--- Quote from: stephencox on March 06, 2024, 05:00:33 pm ---I work with electron multipliers and need to be able to look at 10–1000 mV pulses with a rise time of 1.5–3 ns and a total pulse width of ~20 ns.
--- End quote ---
Hardly challenging with a modern DSO......
1kHz rate 20mV 20ns pulse with 2ns edges ex SDG6022X AWG.
100 MHz DSO with BNC connection.....
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