Author Topic: Using Probes with different bandwidth on same scope Yay or Nay?  (Read 1773 times)

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Offline noidea

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This may be a dumb question but I have searched the forum and net and can't seem to find an answer so here goes. I'm a scope newb and know that your probes should have a higher bandwidth than what you are trying to measure but if you have a two channel scope does it make a big difference if your probes are different bandwidth?

The scenario is I have a Fluke 106C 100Mhz scopemeter and one of the VPS210 200MHz probes is dead (it's open circuit, I'm happy to try and take it apart for the forums enjoyment if you want)

Fluke accessories are "rather expensive" in Oz and a VPS210-G 200MHz probe is $399 ex GST from RS components but the probe for a 190 Series II Scopemeter VPS410-G which is a 300MHz probe with higher CAT ratings is only $293 ex GST. I then did a bit of searching for other isolated probes and worked out the Fluke Probes are about 99.999% to really be Multi Contact Isoprobe III series and I can buy a 300MHz or 500MHz probe from RS for around the $150 mark, which seems like the way to go.

At the moment the signals I am measure are in the range of 10kHz with a 10V peak to peak so all of these probes are way more than I need but if I use a 200MHz probe in one channel and a 300 or 500 MHz probe in the other channel is it going to make a huge difference? I would rather not have to buy two new probes if I only need to buy one.

 

Offline c4757p

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Re: Using Probes with different bandwidth on same scope Yay or Nay?
« Reply #1 on: June 03, 2015, 04:23:41 pm »
You're fine. The probes have a higher bandwidth than the scope anyway, so they have practically no effect on the overall bandwidth. If that weren't the case, the bandwidth of each channel would just be determined by the bandwidth of the probe on it.
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Offline tggzzz

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Re: Using Probes with different bandwidth on same scope Yay or Nay?
« Reply #2 on: June 03, 2015, 04:47:08 pm »
You should be OK.

Sanity check: put all the probes on the same point, and see if the displayed signals are identical.
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Offline w2aew

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Re: Using Probes with different bandwidth on same scope Yay or Nay?
« Reply #3 on: June 03, 2015, 07:50:42 pm »
The only gotcha you might run into when using higher BW probes on a slow scope is that the compensation range might be insufficient to properly compensate the probe.  If you're able to properly compensate the probe, then you'll be fine.
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Offline noidea

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Re: Using Probes with different bandwidth on same scope Yay or Nay?
« Reply #4 on: June 04, 2015, 12:16:32 am »
Thanks all for the information and heads up about compensation I think it might be wise to stay with the 300MHz options.
I'll report back about the probe compensation when I get the new probe.
 

Offline tggzzz

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Re: Using Probes with different bandwidth on same scope Yay or Nay?
« Reply #5 on: June 04, 2015, 08:35:28 am »
Thanks all for the information and heads up about compensation I think it might be wise to stay with the 300MHz options.
I'll report back about the probe compensation when I get the new probe.

Put the probes on the same point and see if there is any difference; subtract one signal from the other. If no difference then you don't have a problem.
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
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