View Full Version : Parallax PC Scope

02-19-2007, 08:57 AM
I am considering purchasing the Parallax PC scope and was hoping someone can answer a few questions.

1) I plan on using it for small induction motor analysis (1/4 to 1/2 hp)
Will 10x and 20x probes work with the Parallax device?

2) If the sources I'm working with are grounded neutral (residential) is there any risk in not using a differential probe?

3) Would it be worth while upgrading the probes by getting som banana to BNC adapters ?

The price is so nice and I don't need an awesome sample rate for what I'm working with (everything <20khz) so the device seems perfect for my needs.

Thanks for the help!


02-19-2007, 11:10 PM
As far as I know, you cannot use any other probes than what is provided.
Also make sure there is no ground differencial between the PC and what you are testing.


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02-20-2007, 12:37 AM
This is limiting.

I am not doing much electronics work.· Primarily I will be working with motor windings (170Vpp and some 340Vpp mostly 60Hz some PWM stuff at 16kHz) so I need to measure lead, lags, transients, etc...· I don't need a mac daddy scope with the ultimate sampling rates and bandwidths.· The PC scope has all the functionality I need at an unbelievable price.· The only thing that has kept me from purchasing right·right away is·the published max input voltage of 20Vpp.· If I can use a banana to BNC adapter·with 10x and 20x probes I am in business.

John R.
02-20-2007, 12:38 AM

The scope is only good for 20V P to P. there have been some posts in the sandbox (I beleive) on how to make a "10X" adapter. It's not too complex, but dooable. The problem with using the scope with higher voltages is that the isolation from the PC is not as good as it could be, and there have been some reports (I think also in the sandbox, or possibly in the Stamps in Class forum) of some problems created on the PC side when measuring higher voltages. That's what Bean is referring to when he mentioned making sure you don't have any ground differential.


John R.
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02-20-2007, 01:24 AM
Yes.· I will be carefull of floating reference measurements.· Mostly everything I will be working with is grounded neutral source (residential) which is same gnd as PC & scope.· If there is ever a question I would use a differential probe.

This kind of brings me back to the original question of being able to use different probes.· The input impedance is standard so it seems like it would be compatible with the banana to BNC adapter.

Hopefully tech support will get back with me on this subject.

Chris Savage
02-20-2007, 10:17 AM

The probes use barrel connectors, not banana jacks/plugs. You would no doubt need to custom fabricate an adapter. Take care.

Chris Savage
Parallax Tech Support