Recommend me some scopes with differential inputs

[user 37518]

Can you guys recommend any scopes with differential inputs? im more interested on the older analog ones since I like them more for audio, but I've been on the hunt for a newer digital scope which can make calculations on-the-fly (when I say newer I actually mean a used one from the 90s  or early 00s because thats my budget) , something with 100Mhz or more Bandwith would be great.

Im more of a Tek guy but im open to suggestions.

Thanks!

 

[Andy Peters]

Can you guys recommend any scopes with differential inputs? im more interested on the older analog ones since I like them more for audio, but I've been on the hunt for a newer digital scope which can make calculations on-the-fly (when I say newer I actually mean a used one from the 90s  or early 00s because thats my budget) , something with 100Mhz or more Bandwith would be great.

Im more of a Tek guy but im open to suggestions.

The options for differential inputs are either use two standard inputs and let the 'scope manage subtracting the two, or to get a 'scope that supports a differential probe.

I was going to suggest something like the Tek DPO3054 I have on my desk at work, which will let you use a differential probe, but that kit will run you $15K.  But I'm here to testify: it's a great 'scope.

I just checked, and their DPO2024 for $3K supports the same differential probe as the 3054 but that probe is also as expensive as the 'scope. The thing is that these are all high-speed probes (500 MHz bandwidth), clearly above and beyond what you need for audio. But I don't know of any lower-bandwidth differential probes. Perhaps a third-party vendor makes them?

-a

 

[user 37518]

Thanks for the input Andy, yes those scopes are way off my budget. But now i want to ask you a dumb question, the differential probes that come with a power amp and psu can be used with any scope (alas a scope with no differential input) or i need a  scope which supports differential inputs? it seems to me at least that the power amp has the differential amplifier in it, and thus outputs the sum (or difference) of what the probe measured. Am i correct?

This is one example of the probe im talking about

 

[Samuel Groner]

What exactly are you trying to do, i.e. why do you need differential inputs? You can do basic differential measurements with about any scope by using two input channels and subtracting them.

A differential probe does just have a standard single-ended output, i.e. it can be used with any scope (as you can see in the pics you posted...).

Samuel

 

[bruno2000]

I bought a Tek 7000 series scope on eBay for $200, and 2 differential plug-in amplifiers for $50 each.  It's a mighty big 'scope, but it works great.

Examples:

http://www.ebay.com/itm/Tektronix-7A13-Differential-Comparator-Plug-In-for-Tektronix-7000-Series-Scopes-/300724215331?pt=LH_DefaultDomain_0&hash=item46048f5e23

http://www.ebay.com/itm/TEKTRONIX-7904-OSCILLOSCOPE-W-7A24-7A26-PLUGIN-SCOPE-MOBILE-202-1-CART-/350501369795?pt=BI_Oscilloscopes&hash=item519b8277c3

Disclaimer:  I have NOTHING to do with these listings.  They are for example ONLY.

Best,
Bruno2000

 

[user 37518]

What exactly are you trying to do, i.e. why do you need differential inputs? You can do basic differential measurements with about any scope by using two input channels and subtracting them.

A differential probe does just have a standard single-ended output, i.e. it can be used with any scope (as you can see in the pics you posted...).

Samuel

Hey Samuel, thats how ive been doing it so far taking my 2 probes and use the CHA-CHB mode.  I want to be able to safely measure floating voltages (aka SMPS) or say across a component, aswell as balanced circuits. I've reading a document published by Tektronix on differential probe measurements and such, and it seems that when measuring floating voltages or differential systems, the best way to get a true reading is with a differential probe, even if using 2 channels yield a very similar result.

I bought a Tek 7000 series scope on eBay for $200, and 2 differential plug-in amplifiers for $50 each.  It's a mighty big 'scope, but it works great.

Examples:

http://www.ebay.com/itm/Tektronix-7A13-Differential-Comparator-Plug-In-for-Tektronix-7000-Series-Scopes-/300724215331?pt=LH_DefaultDomain_0&hash=item46048f5e23

http://www.ebay.com/itm/TEKTRONIX-7904-OSCILLOSCOPE-W-7A24-7A26-PLUGIN-SCOPE-MOBILE-202-1-CART-/350501369795?pt=BI_Oscilloscopes&hash=item519b8277c3

Disclaimer:  I have NOTHING to do with these listings.  They are for example ONLY.

Best,
Bruno2000

Hey Bruno, thanks for the links, thats one big monster!!! ill look into it

 

[Samuel Groner]

Thats one big monster!

I second the Tektronix 7000 series. I think for low frequency/audio work the 7A22 is even better than the 7A13, as it has uV sensitivity, higher CMRR and adjustable bandwidth limiting filters. Also check for a 7603 mainframe, this one is smaller than the four-compartment ones.

I want to be able to safely measure floating voltages (aka SMPS) or say across a component.

For high common-mode voltages you need isolated probes, e.g. Tektronix A6902.

Samuel

 

[user 37518]

I want to be able to safely measure floating voltages (aka SMPS) or say across a component.

For high common-mode voltages you need isolated probes, e.g. Tektronix A6902.

Samuel
[/quote]

Samuel, is that needed even if im using an isolation transformer on the SMPS? , im guessing that the isolated probes, isolate the scope's ground from the device being measured, so the device being measured doesnt ground through the scope, am i right?

Thanks again!

 

[Samuel Groner]

Samuel, is that needed even if im using an isolation transformer on the SMPS?

I think you can indeed get around isolated probes with an isolation transformer, but I'm definitely no expert here.

Samuel

 

[bruno2000]

Thats one big monster!

I second the Tektronix 7000 series. I think for low frequency/audio work the 7A22 is even better than the 7A13, as it has uV sensitivity, higher CMRR and adjustable bandwidth limiting filters. Also check for a 7603 mainframe, this one is smaller than the four-compartment ones.

+1 for the 7A22.  That's what I have in my box.  Just couldn't find one on eBay to post.
There's also the smaller 5000 series.  There is a diff amp for that series, but I don't know much about it.  There was a shop in town giving away 5000 series frames.
Best,
Bruno2000