Author Topic: Analog Discovery as a starter scope  (Read 2033 times)

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Offline tggzzz

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Re: Analog Discovery as a starter scope
« Reply #25 on: May 08, 2019, 06:17:51 pm »
I am thinking about buying an Analog Discovery 2 (with student discount).
...
P.S.:
- if you think this post is way off-topic pleas let me know, i will delete it if asked to do so
- i could get a Tektronix 465 as a gift (but analog scope + transient digital signals ...)

It is completely OT, but you may find other useful information in other threads in the forum.

A working Tek 465 is a delight to use, but as you note capturing one-off transients is the killer use-case for digitising scopes.

Be sure you understand the right type of probe to use for an application - they and your scope (and PC) become part of the equipment being tested. In appropriate types can damage the equipment you are testing, the scope, and you.

For your applications, be aware that the scope shield is tied to mains earth (via the PC in your case), so if you attach it to something that isn't at mains earth potential then either high currents may flow or the case could be at a dangerous voltage.
There are lies, damned lies, statistics - and ADC/DAC specs.
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Online exe

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Re: Analog Discovery as a starter scope
« Reply #26 on: May 08, 2019, 09:26:26 pm »
Yep, AD has a differential input, which is a huge advantage over other scopes. Basically, this makes it "foolproof": you can just put your probes anywhere* in the circuit and it will work.

*of course there are cases that is not true. Like, when using a bnc-adapter, or when voltage is outside of its range, or when probe loading is too high.
 

Offline tggzzz

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Re: Analog Discovery as a starter scope
« Reply #27 on: May 08, 2019, 10:10:51 pm »
Yep, AD has a differential input, which is a huge advantage over other scopes. Basically, this makes it "foolproof": you can just put your probes anywhere* in the circuit and it will work.

*of course there are cases that is not true. Like, when using a bnc-adapter, or when voltage is outside of its range, or when probe loading is too high.

A beginner has resurrected this thread, so it must be noted that is dangerously misleading to the point of being incorrect.

The AD has two earth-referenced inputs - the BNC's shields are connected together and to the protective mains earth via the PC.

You can subtract one input signal from the other, but in (the context of a scope) that is entirely different to having a differential input.
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".
Having fun doing more, with less
 

Offline grbk

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Re: Analog Discovery as a starter scope
« Reply #28 on: May 09, 2019, 12:42:39 am »
Yep, AD has a differential input, which is a huge advantage over other scopes. Basically, this makes it "foolproof": you can just put your probes anywhere* in the circuit and it will work.

*of course there are cases that is not true. Like, when using a bnc-adapter, or when voltage is outside of its range, or when probe loading is too high.

A beginner has resurrected this thread, so it must be noted that is dangerously misleading to the point of being incorrect.

The AD has two earth-referenced inputs - the BNC's shields are connected together and to the protective mains earth via the PC.

You can subtract one input signal from the other, but in (the context of a scope) that is entirely different to having a differential input.

What you say is true when using the BNC adapter board but is incorrect when using the AD without the BNC adapter board.

Without the BNC adapter board, the AD has "true" differential inputs, no scope math required. See the Analog Discovery manual, page 4, first paragraph: https://reference.digilentinc.com/_media/analog_discovery%3Aanalog_discovery_rm.pdf

The same is true for the AD2.

With the adapter board, the negative differential inputs are both tied to the BNC shields and earth (through the PC), which exe alluded to.

With that said, however, I would not describe using the inputs differentially as "foolproof" and I agree that the limitations and dangers should be explicitly stated, especially in a discussion with a beginner.
 

Online exe

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Re: Analog Discovery as a starter scope
« Reply #29 on: May 09, 2019, 03:24:33 am »
The AD has two earth-referenced inputs - the BNC's shields are connected together and to the protective mains earth via the PC.

I mentioned this in my answer.
 

Offline blue_Bandana

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Re: Analog Discovery as a starter scope
« Reply #30 on: May 10, 2019, 07:19:48 am »
Ordered an AD2 today, should be delivered tomorrow and the moment i completed the transaction i realized ... i need a Logic-Level-Converter ... Arduino 5V ... AD2 3.3V ... that's the kind of "i am afraid of missing something" i was talking about.

A TXS0108E based logic-level-converter should do the trick?

To set the record straight, i consider myself a newbie compared to the average scope-using eevblog user, i have been soldering the past ~10 years and repaired simple electronics for family and friends but i am not the "bins of ic's / gates etc in the cupboard" type, rather the "if a resistor or a big cap doesn't help let's put in an even bigger cap ... or plop in an arduino (even for the most basic logic things)"... i was always limited to the "multimeter-world". Only 1 short in 10 years  8).
Being able to solve differential equations in advanced physics in highschool and scoring 100% on every test didn't help me a bit, when circuits do not behave as ideal as "school theory", when every component starts to be a bit of everyting (L-C-R) and even changes behaviour with frequency ... i never had enough of a reason to get a scope but finally decided i don't need a reason to get one.
« Last Edit: May 10, 2019, 09:17:31 am by blue_Bandana »
 

Offline egonotto

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Re: Analog Discovery as a starter scope
« Reply #31 on: May 10, 2019, 09:53:58 am »
Hello

gratuliere zum neuen Gerät :) (congrats to the new AD2)


If you want use the Logic Analyzer inputs you dont need necessarily Logic-Level-Converter because :

"Input logic: LVCMOS (1.8V/3.3V, 5V tolerant)"

https://reference.digilentinc.com/reference/instrumentation/analog-discovery-2/reference-manual?redirect=1#refnotes:1:note1


Best regards
egonotto

PS: There is a good reference:
https://reference.digilentinc.com/reference/instrumentation/analog-discovery-2/reference-manual





« Last Edit: May 10, 2019, 10:13:54 am by egonotto »
 

Offline Fungus

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Re: Analog Discovery as a starter scope
« Reply #32 on: May 10, 2019, 05:41:15 pm »
Ordered an AD2 today, should be delivered tomorrow and the moment i completed the transaction i realized ... i need a Logic-Level-Converter ... Arduino 5V ... AD2 3.3V ... that's the kind of "i am afraid of missing something" i was talking about.

A TXS0108E based logic-level-converter should do the trick?

From the manual:

 

Online exe

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Re: Analog Discovery as a starter scope
« Reply #33 on: May 10, 2019, 06:35:23 pm »
"Input logic: LVCMOS (1.8V/3.3V, 5V tolerant)"

Yeah, this thing was made to survive students, I'd be very surprised if it was that easy to toast it :).
 
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Offline bitseeker

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Re: Analog Discovery as a starter scope
« Reply #34 on: May 11, 2019, 09:12:03 am »
The only worrisome part of the AD is the microUSB connector. It's rather common for one or more pins to break from its pads. Be mindful of the USB cable and all should be well.
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