Starter Scope

[nctnico]

IMHO the AD2 is a good buy for the educational price. Even if you get a benchtop oscilloscope at some point I'm sure there will be use for the AD2.

[Shadders]

Well Today I ordered what some call my Toy, It was the Analog Discovery 2, with the student pricing of save 37% and with another 10% off, it was a deal I couldn't pass up.

Hi,
I looked at the package - $299 with the BNC adapter board for 30MHz bandwidth. The thing against this for me was that you need a PC to run the device. I have a Picoscope which has gone faulty, first the channel A jfet, and now the other channel too - they are a dual jfet package for the front end.

The Picoscope has a maximum input voltage of +/- 20volts, and the Analog Discovery 2 has +/- 25volts. I think for the picoscope i inadvertently sampled a voltage greater than 20volts without the 10x on the scope lead, causing the channel A fault.

I am testing my amplifiers and they have a bench supply of +/- 30volts, so i do need a rugged scope. The Rigol and Siglent have higher voltage protection (so it seems from the datasheet), so for me, this will be my purchase - higher bandwidth, higher voltage, 4 channels which allows for the ability to couple with an AWG for bode plots etc. Also, again the PC requirement i thought was great, but it is a real pain to use if you main laptop is Linux etc., with a bench scope - it can go anywhere with immediate setup.

Regards,
Shadders.

[rstofer]

I am easily amused by a 10k resistor and a 0.1 ufd capacitor.

Arranged as a low pass filter, here is the schematic and  Bode' Plot.

We know that when Xc = 10k the capacitive reactance is equal to the resistance and this is the -3 dB point and the phase shift should be -45 degrees.

Xc = 1 / (2*PI*f*C)  => 10,000*2*PI*(0.1*10^-6) = 1/f = 0.0063 therefore f=159 Hz.  This is the -3dB point.  The plot is pretty close!  Remember, real parts have tolerances...

I have attached the plot and an LTspice schematic - just a drawing, it won't simulate as drawn.

Watch this space, I'll be adding more experiments with my favorite components.

.

[tggzzz]

The Picoscope has a maximum input voltage of +/- 20volts, and the Analog Discovery 2 has +/- 25volts. I think for the picoscope i inadvertently sampled a voltage greater than 20volts without the 10x on the scope lead, causing the channel A fault.

And that's why I don't like *1/*10 switchable probes; sooner or later the switch will be in the "other" position.

[rstofer]

Same exact circuit as above but this time we'll look at the Forced Response.  We hit the circuit with a squarewave and plot the voltage rise and fall curves.

The Time Constant, Tau, of an RC circuit:  Tau = R*C or, for this circuit, 10⁴*10^-7 = 10^-3 = 1ms
We also know that in 6*Tau seconds, the capacitor will reach 99.85% of full value.

The charging equation is Vout = Vin * (1-e^-(t/Tau))  For this example, we let t/Tau = 6 to display the entire charge and discharge interval.

For the signal frequency, we want the output high for 6*Tau and low for 6*Tau so 12ms.  f=1/0.012 = 83 Hz.  The waveform is offset such that the output plot goes from 0V up to 1V.

I put a cursor at 1ms (1 Tau) and the output is 65%.  It should be 63.2% so, given tolerances, close enough.

[rstofer]

Same circuit as above except:  Lift the 1- lead from Ground and connect it to the junction of the resistor and capacitor.  This shows the utility of differential inputs, nothing about Channel 1 is connected to ground.  What we do here is measure the voltage across the resistor to get the current waveform as the current flows through the resistor and capacitor.  This differential measurement feature of the AD2 is far better than the A-B approach required by most scopes.  Alas, it won't work if you use the BNC adapter with scope probes.  As long as you use the fly leads, differential measurements are available.

Bottom line:  We are measuring the voltage across the capacitor and the current through the capacitor simultaneously.

We hit the circuit with a 1 kHz sine wave with 0V offset and 500mV amplitude.

The plot shows the current waveform in Orange and the voltage waveform in Blue.  The cursors show the current leading the voltage by 90 degrees.  ELI the ICE man, the current (I) leads the voltage (E) in a capacitive (C) circuit.  What I wanted to show is the 90 degree phase shift and, since 1 kHz was a period of 1 ms, 90 degrees would be 1/4 of that period or 0.25 ms  (250 us)  Graphically, I get 245.5 us which is close enough.

That -90 degree phase shift is why we draw capacitive reactance negative on the 'j' axis, inductive reactance positive on the 'j' axis and resistance horizontally on the 'real' axis.  The vector sum of all these vectors is the impedance of the circuit which has both magnitude and phase.

These 3 experiments take just two components and I can spend an entire morning playing with just these 3 experiments.  I truly wish I had had something like this when I was in college.  Alas, the slide rule was king and the HP 35 didn't come out until the end of my Junior year.  I couldn't afford it anyway...

As I said above, I'm easily amused by two components.

 

[rstofer]

Just for giggles, I decided to plot the impedance of the 0.1 ufd capacitor used above.  I have the Impedance Adapter so it's pretty easy.  We expect the impedance to be around 10k Ohms at around 160 Hz (see above) and we get that value around 164 Hz, close enough.

I haven't spent much time with the adapter, I have no idea what it can do beyond the obvious.

https://store.digilentinc.com/impedance-analyzer-for-analog-discovery/

ETA:  It is not necessary to have the Impedance Adapter to use the Impedance feature.  The Help file shows wiring schemes that will work just as well.  One thing missing is automatic selection of the resistor.  The Adapter does this by magic, the stand-alone approach requires the  user to select a resistor from the table on the Help page.

[rstofer]

The Picoscope has a maximum input voltage of +/- 20volts, and the Analog Discovery 2 has +/- 25volts. I think for the picoscope i inadvertently sampled a voltage greater than 20volts without the 10x on the scope lead, causing the channel A fault.

And that's why I don't like *1/*10 switchable probes; sooner or later the switch will be in the "other" position.

The bare AD2 has very limited voltage range and it's worth making sure to only use flyleads on low voltage circuits, like those powered by the internal power supplies.  For "learning" circuits, it is seldom necessary to go outside of +-15V for op amps and even then, the signal is usually +-10V.

Beyond that level, the BNC adapter can be used with standard scope probes but as pointed out, 1x-10x may not be a good way to go.  It might be better to find a pair of 10x only.  My DS1054Z is rated for a maximum of 300V RMS so 1x may not be much of a problem but one of these days I'm going to buy those 10x only probes.  Edit:  I just ordered 2 of the 3904-2 probes from Probe Master - these are 10x only and will primarily be used with the AD2.

I also lose differential inputs when using the BNC adapter and this is a really big deal.

https://store.digilentinc.com/bnc-adapter-for-analog-discovery/

[tggzzz]

The Picoscope has a maximum input voltage of +/- 20volts, and the Analog Discovery 2 has +/- 25volts. I think for the picoscope i inadvertently sampled a voltage greater than 20volts without the 10x on the scope lead, causing the channel A fault.

And that's why I don't like *1/*10 switchable probes; sooner or later the switch will be in the "other" position.

The bare AD2 has very limited voltage range and it's worth making sure to only use flyleads on low voltage circuits, like those powered by the internal power supplies.  For "learning" circuits, it is seldom necessary to go outside of +-15V for op amps and even then, the signal is usually +-10V.

Beyond that level, the BNC adapter can be used with standard scope probes but as pointed out, 1x-10x may not be a good way to go.  It might be better to find a pair of 10x only.  My DS1054Z is rated for a maximum of 300V RMS so 1x may not be much of a problem but one of these days I'm going to buy those 10x only probes.  Edit:  I just ordered 2 of the 3904-2 probes from Probe Master - these are 10x only and will primarily be used with the AD2.

I also lose differential inputs when using the BNC adapter and this is a really big deal.

https://store.digilentinc.com/bnc-adapter-for-analog-discovery/

I agree with all that, and will confess to being a little jittery when I use a low-end USB scope on anything with more than, say +-12V around, or when I'm not completely sure of the potential to which I attach the probe shield.

[rstofer]

The Picoscope has a maximum input voltage of +/- 20volts, and the Analog Discovery 2 has +/- 25volts. I think for the picoscope i inadvertently sampled a voltage greater than 20volts without the 10x on the scope lead, causing the channel A fault.

And that's why I don't like *1/*10 switchable probes; sooner or later the switch will be in the "other" position.

The bare AD2 has very limited voltage range and it's worth making sure to only use flyleads on low voltage circuits, like those powered by the internal power supplies.  For "learning" circuits, it is seldom necessary to go outside of +-15V for op amps and even then, the signal is usually +-10V.

Beyond that level, the BNC adapter can be used with standard scope probes but as pointed out, 1x-10x may not be a good way to go.  It might be better to find a pair of 10x only.  My DS1054Z is rated for a maximum of 300V RMS so 1x may not be much of a problem but one of these days I'm going to buy those 10x only probes.  Edit:  I just ordered 2 of the 3904-2 probes from Probe Master - these are 10x only and will primarily be used with the AD2.

I also lose differential inputs when using the BNC adapter and this is a really big deal.

https://store.digilentinc.com/bnc-adapter-for-analog-discovery/

I agree with all that, and will confess to being a little jittery when I use a low-end USB scope on anything with more than, say +-12V around, or when I'm not completely sure of the potential to which I attach the probe shield.

One thing I often do is to connect my USB toys into a powered hub.  It's not total ground isolation but at least any load "oopsies" won't imapct the laptop.  I don't do SMPSs so I don't have a voltage problem but I could still go overcurrent.

Bottom line:  THINK!  Sketch out what you are doing if it is anythng above trivial and maybe even then.  See if you can sketch the grounds!  Include the scope grounds.

[Dellyjoe]

Well Today I ordered what some call my Toy, It was the Analog Discovery 2, with the student pricing of save 37% and with another 10% off, it was a deal I couldn't pass up.

Hi,
I looked at the package - $299 with the BNC adapter board for 30MHz bandwidth. The thing against this for me was that you need a PC to run the device. I have a Picoscope which has gone faulty, first the channel A jfet, and now the other channel too - they are a dual jfet package for the front end.

The Picoscope has a maximum input voltage of +/- 20volts, and the Analog Discovery 2 has +/- 25volts. I think for the picoscope i inadvertently sampled a voltage greater than 20volts without the 10x on the scope lead, causing the channel A fault.

I am testing my amplifiers and they have a bench supply of +/- 30volts, so i do need a rugged scope. The Rigol and Siglent have higher voltage protection (so it seems from the datasheet), so for me, this will be my purchase - higher bandwidth, higher voltage, 4 channels which allows for the ability to couple with an AWG for bode plots etc. Also, again the PC requirement i thought was great, but it is a real pain to use if you main laptop is Linux etc., with a bench scope - it can go anywhere with immediate setup.

Regards,
Shadders.

Shadders I got that package for 213 dollars, the AD2 is only 180 for the EDU price.

Just find a kid to buy it for you and give him 10 dollars.

Joe

[Dellyjoe]

The Picoscope has a maximum input voltage of +/- 20volts, and the Analog Discovery 2 has +/- 25volts. I think for the picoscope i inadvertently sampled a voltage greater than 20volts without the 10x on the scope lead, causing the channel A fault.

And that's why I don't like *1/*10 switchable probes; sooner or later the switch will be in the "other" position.

The bare AD2 has very limited voltage range and it's worth making sure to only use flyleads on low voltage circuits, like those powered by the internal power supplies.  For "learning" circuits, it is seldom necessary to go outside of +-15V for op amps and even then, the signal is usually +-10V.

Beyond that level, the BNC adapter can be used with standard scope probes but as pointed out, 1x-10x may not be a good way to go.  It might be better to find a pair of 10x only.  My DS1054Z is rated for a maximum of 300V RMS so 1x may not be much of a problem but one of these days I'm going to buy those 10x only probes.  Edit:  I just ordered 2 of the 3904-2 probes from Probe Master - these are 10x only and will primarily be used with the AD2.

I also lose differential inputs when using the BNC adapter and this is a really big deal.

https://store.digilentinc.com/bnc-adapter-for-analog-discovery/

What do you mean when you say I also lose differential inputs when using the BNC adapter and this is a really big deal.

[Dellyjoe]

The Picoscope has a maximum input voltage of +/- 20volts, and the Analog Discovery 2 has +/- 25volts. I think for the picoscope i inadvertently sampled a voltage greater than 20volts without the 10x on the scope lead, causing the channel A fault.

And that's why I don't like *1/*10 switchable probes; sooner or later the switch will be in the "other" position.

The bare AD2 has very limited voltage range and it's worth making sure to only use flyleads on low voltage circuits, like those powered by the internal power supplies.  For "learning" circuits, it is seldom necessary to go outside of +-15V for op amps and even then, the signal is usually +-10V.

Beyond that level, the BNC adapter can be used with standard scope probes but as pointed out, 1x-10x may not be a good way to go.  It might be better to find a pair of 10x only.  My DS1054Z is rated for a maximum of 300V RMS so 1x may not be much of a problem but one of these days I'm going to buy those 10x only probes.  Edit:  I just ordered 2 of the 3904-2 probes from Probe Master - these are 10x only and will primarily be used with the AD2.

I also lose differential inputs when using the BNC adapter and this is a really big deal.

https://store.digilentinc.com/bnc-adapter-for-analog-discovery/

I agree with all that, and will confess to being a little jittery when I use a low-end USB scope on anything with more than, say +-12V around, or when I'm not completely sure of the potential to which I attach the probe shield.

One thing I often do is to connect my USB toys into a powered hub.  It's not total ground isolation but at least any load "oopsies" won't imapct the laptop.  I don't do SMPSs so I don't have a voltage problem but I could still go overcurrent.

Bottom line:  THINK!  Sketch out what you are doing if it is anything above trivial and maybe even then.  See if you can sketch the grounds!  Include the scope grounds.

So you are saying I shouldn't use 1/10x probes, iss that b/c of the switch? and the other reason is b/c the AD2 is low voltage, so when probing lets say a 50v DC voltage I would need a 10x probe to bring the voltage down to 5v? which is then safe for the AD2

[rstofer]

So you are saying I shouldn't use 1/10x probes, iss that b/c of the switch? and the other reason is b/c the AD2 is low voltage, so when probing lets say a 50v DC voltage I would need a 10x probe to bring the voltage down to 5v? which is then safe for the AD2

I think the AD2 is pretty fragile compared to a normal scope (50V (probably peak to peak) vs 300V RMS and I would hate to lose mine due to a screw-up.  OTOH, I don't work with voltages outside of +-15V and, more often than not, I'm only working with the internal +-5V supplies.

Probes only come into play when you use the BNC Adapter so, most of the time, when using fly-leads, you need to be very careful.  I might just make it a practice that when not using the internal supplies, for whatever reason, use the BNC adapter and 10x probes.  Always!  That isn't much of a constraint considering you are using probes anyway.  Just use the right ones!

I bought a pair of the 3904-2 probes specifically for the AD2
https://probemaster.com/3900-series-scope-probes-100-mhz/

It all comes down to what you expect to do.  You could take a pair of 1x/10x probes and disable the switch (a wee bit of epoxy?) to prevent them from being set to 1x.

Protect that AD2!  You might also need to pay attention to the digital leads if you run into some awkward voltage level.  It seems unlikely but maybe it could be a problem.

If you don't know what voltage to expect, use a DMM first.

I really like the AD2 but it's expensive, I don't want to mess it up!

[Dellyjoe]

So you are saying I shouldn't use 1/10x probes, iss that b/c of the switch? and the other reason is b/c the AD2 is low voltage, so when probing lets say a 50v DC voltage I would need a 10x probe to bring the voltage down to 5v? which is then safe for the AD2

I think the AD2 is pretty fragile compared to a normal scope (50V (probably peak to peak) vs 300V RMS and I would hate to lose mine due to a screw-up.  OTOH, I don't work with voltages outside of +-15V and, more often than not, I'm only working with the internal +-5V supplies.

Probes only come into play when you use the BNC Adapter so, most of the time, when using fly-leads, you need to be very careful.  I might just make it a practice that when not using the internal supplies, for whatever reason, use the BNC adapter and 10x probes.  Always!  That isn't much of a constraint considering you are using probes anyway.  Just use the right ones!

I bought a pair of the 3904-2 probes specifically for the AD2
https://probemaster.com/3900-series-scope-probes-100-mhz/

It all comes down to what you expect to do.  You could take a pair of 1x/10x probes and disable the switch (a wee bit of epoxy?) to prevent them from being set to 1x.

Protect that AD2!  You might also need to pay attention to the digital leads if you run into some awkward voltage level.  It seems unlikely but maybe it could be a problem.

If you don't know what voltage to expect, use a DMM first.

I really like the AD2 but it's expensive, I don't want to mess it up!

ok so i did get the BNC adapter, and i brought two probes from there website I believe they are 1/10x, so i should be able to go up to 150VDC right? and atm the probes you have are a little out of my price range, maybe when the tax return comes in I can get that.

Joe

[TK]

I wouldn't try connecting anything high voltage on a scope that is connected to the laptop or PC through USB, and by high voltage I mean mains 120V or even 50V.  Laptops are not connected to ground.

[rstofer]

What do you mean when you say I also lose differential inputs when using the BNC adapter and this is a really big deal.

Due to code requirements, all non-current carrying metallic surfaces are to be tied to earth ground (or double insulated or some other limited exceptions).  That's why the barrel of the BNC connector is connected to earth ground through the power cord of a normal scope.  The same logic applies to the BNC adapter board, the barrel of the connector is connected to earth ground (when possible) through the USB cable and and on through the PC power supply.  Well, if one side of the scope channel is tied to ground, you can only take measurements relative to ground with the probe tip.  You can play math games and use 2 channels to get a differential reading but that's about it.

Having both sides of the scope channel float means I can measure the voltage drop across a component even if one end isn't grounded as in the current measurement I mentioned above.  Now, the AD2 voltage range is limited, that's true, but differential probes for a regular scope are PRICEY!

Differential measurements come up all the time and the fact that the AD2 can do them with no issues is a really big deal.

Here is a very popular video that explains the problem of grounded BNC connectors:

https://youtu.be/xaELqAo4kkQ

[Dellyjoe]

I wouldn't try connecting anything high voltage on a scope that is connected to the laptop or PC through USB, and by high voltage I mean mains 120V or even 50V.  Laptops are not connected to ground.

what if it is your computer desktop and or a laptop grounded?

[rstofer]

ok so i did get the BNC adapter, and i brought two probes from there website I believe they are 1/10x, so i should be able to go up to 150VDC right? and atm the probes you have are a little out of my price range, maybe when the tax return comes in I can get that.

Joe

Well, just epoxy the switch and call it a day!

I shudder at the thought of using the AD2 at those voltage levels.

I think the Impedance Adapter is worthwhile and the Breadboard Adapter is particularly useful.  It doesn't show in the picture but you do get a solderless breadboard with the PCB.

https://store.digilentinc.com/breadboard-adapter-for-analog-discovery/

Word to the wise:  When you stick the breadboard down, stay away from the connector so you don't obscure the silkscreen labels.  The breadboard will be outside the lines but I think not having the labels is pretty poor.  There's a reason I know this!

[rstofer]

I wouldn't try connecting anything high voltage on a scope that is connected to the laptop or PC through USB, and by high voltage I mean mains 120V or even 50V.  Laptops are not connected to ground.

what if it is your computer desktop and or a laptop grounded?

Watch Dave's video!  The probe ground is a nightmare in the making!  I emphasized the "learning" environment for the AD2 and I certainly wasn't thinking about voltages anywhere near 50V DC.  You can see where my experiments were run at 1V peak to peak.  I like low voltages!

[magicsmoke]

Well Today I ordered what some call my Toy, It was the Analog Discovery 2, with the student pricing of save 37% and with another 10% off, it was a deal I couldn't pass up.

How did you get the extra 10% discount?

[TK]

I wouldn't try connecting anything high voltage on a scope that is connected to the laptop or PC through USB, and by high voltage I mean mains 120V or even 50V.  Laptops are not connected to ground.

what if it is your computer desktop and or a laptop grounded?

I am not an expert on power supplies, I think laptop power supplies are switching and you have mains earth up to the brick, but I don't know if it continues to the laptop as many of them has barrel dc jack with only 2 pins...

[Caliaxy]

The NEW keysight DSOX1204G has 2Mpts and can do 200,000wfm/s and includes free serial decoding... these specs were changed starting March 1, 2020 but not advertised loudly by Keysight

Sorry, it might not be the best thread to ask this question but, since you brought it up, do you happen to know more about this?
Is Keysight selling an oscilloscope with twice the memory and free serial decoding under the same name and for the same price it sold before March 1st, 2020? Are the new features part of a firmware update or only meant for the "new" model sold to new customers?

[TK]

The NEW keysight DSOX1204G has 2Mpts and can do 200,000wfm/s and includes free serial decoding... these specs were changed starting March 1, 2020 but not advertised loudly by Keysight

Sorry, it might not be the best thread to ask this question but, since you brought it up, do you happen to know more about this?
Is Keysight selling an oscilloscope with twice the memory and free serial decoding under the same name and for the same price it sold before March 1st, 2020? Are the new features part of a firmware update or only meant for the "new" model sold to new customers?

https://www.eevblog.com/forum/testgear/new-keysight-dsox1200x-and-edux1052-scopes-with-extended-capabilities/msg2948718/#msg2948718

[Caliaxy]

Thanks, I had missed that.

Hmm... In short, it looks like Keysight offers the serial protocol decoder for free to the new buyers (through a firmware update), but not to the suckers customers who bought the scope before March 1st, who would have to pay a little extra $308 to get the same thing.

OP, there is something to be learned from this...