Test Equipment: Oscillocopes

[MarkE]

Thanks TK, guys .

Very educational this thread.
I have no much electro experience, so measuring principles are a pain in an ars for me. Some tutorial like yours TK are very helpful. There is not many of such on YouTube.
Tell me please, is there situation when you measure just with one probe-end connected- no ground connected and what does it actually show that way?

All voltage measurements are across two nodes.  When you connect just the probe tip to the circuit, the other side of the measurement is whatever potential the outside barrel of the scope input happens to be at.  It may bear very little relation to anything specific in the circuit you want to measure.  The probe cable itself is an antenna.

I know when I connect some coil just on main probe-no ground, it shows me around 50-60Vpp amplitudes of whatever it catch from the air.
If I good understand , the correct measurement are performed if you exactly match the impedance of the probe/scope?

That is never the case using the common high impedance passive probes that most folks use.  The idea there is for the probe to impose as little effect on the circuit under test as possible.

Would that my de-coupling 1pf cap work here in this case- ?  I guess it would as the ringing is the mater of the capacitance of the wire.

1pF is very small in the context of a passive oscilloscope probe.  The cable back to the scope has 50pF - 100pF of parasitic capacitance.  Another 1pF won't make much of a difference.

TK- just thinking to get this probe. What is your opinion?  http://www.ebay.com/itm/High-Voltage-5KV-5000V-300MHz-Oscilloscope-Scope-Passive-Clip-Probe-100X-P2300C/281598591049?_trksid=p2047675.c100005.m1851_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20131003132420%26meid%3Dfbc3c9e6d2d743809e66c027e2f7b290%26pid%3D100005%26rk%3D5%26rkt%3D6%26sd%3D301521247426&rt=nc  -this is what I do not understand- can my scope + this 5KV probe (100x)  withstand that 5KV voltage, or does my oscilloscope must also support some more higher voltage?

Thanks

That probe looks OK.  Here it is shipped from within the US:  http://www.ebay.com/itm/Brand-New-Oscilloscope-Clip-Probe-P2300C-300MHz-5000V-5KV-High-Voltage-100X-/120878612465?pt=LH_DefaultDomain_0&hash=item1c24ed3ff1

The probe divides the input voltage by 100:1.  5KV at the probe tip becomes 50V at the input to the oscilloscope.  If your oscilloscope handles +/-50V then you can use the probe with voltages up to 5kV with the caveat:  The 5kV must be the peak measured voltage.  The ground clip introduces ringing that increases the measured voltage.  If your oscilloscope only handles a smaller voltage like +/-20V then the peak measured voltage that you can safely probe is +/-2kV.

[TinselKoala]

Thanks TK, guys .

Very educational this thread.
I have no much electro experience, so measuring principles are a pain in an ars for me. Some tutorial like yours TK are very helpful. There is not many of such on YouTube.
Tell me please, is there situation when you measure just with one probe-end connected- no ground connected and what does it actually show that way? I know when I connect some coil just on main probe-no ground, it shows me around 50-60Vpp amplitudes of whatever it catch from the air.
If I good understand , the correct measurement are performed if you exactly match the impedance of the probe/scope?  Would that my de-coupling 1pf cap work here in this case- ?   I guess it would as the ringing is the mater of the capacitance of the wire.

TK- just thinking to get this probe. What is your opinion?  http://www.ebay.com/itm/High-Voltage-5KV-5000V-300MHz-Oscilloscope-Scope-Passive-Clip-Probe-100X-P2300C/281598591049?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20131003132420%26meid%3Dfbc3c9e6d2d743809e66c027e2f7b290%26pid%3D100005%26rk%3D5%26rkt%3D6%26sd%3D301521247426&rt=nc  -this is what I do not understand- can my scope + this 5KV probe (100x)  withstand that 5KV voltage, or does my oscilloscope must also support some more higher voltage?

Thanks

That looks like a probe you could actually use for real signals up to 5kV all right.

The probe attenuates the voltage to the scope's input. The scope's published input voltage limit assumes no attenuation, I think. So I think that if your scope says "400 volts" as the channel input limit, that means 400 V maximum actual signal with a 1x probe or direct connection. I THINK. I hope MarkE can give his input here.

Yes, the probe attenuation and the scope's channel input setting should match, otherwise the voltage readings will not be accurate. Yes, if your ground clip isn't connected to anything then you can pick up all kinds of crazy stuff, but sometimes the probe is adequately grounded anyway through the scope chassis and the mains power cord, so it can work in certain cases.

[Pirate88179]

Bill, doesn't your 2213 have the same kind of vertical range knobs and markings as the 2213a? The markings should be self-explanatory... if you use a 10x probe you read the value under the "10x probe" marking and that's what you get on the graticule.  See the image below for the switch markings...
My old HP180 does not have markings like this, so if I use a 1x probe setting, the switch marking is what I get on the graticule. If I use a 10x probe setting, I have to mentally multiply the switch marking by 10 to get the graticule value.  The probe gives you the voltage between the clip and the tip. That's why I call the ground clip the "reference" because it doesn't necessarily have to be at the "ground" of the circuit under test. (For most scopes the clip IS grounded to the mains ground though). All the probe references should be connected to the same point though, and if the circuit under test is actually grounded, this should be the connection point of the probe references as well, otherwise you set up a groundloop condition.  But with a battery powered, ungrounded circuit like a JT, you can connect the "ground" of the probe at whatever point you want to use as a reference for the tip voltage.

TK:

OK, now I feel even more stupid.  I just looked at my scope and....sure enough, there is a designation for 1x and 10x.  I never noticed that before.

Thank you so much.

Bill  (my face is still red)

[Brian516]

If you already have some programming experience but just not with c, or even if you don't, probably the best way to learn is just to look at example sketches and start changing them and see what happens. It's really pretty easy to do the basic stuff, the Arduino IDE comes with a lot of basic example sketches. Most people start with the "blink" sketch which just blinks an LED.  The Arduino online references are excellent and the programming interface is portable, runs on any computer OS, so you can write your sketches on a Mac, load them with Linux, run and display serial data on Windoze etc.

Here's a handy thing I made: 
http://www.youtube.com/watch?v=S6N8ys8FiA4

And just to steer back to the topic of oscilloscopes, here's a scoposcopy video showing how the Inductometer does its magic:
http://www.youtube.com/watch?v=Qx3B89379eQ

TK-
I have a little experience with HTML5 but that's about it, and it's been a few years since I've done anything with it. I need an LCD and I have plenty of them laying around from things I took apart, and it looks quite easy to mod one to use for the duino. I just need to find an instructional and i'll be good to go!  Then the first thing I am going to make is definitely that LC meter! I don't have an LCR meter. Definitely perfect timing on your part with posting that vid and info! haha  Thanks for that!

I went and picked up that scope today, and it certainly needs some TLC.  First of all, the only "working" probe it has is an original and it definitely has at the very least one short in it. feels like a break in the coax center wire, and there are a few spots where the sheathing is nicked and shielding exposed.  It sat in a workshop that doesn't have very good humidity control (a basement) for 9+ years, so when turning some of the knobs, the trace flickers. 
First thing I'm going to do before I do anything more than open it for a look is order at least one new probe and wait for that to get here so I can really see what else might be wrong.  Channel two does put a trace on the screen, but whatever is wrong with it is making it look like the trace is "driving" across the CRT at 100mph.  She's definitely getting a restore job....  gotta get a can of de-ox it and some IPA.  Found a thing off EEVblog of someone fully restoring the exact scope that I have, so that should help a little. Oh, and it came with the original service manual as well.  Got the GR 1330-A, and ended up with a 1000W kenwood excelon amp, too.
Anyone have any suggestions or references that may be helpful?

[edit]
I've got everything out here on the table, other than the scope itself.  I did a continuity test on the lead I used to check the scope while I was there, and it's shorted to the max. even the ground is somewhat shorted. That may have been the only thing causing the trace to go haywire on me, so I'm glad I took it regardless.  I have one lead connector/cable here that is in great condition, and it's for the probe I linked to below.  I have almost all the parts for it. What's missing is the little button for "GRD REF".  Is that going to be a problem?   The only real issue with rebuilding it is that I have to reuse a crimp connector piece, but I should be able to re-round it out after I drill out and pick out the remaining wire.
It says it is both 1X and 10X, so I guess that means all I would need to do is flip the switch on the probe lead itself to change..? and of course the setting on the scope, as well.
http://www.ebay.com/itm/TEKTRONIX-OSCILLOSCOPE-TEST-PROBE-10-X-MODEL-P6062A-/351289693035?pt=LH_DefaultDomain_0&hash=item51ca7f536b
( It is that one, but it is selectable between 1X and 10X.)

As for buying new leads, it would make sense to get a set of 4 (two 1X and two 10X) so I can match them on both channels, since I intend to fix channel 2, correct?
It sounds like I should also buy a 100X, 2kv to 5kv probe as well, if I can, right?  should I also try to get two of those?
How does that work using a 100X probe when the highest setting on the scope is 10X? Just use 10X setting and multiply all the readouts by 10?

I also would like a confirmation from someone about the 5kv probe and attenuation issue that TK spoke of in his last post. Wouldn't wanna go destroying a perfectly good vintage piece of equipment! haha

Thanks!
Brian

[TinselKoala]

TK-
I have a little experience with HTML5 but that's about it, and it's been a few years since I've done anything with it. I need an LCD and I have plenty of them laying around from things I took apart, and it looks quite easy to mod one to use for the duino. I just need to find an instructional and i'll be good to go!  Then the first thing I am going to make is definitely that LC meter! I don't have an LCR meter. Definitely perfect timing on your part with posting that vid and info! haha  Thanks for that!

You'll find plenty of tutorials for adapting certain surplus LCDs to the Arduino. The disadvantage is that they will need six or seven data lines to work, taking up output pins on the 'duino. That's why I like the Parallax brand serial LCDs, they only need one data line, and the two power leads, to give full functionality including the built in piezo speaker and backlight control.
I'm glad you find the Inductometer interesting! You can also make a capacitance meter with essentially the same circuit simply by using a known inductance instead of the known capacitance standard, and changing the sketch math a little bit. You don't actually need the LCD display; if you keep the Arduino plugged into your computer with the USB cable you can use the serial monitor in the Arduino IDE and put Serial.print statements in your sketch to give you the readout on your computer in real-time.

I went and picked up that scope today, and it certainly needs some TLC.  First of all, the only "working" probe it has is an original and it definitely has at the very least one short in it. feels like a break in the coax center wire, and there are a few spots where the sheathing is nicked and shielding exposed.  It sat in a workshop that doesn't have very good humidity control (a basement) for 9+ years, so when turning some of the knobs, the trace flickers. 
First thing I'm going to do before I do anything more than open it for a look is order at least one new probe and wait for that to get here so I can really see what else might be wrong. 

You can always use a direct connection with a patch cord from your signal generator to the scope channel. This will be equivalent to using a 1x probe. Strictly speaking I suppose you should use a 50 ohm impedance BNC patchcord with a T-fitting and a 50 ohm terminator at the scope input, but just a straight patchcord will work fine for low frequencies and casual testing.

Channel two does put a trace on the screen, but whatever is wrong with it is making it look like the trace is "driving" across the CRT at 100mph.  She's definitely getting a restore job....  gotta get a can of de-ox it and some IPA.  Found a thing off EEVblog of someone fully restoring the exact scope that I have, so that should help a little. Oh, and it came with the original service manual as well.

That's good, maybe it's just a trigger problem or even just dirty switch contacts. The fact that you get a trace at all on CH2 is really good news!

Got the GR 1330-A, and ended up with a 1000W kenwood excelon amp, too.
Anyone have any suggestions or references that may be helpful?

I love that old General Radio gear! There is nothing like it, their designers were truly geniuses in those days. I found a manual for your oscillator, attached below. It looks like it has those weird type 847 "bisexual" connectors,  you might like to look around for BNC adapters for those things. The tubes aren't too weird, you can probably find replacements on the market, although I haven't looked. Svetlana is a possible source for new tubes if you need them.

[edit]
I've got everything out here on the table, other than the scope itself.  I did a continuity test on the lead I used to check the scope while I was there, and it's shorted to the max. even the ground is somewhat shorted. That may have been the only thing causing the trace to go haywire on me, so I'm glad I took it regardless.  I have one lead connector/cable here that is in great condition, and it's for the probe I linked to below.  I have almost all the parts for it. What's missing is the little button for "GRD REF".  Is that going to be a problem?   The only real issue with rebuilding it is that I have to reuse a crimp connector piece, but I should be able to re-round it out after I drill out and pick out the remaining wire.
It says it is both 1X and 10X, so I guess that means all I would need to do is flip the switch on the probe lead itself to change..? and of course the setting on the scope, as well.
http://www.ebay.com/itm/TEKTRONIX-OSCILLOSCOPE-TEST-PROBE-10-X-MODEL-P6062A-/351289693035?pt=LH_DefaultDomain_0&hash=item51ca7f536b
( It is that one, but it is selectable between 1X and 10X.)

Those old Tek probes are fine but you might find them harder to repair than you think. I have a couple similar ones that I never use, they are just too clunky compared to modern probes.  Yes, the selection switch setting should match the scope's setting for attenuation. I don't know if the scope will autodetect that probe's setting or not, but you'll figure that out soon enough. ( Actually it should autodetect this probe, according to the spec sheet.) The missing GND REF button should not be a problem as long as it isn't stuck in "grounded" mode! I don't know if you have the spring clip tip adapter... this is almost a necessity so that you can clip the probe in place and then free up your hands. New probes will have clip adapters included with the kit.

As for buying new leads, it would make sense to get a set of 4 (two 1X and two 10X) so I can match them on both channels, since I intend to fix channel 2, correct?

Almost every modern probe you will find will have a 1x/10x switch so there is no need to buy separate probes for that. Pool your money and just buy 2 higher-quality probes for the price of 4 lower-quality ones.

It sounds like I should also buy a 100X, 2kv to 5kv probe as well, if I can, right?  should I also try to get two of those?
How does that work using a 100X probe when the highest setting on the scope is 10X? Just use 10X setting and multiply all the readouts by 10?

Yes, use the 10x setting on the scope and mentally multiply your graticule readings by 10. So the "20 v/div" range becomes 200 v/div with the 100x probe.
I can't imagine why you would actually need two high-bandwidth 5kV probes.... or at least I've only ever felt the need for one HV probe myself --- so I'd say  "it depends". If you do need a second one you can always get it when you need it.

I also would like a confirmation from someone about the 5kv probe and attenuation issue that TK spoke of in his last post. Wouldn't wanna go destroying a perfectly good vintage piece of equipment! haha

Thanks!
Brian

I think MarkE already said pretty much the same thing I said about the scope's input voltage limit and the probe attenuation; the input limit spec is raw, that is, not attenuated. So the 100x probe reduces the actual voltage from the signal by 100x at the scope's input jack. So if you have a 400 v input limit (as my Tek2213a does) then you are totally good to go with your 5 kV 100x probe because you'll reach the probe's limit far before you reach the scope's limit. 5 kV signal will mean only 50 V at the scope input, and a scope setting of 50 v/div (10x) will give you 500 v/div with the 100x probe and you'll run out of screen height before you hit either the probe or the scope limits. 

But you had better know what you are doing if you are really intending to work with voltages that high! You don't get to make many mistakes with voltages like that. Keep one hand in your pocket while working with those voltages so you don't accidentally take a shock across your chest.