Did I ruin my oscilloscope? - Page 1
Forum section: electronics / testgear

author: Rene
author_rank: Regular Contributor
timestamp: October 23, 2014, 09:44:10 pm
content: Hello everyone,I recently got my very first oscilloscope ever and it didn’t take long before I did something stupid (3 days to be exact). Attached is a depiction of how I connected my oscilloscope to my sample circuit.As you can see, I screwed up because I connected the negative alligator clips from Channel 1 and channel 2 to a voltage potential difference effectible creating a short-circuit. The good news is that the oscilloscope didn’t blow up nor did I see any smoke coming out of it.The reason I noticed that something was going on was because I saw my 5 volt supply current spike from 0.02 amps to 3 amps. Then after a couple of seconds I realized what the problem was and immediately disconnected the oscilloscope from my circuit.After I unplugged the oscilloscope, I connected both channels to the test square wave output used to adjust the probes and everything looked ok (according to me) but I am not sure if I did something to the oscilloscope that is not obvious at first sight.So do you guys think I ruined my brand spanking new oscilloscope?Thanks.

author: Thor-Arne
author_rank: Unknown
timestamp: October 23, 2014, 09:55:57 pm
content: I think it survived the ordeal.Go watchEEVblog #279, and then theOscilloscope training classthread.

author: grumpydoc
author_rank: Super Contributor
timestamp: October 23, 2014, 10:06:53 pm
content: The current will have gone through the probe leads shielding and 'scope chassis so the 'scope itself should be OK and 3A shouldn't have melted the probe leads. You probably got away with it.

author: pascal_sweden
author_rank: Super Contributor
timestamp: October 23, 2014, 10:09:52 pm
content: Are the negative sides of the 2 channels common to each other? Is this with all scopes?I thought that all scopes have 2 completely independent channels, meaning that the (-) sides are not common, neither the (+) sides. Or am I missing something here now? =)

author: EEVblog
author_rank: Unknown
timestamp: October 23, 2014, 10:10:13 pm
content: Almost certainly didn't break anything.All the current flowed through your BNC shield connectors on the front, and that would have been limited by the series resistor on top.Unless you are dealing with a massively high powered system, your scope will be fine.

author: EEVblog
author_rank: Unknown
timestamp: October 23, 2014, 10:11:14 pm
content: Quote from: pascal_sweden on October 23, 2014, 10:09:52 pmYes. You can measure this with your multimeter.QuoteNope!One of the biggest beginner mistakes.You need a special isolated input scope for that.

author: pascal_sweden
author_rank: Super Contributor
timestamp: October 23, 2014, 10:13:47 pm
content: Good to know! Really. I thought that anno 2014 everything is isolatedIs this also the same with Agilent and Tektronix?So beginners should buy this gadget from Siglent? =)http://www.siglent.eu/isolated-front-end.html

author: Fungus
author_rank: Super Contributor
timestamp: October 23, 2014, 10:19:08 pm
content: Quote from: EEVblog on October 23, 2014, 10:11:14 pmI would have imagined that as well. It's good to know.So... basically what happened is that he shorted out the bottom resistor through the BNC connectors.

author: Thor-Arne
author_rank: Unknown
timestamp: October 23, 2014, 10:19:51 pm
content: Quote from: pascal_sweden on October 23, 2014, 10:09:52 pmYes, the "negative sides" is common. In fact it's not part of the channels, it's connected to the scope ground as shielding for the signal beeing measured. And shouldalwaysbe connected to the same potential, usually the ground point of the DUT.If you need to probe on two sides of a part you need to use both probes on the part, with the probe ground connected to ground or another similar potential.You can also get a differential probe to achieve the same thing.

author: Thor-Arne
author_rank: Unknown
timestamp: October 23, 2014, 10:23:55 pm
content: Quote from: Fungus on October 23, 2014, 10:19:08 pmThe short went through bot probes ground clips, thru the shielding in the cable, to the BNC connected to the scope chassis.

author: tautech
author_rank: Super Contributor
timestamp: October 23, 2014, 10:27:27 pm
content: Quote from: pascal_sweden on October 23, 2014, 10:13:47 pmAs Dave said MOST scopes have commoned BNC grounds also with/to mains GND.The clip part of a scope probe should correctly be called the Reference lead, but everybody seems to refer to it as GND, presumably this reduces confusion.Not all are like this and one needs to know the difference.There are several current and older ISOLATED channel scopes available from most manufacturers.As for the Siglent ISFE, they have been on my interest list for a while and I will get one when I visit Siglent next week, and will start a thread on it for general interest/info.

author: pascal_sweden
author_rank: Super Contributor
timestamp: October 23, 2014, 10:27:46 pm
content: Quote from: Thor-Arne on October 23, 2014, 10:19:51 pmIf we take the original picture. You mean that he should have connected the probe of the second channel in the reverse order, so that (-) being common on the scope side, is also common in the circuit?How would a differential probe solve this, if we stick to the original picture, and keep the probes at the same location as was pointed out being erroneous. Would like to understand how the differential probe would solve this, and how it addresses that both (-) are common on the scope side and connected to ground.

author: Fungus
author_rank: Super Contributor
timestamp: October 23, 2014, 10:32:49 pm
content: Quote from: Thor-Arne on October 23, 2014, 10:23:55 pmI think that's what I said. More or less.From the information given we can also conclude that the top resistor is only 1.6 Ohms.

author: tautech
author_rank: Super Contributor
timestamp: October 23, 2014, 10:40:05 pm
content: Quote from: pascal_sweden on October 23, 2014, 10:27:46 pmThe simplist connection to a circuit when using 2 probes(for 2 waveforms) is to use only ONE reference(gnd) lead as in most scopes ALL reference leads are commoned.It will not matter where it connects to if the circuit is fed from a LV supply and in NO way referenced to Mains earth.When using 2 probes for differential measurements, use the Maths functions/options to obtain the differential between them. No refernce(gnd) required.

author: Thor-Arne
author_rank: Unknown
timestamp: October 23, 2014, 10:41:08 pm
content: Quote from: Thor-Arne on October 23, 2014, 10:19:51 pmQuote from: pascal_sweden link=topic=38044.msg535988#msg535988No. both ground clips at the lowest point.Then one can use the math function on the scope to get the The signals he wanted.The lower resistor, then the upper + the lower subtracted with the lower resistor.Quote from: pascal_sweden link=topic=38044.msg535988#msg535988The differential probe has two active tips, it displays the voltage between these. Not reference to ground.Edit: Too many quotes

author: Robyn
author_rank: Newbie
timestamp: October 23, 2014, 10:45:22 pm
content: Quote from: pascal_sweden on October 23, 2014, 10:27:46 pmThe BNC ground is connected to earth. If you measure an object that is grounded to earth as well you have connect it to ground of the object else you have a short too.

author: pascal_sweden
author_rank: Super Contributor
timestamp: October 23, 2014, 11:03:25 pm
content: My understanding of the scope inputs was that they are isolated, (-) independant from each other, and not even connected to ground. I was expecting that the scope measures the potential difference between (+) and (-). As it doesn't I will have to use a differential probe.Differential probe is just safest, and in fact easier to understand, as I just want to measure the potential difference. It's a shame scopes aren't designed like that by default. I believe they should if the connector is marked with (+) and (-). For power supplies you have this behaviour if the connectors are marked like that, and if there is a separate ground connector. So I expect the same from scope. But for now a differential probe will do, or the Siglent isolated front end adapter works fine too.

author: Thor-Arne
author_rank: Unknown
timestamp: October 23, 2014, 11:09:35 pm
content: The scope measures the signal between ground and the probe, the ground is common.You can still use two probes as a differential probe by using the math:subtract function.

author: pascal_sweden
author_rank: Super Contributor
timestamp: October 23, 2014, 11:10:50 pm
content: Quote from: tautech on October 23, 2014, 10:40:05 pmDo you mean that if you measure on both channels, and connect the probes with the BNC cable, that you actually just need to connect 1 ground (either from BNC cable 1, or from BNC cable 2)?Then you can make less mistakes right? Because the secondary channel (from which the tip is not connected) would get its reference from the main channel (from which the tip is connected)?So you need two probes, one with a tip and one without a tip

author: EEVblog
author_rank: Unknown
timestamp: October 23, 2014, 11:17:29 pm
content: Quote from: pascal_sweden on October 23, 2014, 10:13:47 pmHey, that's neat and fairly cheap, haven't seen that before.Beginners shouldn't just buy that, they shouldlearnthe limitations of their scope. That's why I did the video.

author: pascal_sweden
author_rank: Super Contributor
timestamp: October 23, 2014, 11:30:01 pm
content: Here is a stupid question: If you always have to connect the tip to ground, as your (-) at the scope side is connected to ground, why do you need the tip at all, as you are always measuring the potential difference between your signal and ground, and the scope is connected to ground already?I actually have seen once someone measuring with a scope, and he did not connect the tip. I found it rather funny, and was pointing out that he is measuring a potential difference, and therefore needs to connect both. But from the conclusions in this posting, my view on reality was wrong, as the scope seems to measure always referenced to ground. So now I am actually in doubt myself, and believe that the guy doing this measurement without tip, might not have been an idiot after all, or do I miss out something here =)

author: simingx
author_rank: Contributor
timestamp: October 24, 2014, 12:16:45 am
content: Quote from: pascal_sweden on October 23, 2014, 11:30:01 pmBecause the scope ground != your circuit ground.

author: pascal_sweden
author_rank: Super Contributor
timestamp: October 24, 2014, 12:20:18 am
content: Quote from: Robyn on October 23, 2014, 10:45:22 pmSo the above is not correct? Or you mean if the object is not grounded to earth, you need the tip, but if the object is grounded to earth, you don't need the tip? =)

author: simingx
author_rank: Contributor
timestamp: October 24, 2014, 12:37:58 am
content: Quote from: pascal_sweden on October 24, 2014, 12:20:18 amUnless you don't mind having a great big ground loop, you need to ground the scope as near to your measurement point as possible!

author: tautech
author_rank: Super Contributor
timestamp: October 24, 2014, 01:03:33 am
content: Quote from: pascal_sweden on October 23, 2014, 11:10:50 pmIf you have written TIP and mean CLIP as in Aligator clip (Ref, GND) then your understanding is correct.Remember ALL channel references (GND's) are at Mains ground potential.

author: tautech
author_rank: Super Contributor
timestamp: October 24, 2014, 01:13:50 am
content: Quote from: pascal_sweden on October 23, 2014, 11:03:25 pmIt's all about cost.In an Isolated channel scope, not only are the BNC shells isolated from Mains ground, also from each other.Scopes constructed in this manner are 4 Ch and often designed for use on 3 phase systems and therefore MUST have the appropriate CAT ratings as well.Non-isolated scope design elimimates much cost but presumes the user has the knowledge to use a scope safely.You also must refrain from thinking of signals in terms of + for probe and - for reference(GND).If you have a negative voltage signal then the reference(Gnd) is more positive with respect to the signal.Think probeTIPand ReferenceCLIP(Gnd)

author: vk6zgo
author_rank: Super Contributor
timestamp: October 24, 2014, 05:13:31 am
content: Quote from: pascal_sweden on October 23, 2014, 11:30:01 pmAstautechhas pointed out,you have your terminology backwards.The "tip" is the end of the probe which you attach to the point you wish to look at the voltage on,the "clip",or more correctly "earth clip"is the thing you attach to the "common" point of the circuit.Most equipment contains internal power supplies.Let us consider a device with +12v ,-12v,+5v,-5v supplies,all with one side of the supply connected to the common "rail".This "common rail"is connected to the chassis frame/cabinet .Forgetting the 'scope for a second,if you take a DMM,place its black lead on the chassis,& touch the red lead to the test points for the above supplies in succession,-----you will see +12v,-12v,etc.Let us assume that you have your 'scope sitting alongside this other device,all plugged in & ready to go.Now take your DMM & put the black lead on the outer part of the "scope's BNC connector.Check your voltage test points again.You will see:-+12v,-12v,etc!What has happened?This device,as is common in much non-domestic Electronic equipment not only returns one side of the power supplies to the chassis,but also connects the Mains safety Earth to the chassis.An experienced Tech,looking at the dc supplies in such a device,may set his "scope to "DC coupled" at,say,5v/div,'free run" the display,centre the line vertically on the screen,& touch the probe tip to the dc supply test points,so the horizontal line will deflect +2.4 large divisions for +12v,-2.4 for -12v,+ one large div for +5v,etc.Ideally,he would always attach the "earth clip" to the chassis/common rail,but for a quick check it is not unusual to rely upon the common connection via the Mains Earth system.It is normal practice when using a 'scope to measure everything with respect to the common rail,which in mains operated equipment is normally Earth/chassis.Measuring across a circuit with each side above Earth is seldom necessary,but can be achieved either using a purpose designed differential probe,or by the following method.Thinking back to our device with the multiple supplies,what if we wanted to measure the difference in voltage between the +12v & -12v supplies?(I mean look at the complete 24v)OK,we place both,(or only one--it doesn't matter) our "earth clips"on the common/rail/chassis(we shouldn't rely on the Mains Earth connection here,as it may introduce errors).Connect CH1 probe to one supply,CH2 to the other.You will,with 5v /div on each channel,see two lines 4.8 large divisions apart.Make one line the reference,& you will read off + or - 24 volts depending on which you chose.Perhaps the -ve & +ve lines need to be the same numerical value--you can then set the 'scope to "A+ B",& it will display the difference in that value.I would suggest you get a couple of "AA" batteries & have a play around in the "dc coupled" mode.

author: Andreas
author_rank: Super Contributor
timestamp: October 25, 2014, 07:02:05 am
content: Hello Rene,The things that you should test (with mains line disconnected from outlet).- is the minus line from CH1 connected to earth pin from mains (near zero ohms)- is the minus line from CH2 connected to earth pin from mains (near zero ohms)(in this case also CH1 and CH2 are still connected together)The connections have to be for security reasons because the minus lines can be touched by operator.(And you would not expect to have 110 or 230 V on the housing of the osciloscope):With best regardsAndreas

author: miguelvp
author_rank: Super Contributor
timestamp: October 25, 2014, 07:18:40 am
content: Using the ground clip to measure mains is a big NO NO. You'll be lucky if the only thing damaged is your scope.Ground is earth, not minus and not negative.Also it's AC so there is no minus. And even if English is not your language, minus means the same as in English and it's not ground/Earth.

author: tautech
author_rank: Super Contributor
timestamp: October 25, 2014, 07:32:50 am
content: Quote from: miguelvp on October 25, 2014, 07:18:40 am+1I can't beleive so many refer to scope inputs and probes in this manner.There is ONLY Signal input and it's Reference, commonly GND(but not always)No positive or negative inputs.... however the Signal might be positive or negative or BOTH and not AC.Where does this misunderstanding of scope inputs come from?DMM's?

author: idpromnut
author_rank: Unknown
timestamp: October 25, 2014, 12:29:40 pm
content: Quote from: miguelvp on October 25, 2014, 07:18:40 amI think Andreas was trying to say that the OP should check that the grounding on each channel is still working (i.e. with the scope not plugged into the wall, and checking the scope's mains ground pin against each channel's ground clip lead for low resistance).Doesn't invalidate your comment; be careful when you stick anything into the mains and know your equipment before doing so!

author: David Hess
author_rank: Super Contributor
timestamp: October 25, 2014, 02:01:25 pm
content: Quote from: EEVblog on October 23, 2014, 10:10:13 pmIt takes surprisingly low current to turn the micro-grabber style of probe ground lead white hot before melting it. I only had to make that mistake once and the oscilloscope was not harmed.

author: pascal_sweden
author_rank: Super Contributor
timestamp: October 25, 2014, 04:36:46 pm
content: Regarding the isolated front end option from Siglent:http://www.siglent.eu/isolated-front-end.htmlWhat is the deal with the bandwidth and peak to peak voltage?Does this mean that your scope does no longer measure the original signal with the original bandwidth provided by the scope and at the right voltage levels?I don't understand what they mean with 1 MHz bandwidth and 3 Vpp. Can someone explain this, as I plan to buy this to make sure I don't blow up my scope in the first week of usage

author: Nerull
author_rank: Frequent Contributor
timestamp: October 25, 2014, 05:34:39 pm
content: It has a 200:1 attenuation ratio - a 600V input signal is output as 3V. These things are meant for protecting your scope from high voltages.When measuring high speed signals, you have to consider how everything in the signal path effects the signal. Your scope has a maximum bandwidth rating, your probes have a maximum bandwidth rating, random pieces of coax have maximum bandwidth. This generally means that signals over a certain frequency are attenuated or distorted. This particular piece of equipment is rated for 1MHz. If you use it on anything higher than that you may not get good results, even if you hooked up to one of those 63GHz Agilent monsters. It's pretty rare to see high voltage and high frequencies together, and this thing isn't really intended for that.

author: pascal_sweden
author_rank: Super Contributor
timestamp: October 25, 2014, 05:51:40 pm
content: Okey, then I have to look for another device.I was planning to use this as an isolated front-end, to make sure that the clip on the probe is floating, and not connected to ground.I want to have a system where I can connect the probe tip and clip to any point in my electronic design, without any risk of making a short circuit. I want to make an objective measurement of the potential difference between the two measure points (the tip and the clip), without affecting the signals in my electronic design, and without affecting the functionality of my scope.If I understand well, this device from Siglent does it, but at same time provides attenuation, and limits the bandwidth to 1 MHz (at least does not affect signal characteristics below 1 MHz).What I am looking for is basically the same device, but without the attenuation and without affecting the bandwidth. Just the isolation of the input signals, to make sure that the clip of my probe can not cause a short circuit.Basically I am looking for an adapter (similar form factor as the Siglent adapter) which turns the standard Rigol probe (as delivered with the scope) into a differential probe, when I put it in between my scope and my probe. Does such an adapter exist?I want to use my standard Rigol probe as a differential probe, where I can connect the tip and the clip to any measure point without causing a short circuit. This should even apply when measuring with the 2 channels at the same time. I want that the clip of probe 1 is independant of the clip of probe 2.

author: tautech
author_rank: Super Contributor
timestamp: October 25, 2014, 06:08:00 pm
content: Quote from: pascal_sweden on October 25, 2014, 05:51:40 pmYou will have 4 options.Buy an isolated input DSO.Buy differential probes.Buy a 4 Ch scope and use std probes without Reference(Gnd) clips for a 2 Ch resultForget the idea and learn how to use a scope safely.

author: pascal_sweden
author_rank: Super Contributor
timestamp: October 25, 2014, 06:13:33 pm
content: Quote from: tautech on October 25, 2014, 06:08:00 pmRegarding the proposed options:Option 1) Not an option, I want to stick with MSO2072AOption 2) Where to get affordable/qualitative/reliable differential probe for MSO2072A?Option 3) Do you mean that you then will use the tips only and use math operations from the scope to combine tip1 and tip2 for the 1st channel, and tip3 and tip4 for the 2nd channel? Nice suggestion actually.Option 4) Even if you know what you are doing, you might make mistakes (e.g. on a Monday morning)

author: Marco
author_rank: Super Contributor
timestamp: October 25, 2014, 06:23:51 pm
content: Quote from: miguelvp on October 25, 2014, 07:18:40 amWhy? You might burn the ground clip I guess, but the rest of the path to ground should be chunky enough to survive till the fuse blows. The ground getting raised a bit shouldn't affect the circuitry either AFAICS.

author: tautech
author_rank: Super Contributor
timestamp: October 25, 2014, 06:29:21 pm
content: Quote from: Marco on October 25, 2014, 06:23:51 pmDepends on how big the fuse is.The current return path is via the GND tracks on the scope PCB.You can vaporize those tracks with enough current/energy..

author: Marco
author_rank: Super Contributor
timestamp: October 25, 2014, 07:07:11 pm
content: Quote from: tautech on October 25, 2014, 06:29:21 pmIsn't the BNC simply soldered to the ground plane, which is connected to the chassis at each standoff?

author: David Hess
author_rank: Super Contributor
timestamp: October 25, 2014, 07:28:28 pm
content: Quote from: Marco on October 25, 2014, 06:23:51 pmAs a concrete example consider when working on the primary side of a switching power supply with the ground clip connected to neural which is a bad idea but accept it now for the sake of argument. This creates a ground loop through the oscilloscope back to the distribution panel but the relatively high resistance of the ground lead connection limits the current compared to the return current through the neutral. Now if the neutral fails for whatever reason, *all* of the neutral current is going to go back through the oscilloscope ground and if the neutral failed because of a short, that could place the power line AC voltage across the oscilloscope from the probe ground to the earth ground.This is why I tend to use an isolation transformer even when using a differential probe.

author: David Hess
author_rank: Super Contributor
timestamp: October 25, 2014, 07:32:02 pm
content: Quote from: pascal_sweden on October 25, 2014, 06:13:33 pmPintek would be my first choice but I lack personal experience with their products.QuoteThis works in a pinch but lacks the common mode range and common mode rejection of a true differential probe limiting performance. Whether this is acceptable or not depends on the application. Some DSOs are unacceptably slow when operating like this.

author: RedOctobyr
author_rank: Contributor
timestamp: October 25, 2014, 09:15:44 pm
content: Please forgive my asking a question in someone else's thread, but it seems related to the discussion. If this is poor form, just tell meI'm new to all this, just got my first scope, and will watch/read the items linked in post #2.In the first post, Rene was measuring across 2 resistors.I'd like to measure the voltage drop across a current shunt (to figure out the current), with a 2 channel scope. So a similar situation, but just one resistor. The circuit is battery powered, so the scope and circuit both being grounded shouldn't be an issue.- I believe I could use the tip of the two channels, one before the shunt, one after. Then subtract one from the other to figure out the voltage drop across it. But using both channels feels like it might make things less accurate? At most, the drop across it should be 75mV, so fairly small.- As the circuit is battery powered, could I put the tip of channel 1 before the shunt, and the clip of channel 1 after it? Thereby measuring the voltage drop "directly" with a single channel? I wouldn't be able to use channel 2 for anything, I assume, as that might cause a reference voltage difference problem.Thank you.

author: Nerull
author_rank: Frequent Contributor
timestamp: October 25, 2014, 10:09:54 pm
content: Quote from: RedOctobyr on October 25, 2014, 09:15:44 pmThat sounds like the sort of job multimeters are designed for, but both methods will work fine. Beware that oscilloscopes are intended for accurate display of waveforms and not accurate reading of voltages and so their accuracy in this situation kind of sucks. It'll be close, but don't expect a better reading than a multimeter. The DS2072, for example, specs its DC gain accuracy at 2% full scale compared to 0.05% for a Fluke 87.

author: tautech
author_rank: Super Contributor
timestamp: October 25, 2014, 10:20:44 pm
content: Quote from: Marco on October 25, 2014, 07:07:11 pmI will not pretend to know the design or Gnd path PCB layout of all scopes available, but you just DO NOT expose your valuable test equipment to this type of abuse.

author: pascal_sweden
author_rank: Super Contributor
timestamp: October 25, 2014, 10:50:37 pm
content: Quote from: pascal_sweden on October 25, 2014, 06:13:33 pmI found the following differential probe on the Rigol Europe website:http://www.rigol.eu/products/accessories/rp1100d/Why is it so expensive? Are all differential probes in this price range?Is it because of the high voltage levels or because of the bandwidth?Does it really take 700 euro to make a non-isolated 100 MHz scope safer for short circuits?I don't need the protection for the high voltage, just the protection for short circuiting my probe in low voltage electronic designs (5V - 24V).Are there differential probes for lower voltage levels that are much cheaper?I need the bandwidth (at least 100 MHz), but not the high voltage range (just between 5V - 24V).

author: tautech
author_rank: Super Contributor
timestamp: October 25, 2014, 10:59:25 pm
content: Quote from: pascal_sweden on October 25, 2014, 06:13:33 pmWithout a dedicated Diferential probe you will only have 1 channel for use using this method from a 2 ch DSO.Thats why a 4 ch DSO is preferable....no additional cost for differential measurements using std probes. But you only can display 2 waveforms in this way.QuoteThen give up this hobby and find something safer to do.QuoteCAT ratings.No manufacturer can control how a user might use their equipment so all err on the side of safety.The Siglent ISFE is by far the cheapest option albeit at 1 MHz bandwidth which surpisingly will do most of ones work when this type of isolation is needed.BTW Siglent cheapest Differential probe:DPB3050 50MHz, + /?800Vp?p, error of 2%, 10X/100X attenuation ~US $485 RRP plus taxes if any.

author: RedOctobyr
author_rank: Contributor
timestamp: October 25, 2014, 11:28:11 pm
content: Quote from: Nerull on October 25, 2014, 10:09:54 pmThank you for the reply, I appreciate it.Sorry, I didn't mention that I'm looking to measure current spikes as servos start to move. So I'm looking to measure a very brief event, likely too quick for a multimeter to capture. But a scope should show it.My thought was to try putting a multimeter across the shunt, along with the scope, and flow a known, constant current through it. Letting me get some sense of "calibration" for the scope's reading, vs a multimeter. Not a perfect solution, but I'm trying to do the best I can with the tools I have access to.

author: tautech
author_rank: Super Contributor
timestamp: October 26, 2014, 01:01:43 am
content: Quote from: RedOctobyr on October 25, 2014, 11:28:11 pmFor precision measurements of this type one would use an oscilloscope Current probe.AC versions are passive units whereas DC units are powered active devices, neither are cheap.Owning a DSO is only the start, to use it to its full potential, one needs to acquire a collection of accesories.