Dirt cheap and simple scope-based component tester - curve tracer

[codeboy2k]

I've tried your curve tracer with my Iwatsu ss-5705 today, it didn't work as expected. Sorry for my n00b question - is it because CH1 and CH2 are completely out of phase? I try to locate an 'invert' switch on the scope, but couldn't see anything. Does it mean that I have to build an inversion circuit to use my scope as a curve tracer?

Make sure that you have both inputs DC coupled. That should take care of the problem. You can invert the Y axis by pulling the channel B position control out (it's labeled PULL INV).

Excellent point about DC coupling - and nice catch on the pull-inv function - I missed that in the photos.  Sounds like you've got him all sorted now.

When I first started out using a scope (... maybe 1972)... I used to think oh, I'm probing a DC signal, I better choose DC coupling. and for any AC signals, I always chose AC coupling.  I felt the scope would 'esplode if I ever got that messed up... then I learned what the AC/DC coupling button actually did

[george graves]

If you take a look at the "ACTracer FG" webpage

Thanks for the link - $100 is a bit more that I would care to drop.

I think I'll pick up a audio isolation transformer and see how it works with my FG - thanks for the tip on that.

So - will an electrolytic cap(before it it goes bang!...) will look like a big old "D" on the scope?

[w2aew]

When I first started out using a scope (... maybe 1972)... I used to think oh, I'm probing a DC signal, I better choose DC coupling. and for any AC signals, I always chose AC coupling.  I felt the scope would 'esplode if I ever got that messed up... then I learned what the AC/DC coupling button actually did

That's why I did a video on that a few months ago!

[w2aew]

So - will an electrolytic cap(before it it goes bang!...) will look like a big old "D" on the scope?

If you limit your current to <<1mA, there will be no "bang"

[icon]

Hi

Excellent video - you have a new fan! George Graves has already asked the first question that popped into my mind (about using a function generator) - looks like I need to do some shopping for transformers. The other question that occurred to me when I was this was - could you do something similar to produce a voltage/voltage curve such as Dave J is showing here (skip to 5min 40sec)[1]:



or is that produced in a completely different way?

Regards
John

[1] I can't seem to get the video to start at a specific time - I've tried &t=05m40s and  &start=340

[w2aew]

Hi

Excellent video - you have a new fan! George Graves has already asked the first question that popped into my mind (about using a function generator) - looks like I need to do some shopping for transformers. The other question that occurred to me when I was this was - could you do something similar to produce a voltage/voltage curve such as Dave J is showing here (skip to 5min 40sec)[1]:
or is that produced in a completely different way?

In the video I showed, the scope is actually showing voltage vs. voltage in the XY mode - it just so happens that the Y axis (the CH2 input) is probing directly across a fixed resistor, so the voltage is directly proportional to the current.  This is precisely what Dave is doing in his video (voltage across a resistor).  XY mode in the scope just plots the two signals against each other (usually Ch1 and Ch2).  So, in any circuit where you want to see the response of one voltage to another, simply put the scope in XY mode.

[Fraser]

George,

Reference the  ACTracerFG.....

I agree that the ACTracer-FG does not come under the 'Dirt Cheap' banner, but it is interesting to look at the design. The deigner originally used only an on-board signal source, but recently added the external Function Generator input. The PCB is well photographed, so it may be possible to work out how he has arranged the FG input without a transformer. I have meant to reverse engineer the basic circuit used but I haven't really got the motivation due to having the Huntron units.

Aurora

[0xdeadbeef]

Not exactly dirt cheap, but mobile

http://www.elv.de/output/controller.aspx?cid=74&detail=10&detail2=9502&flv=1&bereich=&marke=

[Fraser]

Here is an interesting variant with adjustable test conditions for the DUT

http://www.techlib.com/electronics/curvetrace.html

Aurora

[Fraser]

Awwwwww 0xdeadbeef, why'd you have to go and show me a portable I/V unit ..... I can't resist portable kit    Thank you for the link.

My German isn't great but I managed to muddle my way through the ELV purchase process and I now have an ELV KT100 Kit on it's way to me in the UK. I bought the kit as the PCB is pre-populated with the SMD components and I think I'll enjoy constructing the remaining parts of it. Thank heavens the GBP has recovered a little against the Euro 

A portable unit will be very usefull when I don't want to lug around a mains powered Huntron or dual channel CRO/DSO. I found the manual for the unit here:

http://www.techome.de/manuals/58758_Komponententester_KT100_UM.pdf

The quality looks OK and I like the fact that I will have a schematic.

Aurora

[0xdeadbeef]

Hey, just don't blame me if it sucks. The only user review says that it's working well but the LCD has little contrast even at the highest setting. Then again, maybe this can be tweaked a bit.

[w2aew]

Here is an interesting variant with adjustable test conditions for the DUT

http://www.techlib.com/electronics/curvetrace.html

Aurora

This is a decent, more flexible variant of the original octopus idea.  The only downside I see to this design is that the voltage across the current sense resistor adds to the DUT voltage, thus adding to the apparent DUT resistance.  Not a big deal, but is a difference.  It therefore also allows for a grounded test signal source, like a function generator.

[KD0CAC John]

Just to double check , some of the older analog scopes had the component test function / switch ?
Any chance the Rigol  DS1152E has that , I would guess in the menu somewhere if it does ?
And the curve tracer link , is that for scopes without the component test function ?
Just to confirm ?
Thanks

[w2aew]

Just to double check , some of the older analog scopes had the component test function / switch ?
Any chance the Rigol  DS1152E has that , I would guess in the menu somewhere if it does ?
And the curve tracer link , is that for scopes without the component test function ?
Just to confirm ?
Thanks

A small percentage of older analog scopes had this feature built in.  Most do not.  I don't think the Rigol has the feature.  Thus, the circuit shown in the video, or in the various links in this thread, or in a Google search for Octopus Component Tester:
https://www.google.com/search?sugexp=chrome,mod=19&sourceid=chrome&ie=UTF-8&q=octopus+component+tester
can be used with nearly any scope that has an XY mode (nearly all scope should have XY mode).

Confirmed?

[KD0CAC John]

Thanks
At least all of these accessories do not take up much space as some gear .

[Fraser]

0xdeadbeef,

Don't worry, I take responsibility for my own mistakes 

There are two reviews...one for the built unit and one for the kit. The kit review says: "Very good and functional testers. First class components"

No mention of display issues and anyway these displays are now so cheap that I would fit a better one if needed 

Having looked at the schematic I believe it to be a pretty decent design and IMHO better value for money than the ACTracer as I get the benefit of total portability. If you were to look at Huntrons prices for an LCD display Tracker you would be horrified !

I don't like to waste money but this looks a pretty decent risk to me 

Thanks again for pointing me towards ELV. I have purchased from them before but had no idea that they could supply this unit.

Aurora

[codeboy2k]

I've always liked this curve tracer kit that I found several years ago, I bookmarked it, so I remembered it when this thread popped up.

I don't own this one, but the author/developer has done a nice job and it's had good reviews.  Sadly, he's not selling it anymore.

http://fullnet.com/~tomg/gooteect.htm

It wasn't cheap at $779 for the kit and $1200 fully assembled, but it included an audio function generator and triple output power supply.

[Fraser]

The ELV K100 arrived today 

Initial impressions of the kit are very good indeed. Professionally packed and quality components used.

I attach the unpacking photos

Aurora

[PlainName]

The ELV K100 arrived today

How did this turn out? Worth the money or a dead loss?

[KD0CAC John]

Aurora , also waiting to see your finished kit ?
I just noticed that other posts 2 ago are dated june 16 2012 , is this thread that old of a fluke over the net ?

[Fraser]

Sadly serious illness has placed most of my projects on hold for the past 2 years.

I am eager to catch up with these projects now that my health is improving. This will be very high on my priority list but I am presently concentrating on repairing some thermal imaging cameras.

Thanks for resurrecting this thread. The reports from others who have built this unit has been favourable and the negative comments regarding screen contrast have been addressed by ELV which is good news. Its just a voltage setting.

Fraser

[PlainName]

Oh, sorry to nudge you when you are not up to dealing with this. But good news that your health is improving.

Ummm... if it would help at all, I would be happy for you to ship the kit to me and I would be willing to try it out for you 

[Fraser]

You have rekindled my interest in this project. I need a rest from squinting at tiny SMT devices in the thermal cameras, so this will be a good diversion. I will see if I get time over the next few days. Watch this space.

Fraser

[eman12]

Thanks Alan For the Video.

[Alexei.Polkhanov]

I wanted to get ID vs VGS (Drain current vs Gate to Source voltage) curve traced for several MOSFETS. I fugured that since all DMMs and Programmable power supplies have USB interface I can create curve tracer program on my PC. I wrote a program for MATLAB that sends commands to equipment and voila I have the trace at no additional cost if I don't count 2-3 hours of my time.

I think this method is much more flexible than using these special tracers unless they can be connected to computer to read raw data. If you have raw measurements you can add any imaginable plotting, scaling and post-processing very fast. What do I do with this plot on oscilloscope? Is it showing 3.4V pinch off voltage or 3.5V .... or something in between ?

Before that I was looking at component tester made by Peak Electronic Design. They have a "PRO" version that comes with plotting software: http://www.peakelec.co.uk/acatalog/dca75-dca-pro.html Then I realized that such device is limited to standard tests and more importantly it is limited by available battery power. I have to agree it probably saves a lot of time when you are going through your junk box.