Atlas dca model:DCA55 any good? - Page 1
Forum section: electronics / testgear

author: carbon dude oxide
author_rank: Frequent Contributor
timestamp: June 02, 2013, 03:01:55 pm
content: Hello, where i work we sell an atlas DCA55 (semiconductor componant tester) and i would like to know if its any good. I have tried it a few times at debuging a couple of customers products, such as some broken triacs but is it work getting one?

author: alank2
author_rank: Super Contributor
timestamp: June 02, 2013, 03:06:25 pm
content: I've had one for a couple of years and I find it handy to use from time to time. No problems with it.

author: lemon
author_rank: Frequent Contributor
timestamp: June 02, 2013, 03:14:47 pm
content: Very usefull tester.Look and DCA Pro, too! The curve tracer function is very good.

author: carbon dude oxide
author_rank: Frequent Contributor
timestamp: June 02, 2013, 03:25:11 pm
content: Ok thanks

author: carbon dude oxide
author_rank: Frequent Contributor
timestamp: June 02, 2013, 03:48:33 pm
content: I can get the pro for £87 where i work ^.^ is that a good price?

author: lemon
author_rank: Frequent Contributor
timestamp: June 02, 2013, 06:15:26 pm
content: Yes, it has £115.95 inc VAThttp://www.peakelec.co.uk/acatalog/dca75-dca-pro.html

author: Tube_Dude
author_rank: Regular Contributor
timestamp: June 03, 2013, 03:33:43 pm
content: I have one DCA55 and love it. No more need for checking in the data sheet the pinout of any transístor...

author: FlyNN
author_rank: Newbie
timestamp: June 03, 2013, 06:56:47 pm
content: I've had one for a few months and am pleased with its operation. A good piece of test equipment to have on the bench.

author: PA4TIM
author_rank: Super Contributor
timestamp: June 03, 2013, 07:59:30 pm
content: I got one too.Pro:- Very handy to check pins from transistors.- small- works 99% of the time wellDownside:- unusual 12V battery.- hFE measurement is more an indication.- Do not trust it blind. I have seen strange things and a friend too. Like a bad transistor he called a fet . Also two times a bad transistor that was stated good (i have a Tek 576 curvetracer, a Tek R Transistor timing plugin and a bunch of transistor testers)-very flimsy testleads and clips/- small (to much gear in my lab so I loose it)

author: Psi
author_rank: Super Contributor
timestamp: June 04, 2013, 12:42:46 am
content: I have one too and am very happy with it.But yeah, look at the pro version, its got more features that maybe worth getting.

author: PeakAtlas
author_rank: Contributor
timestamp: July 04, 2013, 12:28:48 pm
content: Dear All,I've just joined, so apologies if I've missed stuff. please point me in the right direction if anyone thinks I should be aware of something!Anyway, pleasure meeting you all on here and I hope I can make the odd useful contribution.You probably already know that Peak Electronic Design Ltd is a fairly small company in the UK, but that doesn't mean we don't try really hard to make things as good as possibleBeing little, we can be flexible and even make changes based on customer feedback fairly quickly, so if anyone has any suggestions, complaints (be gentle!) or anything else to say then I'd be delighted to hear.On that subject, PA4TIM mentioned a few points that I may be able to help with. We changed the test leads and test clips about 3 years ago to a much sturdier set that is still universal enough for most parts but much stronger that the old type. Drop me a line if you think you've got the old type (new variety is picture attached). PA4TIM also mentioned the odd battery type. Yes, I agree, the 12V battery is fairly unusual (compared to AA and AAA for example), but are still fairly easy to get hold of from auto shops or electronics shops. The duracell equivalent is MN21. They're available from us directly too if you're stuck.Anyway, enough waffle for my first post. Don't hesitate to prod me if there is anything I can help with.All the best,Jez Siddons

author: ddavidebor
author_rank: Super Contributor
timestamp: July 04, 2013, 01:42:48 pm
content: 12v battery is pre dc-dc converter stuff.I suppose in a few year (alredy is difficult to find) it will be anywhere. No one shop will sell it.First suggestion, redesign the power supply. With all the dcdc goodness from mobile phone tecnology, there is no reason to use an absolete battery.It's design lazyness from my point of view.

author: alank2
author_rank: Super Contributor
timestamp: July 04, 2013, 02:09:38 pm
content: Hi PeakAtlas,I've got a couple of your products and they are quite handy. I especially like the delay before scanning feature so you don't have to have a third hand on one of them.Thanks,Alan

author: PeakAtlas
author_rank: Contributor
timestamp: July 04, 2013, 02:24:33 pm
content: Hi David, thank you for your comment.The MN21 style battery does indeed have a long heritage and is still fairly popular in remote key-fobs, wireless doorbells, wireless alarm nodes, some photographic gadgets as well as some bits and bobs (such as some of our analysers). I agree entirely that it isn't the easiest battery to find, but there are many manufacturers out there that make it (see attached). I suspect that the big electronic distributors will supply them for many years to come. I've even seen them in my local stationers (WH Smith in the UK).In terms of design choices, it is horses for courses really. It does have the very notable feature of being very small and much more cost effective than coin cells for the user. in terms of size, the 12v battery is 50% the volume of an AAA cell. Additionally, the current consumption of the DCA55 is below 5mA most of the time while switched on. Using a switching PSU design for a low current consumption application is surprisingly power inefficient. Most switching PSU designs run at good efficiencies for currents above several 10's of mA. Hence their use in mobile phone type applications as you point out.Furthermore, for devices that are measuring fairly small parameters, switching power supplies can be pretty noisy and often have to be followed by a linear LDO to remove the noise completely (filtering is not always as effective as you need). Our Atlas SCR and Atlas DCA Pro products use a switchmode with a post-regulation of a linear LDO (they both use a single AAA cell). The consumption of both of those instruments however is much higher than 5mA and so the efficiency of the switchmode approach becomes sensible. Additionally, they are higher value products and can better stand the cost of the switchmode parts.So for our products that do have a very low current consumption, we find the use of a linear LDO offers a good combination of clean supply and good battery life (battery can go from 12V to 7V and stilll be operational).I can't pretend our designs are perfect, but I don't think we've been lazy in our design choices, more a case of applying the most appropriate parts for the application. We will always consider the availability of consumables in our design choices too.Best regards,Jez

author: PeakAtlas
author_rank: Contributor
timestamp: July 04, 2013, 02:33:33 pm
content: Hi Alan,Thanks for your message, much appreciated. Delighted that you like your instruments.Cheers,Jez

author: Unknown
author_rank: Unknown
timestamp: July 04, 2013, 03:29:02 pm
content: I bought a DCA55 recently and I'm pretty happy with it; I also like the fact they are based not too far away - just in case I drop it into my coffee by accident ;-)

author: PA4TIM
author_rank: Super Contributor
timestamp: July 04, 2013, 04:02:57 pm
content: Jez, mine is indeed older as 3 years. I noticed the later ESR 70 also had other leads. Idid not buy them but got them from a friend who had them surplus. So no clue about the age.http://www.pa4tim.nl/?p=3319I solved the leads problem like you see in the link above. They aways got lost in between tools and gear so I put them in a cabinet with mains supply.I realy like the component tester and I use it often. However for serious testing while designing or repairing I most times a use a Tek 576 curvetracer.I took a 3 pin din-socket and pins from an IC socket. I presolderd the pins, and the inside of the socket, heated the pins from the socket and pushed the IC pins in. This is much more easy for testing.Besides that I have mounted 3 banana sockets and I can plug my own clips in there.The ESR 60 is also good, I have done a lot of ESR measurements and this little thing is rather accurate and realy measures ESR instead of impedance. The C function of the 60 and 70 is not good when caps are bad, so just in the situation you need the ESR meter.I have done a lot of tests on bad caps using everything from impedance and LCR bridges to network analysers. The problem with bad caps ( DC leakage, loss of capacitance and high ESR) is that the C measurement using DC totaly goes wrong, the ESR and/or leakage is the cause of this.In a new test a few weeks ago using the 60 and the 70 and some Multimeters, they all went wrong. You find that test on my site ( in english, measuring ESR on bad caps)But sorry to say, in my opinion the LCR meter ( but I have an old version) is a disaster. For electrolityc caps it used DC again, under 10 pF ( or RF work conponents) it is not good either, but for allround LCR measure gismo to check if you got the good ceramic cap, or the value of a not RF coil, a resistor it is OK. The auto measurement is handy but not allways. Like this afternoon I was doing some tests on inductors and my IET DE-5000 thought I had a resistor (it was a GR 50-100 mH inductor) but in that case can switch off auto and choose a mode.On all I do not like the auto power of. I understand it because the battery life. But it is not handy, picture a multimeter where you have to do this each measurement. It would drive me crazy.Hope you see this as positive points, i do not mean to talk your stuff down. Just the opposite. I get many questions about sopes, multimeters, LCR and VNAs and several people bought the ESR meter after my advise.

author: PeakAtlas
author_rank: Contributor
timestamp: July 04, 2013, 04:21:14 pm
content: Hi PA4TIM,Many thanks for your comments, they are much appreciated and very useful to us. I will see what we can do to improve things in the areas you mention.By the way, we have extended the on-time of our ESR60/70 in recent years as we have been able to implement improved power management software that has been possible with more recent micros.I've seen your images, I've never seen anyone do that before with multiple units, that is very interesting.Kindest regards,Jez

author: Owen
author_rank: Contributor
timestamp: July 05, 2013, 08:10:15 am
content: Quote from: PA4TIM on July 04, 2013, 04:02:57 pmGreat tests! I like it. But which Peak ESR would you recommend? In practical: Is there any advantage over the 60 model? Would you recommend these or would recommend the a "real" LCR meter with ESR function?

author: Salas
author_rank: Frequent Contributor
timestamp: July 05, 2013, 08:31:19 am
content: Quote from: PeakAtlas on July 04, 2013, 02:24:33 pmHiWhat is the consumption for DCA Pro? Does it absolutely stop drawing from battery when connected to PC?

author: PeakAtlas
author_rank: Contributor
timestamp: July 05, 2013, 08:52:43 am
content: Quote from: Owen on July 05, 2013, 08:10:15 amThe *main* advantage of the ESR70 over the ESR60 is the audible feedback tones. The ESR70 generates little "bell-like" tones to indicate various thresholds of measured ESR. It also does a "beep-barp" when it detects a very high ESR. This allows you to bob along various capacitors in turn, listen for the tones and you know when you've got good, medium or bad ESR just from the nice tones.The ESR70 does also have double the ESR measurement range (40 Ohms instead of 20 Ohms) although it is rare that you're interested in the actual value of ESR if it's above 20 Ohms anyway, it's a pretty poor capacitor that would have an ESR of 20+ ohms.Both the ESR60 and ESR70 have an automatic controlled discharge function so are better protected against charged caps compared to some LCR/ESR meters out there. They don't just clamp the probes with a pair of diodes, they perform a highly controlled "constant power" discharge until the voltage is sufficiently low so that it can then proceed to do an ESR measurement.Both the ESR60 and ESR70 have the same measurement resolution of 0.01 Ohms and this is measured at the "industry standard" of 100kHz that most capacitor manufacturers like to specify.The capacitance measurement function is a secondary measurement for the ESR60 and ESR70. It's main task is to measure ESR (which it can do in-circuit in most cases). Capacitance is generally measured if the capacitor is out-of-circuit but can be handy as an additional confidence indicator of a capacitor's condition.Cheers,Jez

author: PeakAtlas
author_rank: Contributor
timestamp: July 05, 2013, 09:00:21 am
content: Quote from: Salas on July 05, 2013, 08:31:19 amThe DCA Pro doesn't draw any current from it's AAA cell when it's connected to a powered-up PC. In fact, you don't need a battery in it at all when you're connected to the PC.Cheers,Jez

author: Salas
author_rank: Frequent Contributor
timestamp: July 05, 2013, 09:05:23 am
content: Why the DCA Pro changes VDS when testing various types JFETs IDSS? It would be nice if it could stay put so the readings can be comparable. Like 10V VDS for instance. Also what is the accuracy for HFE tests?

author: PeakAtlas
author_rank: Contributor
timestamp: July 05, 2013, 09:25:42 am
content: Quote from: Salas on July 05, 2013, 09:05:23 amHi,I will investigate your question about the VDSwhen testing JFETs. I do know that the DCA Pro (in stand alone mode) attempts to use a constant current of 5mA for the IDS, although that can be lower if the JFET has a lower saturation current than that. Like I say, I'll investigate the VDSquestion a little further and answer you properly.In PC mode, you have much greater flexibility on the test conditions for measuring various parameters. The parameters are automatically populated when you first do a fresh component analysis but you can still choose your own. You can even export your data to Excel or Open Office if you want to calculate some further parameters (such slope resistances etc).In answer to your HFEaccuracy question, the HFEis measured to an accuracy of nominally ±3%.I hope that helps,Jez

author: Salas
author_rank: Frequent Contributor
timestamp: July 05, 2013, 11:07:30 am
content: Thanks for the accuracy spec. Whenever IDSS is >5mA it shortens VDS. I think that it would be useful to keep that parameter steady and independent.

author: PeakAtlas
author_rank: Contributor
timestamp: July 05, 2013, 11:15:30 am
content: Quote from: Salas on July 05, 2013, 11:07:30 amI agree, I think that would make a nice enhancement. I'll discuss with my esteemed colleagues here. Thank you for your feedback.Cheers,Jez

author: Salas
author_rank: Frequent Contributor
timestamp: July 05, 2013, 11:20:43 am
content: Thanks for taking it to consideration. Examples even when on PC, attached. Data line of interest is bottom left for those unfamiliar.

author: PeakAtlas
author_rank: Contributor
timestamp: July 05, 2013, 11:43:47 am
content: Thanks for the screenshots. Am I right in saying that you'd like Vds to be a constant figure for the test when Vgs=0? That would yield a variable IDS that would change from part to part, is that what you'd like to be able to see to compare parts? I'm sure we could do that. Although there are some JFETS that want to sinklotsof current for a VGS of 0 for even tiny VDS values.By the way, you could perform a ID/VDS plot of your JFET with VGS set to 0 (or any other value for that matter). You can plot the same graph for any JFET you like and then compare them on the same graph (see attachment that I did for 3 samples of a 2SK170 audio JFET).Cheers,Jez

author: Salas
author_rank: Frequent Contributor
timestamp: July 05, 2013, 11:58:18 am
content: Yes. Id when Vgs=0 at a steady Vds value is the definition of Idss. Fundamental in characterizing and matching JFETs.Vds is 10 or 15V specified in most datasheets. 10V is a good compromise even for high Idss JFETs I have seen. They tend to become only marginally stronger CCSs above 10V.I am aware that I can go in tracer mode and set some parameters, but such a method is time consuming for when searching for matches through a batch. Identify mode with steady Vds option would be as quick as when matching HFE for BJTs.

author: PeakAtlas
author_rank: Contributor
timestamp: July 05, 2013, 12:00:56 pm
content: OK, leave that with us, we'll see what we can do.Thanks once again for your feedback,Jez

author: PA4TIM
author_rank: Super Contributor
timestamp: July 05, 2013, 12:10:40 pm
content: Quote from: PeakAtlas on July 05, 2013, 09:25:42 amJust for the record, it ishFEandhfe, just two of the many " h" or hybrid parameters that excist.The first is the DC amplification of a common emitter amplifier (F=forward, E= common emitter, capitals is DC ) and I think this is what the peak measures. The other one is the result of delta Ic to delta Ib, sometimes called small signal amplification. At DC the amplification can be 100 but at some frequeny, called Ft, the gain is dropped to 1 so if your peak shows you a gain of 100, this will not say this transistor has still a gain of 100 in your application at 10 MHz. But Datasheets show it so it is just a test. I have seen transistors with a perfect gain at a steady Ib, but an increase of Ib did not give a single reaction. This was while repairing an old HP. The Peak and some transistor testers told me it was good. The scope told me there was a problem. The Tek curvetracer showed me the real problem. But these are exeptions, just to tell you, never trust any instrument without thinking or cross checking.hfeis a bit more difficult to measure.From the wiki:https://en.wikipedia.org/wiki/Bipolar_junction_transistor#h-parameter_modelEtymology of hFEThe 'h' refers to its being an h-parameter, a set of parameters named for their origin in a hybrid equivalent circuit model. 'F' is from forward current amplification also called the current gain. 'E' refers to the transistor operating in a common emitter (CE) configuration. Capital letters used in the subscript indicate that hFE refers to a direct current circuit.http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=1446653&url=http://ieeexplore.ieee.org/iel5/5/31082/01446653.pdf%3Farnumber%3D1446653QuoteThis is not complete true. Most manufactures state |Z| at 100kHz and ESR as a function of D at 1 kHz or 100/120 Hz. Z = impedance = (R -jX) or ( ESR and reactance). reactance = 1/(2pifC) and ESR = D x reactanceBecause at 100kHz the jX of Z is neglectible for large enough caps, ESR will be the main part of Z. My home made ESR meter measures down to 100 nF and even lower. A very good 1 nF cap with a low D of 0.001 has an ESR at 1 kHz of 159 Ohm. So that is why it is more convinient to measure at higher frequency. But you can not measure C with 100 kHz because the appearant capacitance there differs a lot from the true capacitance. That is why 100 Hz and 1 KHz will stay standards for measuring CBut if capacitance is dropped a lot, Z will be higher. An impedance meter shows you there is "some" problem. But not if it is ESR or capacitance. The peak will only show the ESR and that can in some rare cases (got some samples here) still be good . And because the peak measures C using DC it will show a high capacitance so it seems like that cap is still good. But again, for 95% of the cases it performs very good and is a nice help next to your standard scope probing for ripple curents.I tested some power MOSFETs a while back in Ton and Toff and beside a function of Vgs this is also a function of Id and Vds. A 600V 20A Fet is a lot slower at 15V and 1A

author: Salas
author_rank: Frequent Contributor
timestamp: July 05, 2013, 12:11:58 pm
content: Quote from: PeakAtlas on July 05, 2013, 12:00:56 pmCheers. BTW congrats on DCA Pro, its a most versatile little beast.

author: Salas
author_rank: Frequent Contributor
timestamp: July 05, 2013, 12:29:36 pm
content: Quote from: PA4TIM on July 05, 2013, 12:10:40 pmI agree, its a multifaceted parameter.On another matter, the one of Vbe reading both on DCA 55 and Pro, I have seen that Ib is chosen in the mA. That one helps to max Vbe. Alas, its not representative of small BJTs in average biasing when in circuit. It would be better for Ib to be selectable in identify mode or about 100uA. Or not? Was high Ib chosen so to encompass power transistors, Jez?edit: Here is a 2N4403 by ROHM. It would show no more than 0.65V Vbe in most circuit applications within its dissipation ability.

author: PA4TIM
author_rank: Super Contributor
timestamp: July 05, 2013, 12:47:37 pm
content: I noticed that too. I have an early Philips transistor tester that can source so much base current it kills a BC547 in a flash. So you must be carefull setting it up. But the same goes for a curvetracer. The problem will be that all those features make it difficult to operate and most users probably have no clue about how or what to do. They want to know, what is it, does it still work and what pin is what. And the Peak is good in that case as it is..

author: Salas
author_rank: Frequent Contributor
timestamp: July 05, 2013, 12:53:00 pm
content: DCA series is also much used for HFE characterizing & matching purposes with differential and symmetrical circuits in mind. For Vbe also, since it can be decisive for tempco in current mirrors, parallel low noise BJT arrays, and the like sensitive applications.

author: Salas
author_rank: Frequent Contributor
timestamp: July 05, 2013, 01:02:10 pm
content: Forgot to mention: Current hogging in parallel BJT power output stages is a make or break situation and you would want to match Vbe for also keeping individual emitter degeneration resistors low.

author: PeakAtlas
author_rank: Contributor
timestamp: July 05, 2013, 01:03:50 pm
content: Quote from: Salas on July 05, 2013, 12:29:36 pmOn the subject of HFE (and hfe), the main measurement parameter for gain that the DCA55 and DCA75 show is for HFE (DC current gain). Using the DCA75 on the PC it is possible to derive small signal gain (hfe) by grabbing some Ic graphs for various base currents and calculating slopes at various points in Excel. That also allows you to set numerous bias levels to see what works for your desired application.On the subject of the ESR60 and ESR70 mentioned in an earlier post, both of these instruments only measure the real part of the complex impedance of the capacitor, effectively ignoring the capacitor's reactance. That ensures that the reading of ESR is not distorted by the relatively large reactance of a 1uF for example. We have been very careful to ensure that the ESR measurement is accurate and extremely representative of the real part of the complex impedance. Believe it or not, there are meters out there that only measure the bulk impedance and that doesn't work well for low capacitances even at 100kHz.Turning now to the question of the test current used to measure VBE. It's been a tricky one this. Yes, generally we've derived the test current of 5mA to be as universal as possible for getting a representative VBE measurement for a wide variety of transistors including power transistors and even darlingtons that have shunt resistors across their base-emitter junctions. A small current (of say 100uA) wouldn't overcome the low resistances that are sometimes present in some darlingtons.The user guides for both the DCA55 and the DCA75 has some further information on the base test current used for the gain measurement and for the VBE measurement (gain measurement is generally at much lower base currents of course).The DCA75 however does allow you to sweep the base-emitter current in the PN junction graph, that allows you to see what happens below and above the normal 5mA figure.Generally though, the difference in VBE that you get from a base test current of 100uA or 5mA isn't likely to affect your choices of biasing components very significantly.Regards,Jez

author: PeakAtlas
author_rank: Contributor
timestamp: July 05, 2013, 01:07:27 pm
content: Quote from: Salas on July 05, 2013, 12:53:00 pmI agree, gain and VBE are good parameters for matching purposes. Especially for current mirrors or paralleling applications. I've found that, for a particular variety of transistor (say a 2N3055), if the VBE matches well at one current (say 5mA) then it continues to match well at other base currents too.Jez

author: PeakAtlas
author_rank: Contributor
timestamp: July 05, 2013, 01:13:14 pm
content: Quote from: Salas on July 05, 2013, 01:02:10 pmVery good point. The improved VBE measurement resolution and the adjustable test current that you get on the DCA75 is particularly helpful for this. It's good to keep emitter resistors at a sensible low value for maximising gain, but I tend to play it safe and use a little more resistance than I can probably get away with, especially for applications where the transistors may get hot, VBE with it's negative tempco can lead to problems especially if transistors are unevenly heatsinked.Jez

author: Salas
author_rank: Frequent Contributor
timestamp: July 05, 2013, 01:13:44 pm
content: Quote from: PeakAtlas on July 05, 2013, 01:07:27 pmEventually, that would have been my next questioning post about, was already in preparation.If the Vbe reading at 5mA Ib is a good indicator that two matching BJTs will generally match Vbe at other Ib current levels also, then its enough info for quick shifting through a batch.

author: Salas
author_rank: Frequent Contributor
timestamp: July 05, 2013, 01:43:49 pm
content: Quote from: PeakAtlas on July 05, 2013, 01:13:14 pmJulian Vereker would have been chuffed with DCAs in the hands of his production line staff. Can make a pocket tester, but can't turn back time...Yet.