Hi I Got an excellent response from the previous blog on the Gausian resistor. uh, distribution and measurement and how you can expect uh well, what can you expect from a plusus 1% tolerance resistor and there were quite a lot of people asking me to do more measurements to get some uh, get a another brand of uh, another brand of resistor that you know, a cheap one, low brand uh type and also 1% metal film same as last time but a different brand instead of of a good quality Phillips one what would be the result? good question and also get a 5% carbon film one and see what would happen and a whole bunch of other things. So I've done just that. Here we go: I got a couple of boxes of Uh 1,5% Uh carbon film and 1% metal film and yes, they are direct from genuine from the one hung low.

Factory in China Let's go and the other thing I thought I'd do is kind of semi-automate or try and automate as much much as possible the process of measuring and logging this data cuz before I just used some alligator clips and I hooked it up and I read the value off the multimeter, typed in the spreadsheet press. enter disconnect, reconnect to the next one and well, it wasn't that much fun now. I got a box of a th000 resistors I'm going to hopefully try and do a th000 of each type. that's 2,000 resistors.

Not going to use these leads I think I'll spend at least an hour or two. just start jewelry rigging something. see if I can get something semi-automated and these are the resistors we're going to be measuring today. Genuine one hung low I Love it and uh, here we go.

There's a th000 bandal 1% 50 PPM metal film resistors and we've got uh and just to represent their lower quality plain cardboard case of course, direct from the factory, we've got our uh, 5% tolerance uh, car carbon films Three band and they're both onek, of course, exactly the same as before I thought I'd keep that, uh, consistent. So there you go. let's give these things a go. And of course, one of the first ideas that sprung to mind to automate this thing was some sort of feed mechanism with uh, guide rails top and bottom.

like this, you know, thin little guide rails that, uh, kept them positioned and sliding through some sort of jig like that and then, uh, some sort of probe which either, uh, pushed down on top so you would, uh, pull it through. uh, one extra resistor, You'd push down the probes onto the top. uh, and then you'd move it along and so for but um, the problem with that is that unless you actually, uh, go to the trouble to add like up Motors and rollers to actually um Advance this thing a certain amount, you've got to do it by hands. You've got to do it by eye anyway And you've got a And it's almost a two-step art process If you pull it through and then push it down something like that that then um, you know you, you've got two hands on that operation.

How are you going to um, push some button to enter the data in if you have to do that or something like that and then I uh. had the idea not of a push down one, but I had a similar idea. maybe using um, some battery spring terminals or these um, hangers even. You know something like that where these set in some sort of jig instead of pushing down they would you know and and you would pull it through like that and it would, uh, you know, make contact like that.

but H you know the surface isn't that great and you've got to rely on the tension of the resistor and it can pull out and it can short to the ones next to it and ah, it was all messy I didn't really like uh that Approach at all and it just seemed, um, too complicated. So unless I did actually go to the trouble to, uh, physically automate the thing with you know, a hydraulic uh thing that came that comes down and motors which Advance it. they know the the average distance and it can step it through and stuff like that, it probably wasn't worthwhile. You're probably better off just doing it uh, by by hand, especially when you just got like a one-off situation like this.

and this is actually quite, uh, common in the industry. If you're if you're a beginner or you're studying and you wonder what it's uh, what some of the common things you do in the industry, well building custom test jigs like this is one of them. um, you'll find it's very common. I've built countless ones over the years over the decades to uh, test various things test Concepts test Pcbs and all sorts of stuff.

So building up uh, jigs like this and uh, having to automate them um is a skill which you're probably going to need sooner or later in Um Electronics engineering. But anyway, I decided to uh, uh, simplify it and just do a hand based system. So let's take a look at that and this is what we're going to use today. We're going to use what's called a Pogo pin and these are H like an industry standard way to build.

uh PCB Test Jigs and things like that, they're really great and as you can see they actually plunge down like that. So they're also called plunges. So if you're search for uh like a uh plunger pin or something like that or a serrated plunger as we got here you can see that on the on the tip of it there is actually all these little serrated jaggy sharp points and you can get many different types. You can get ones with a single sharp point that are designed to penetrate oxide on a PCB In this case it's multiple sharp points which is exactly what we want for going on to a resistor test lead.

I Think you can get ones that are uh, concave as well like they go over uh test posts and things like that. In this case, the one we've got here is the um it's from F now/ Element 14. There it is. It's a serrated uh plunger and they're quite cheap.

They're only you know, a dollar each or $2 each and they're available in many different types. many different Uh widths as well. This is a 1.6 mm wide uh one. So so you drill a 1.6 mm hole or 1.5 mm hole um, in your uh, in your whatever you're using as the basis for your test jig be be it a piece of uh, clear, clear acrylic, uh delin, or uh, you know, any type of those engineering materials.

But what we're going to use today is just this little uh, prototyping board and uh, hopefully we're going to um, install these on here so that we can actually get a uh, just a nice little hand uh you know, just a little hand press uh board that allows us to press down onto the pins. Now normally you would uh drill you would use it like a this This is a board as a template and the pin would you know you drill out a certain size hole and then you'd put it through like that and you'd glue it in place. And then you can do all sorts of clamp mechanisms and I've U I've showed examples of these. uh test, Uh, these test PCB test beds before, but in this case we want a hand based uh test so that we can just, uh, push down with our hand onto the resist pin.

Now the problem with this is that uh, it can. You know because it's got those serrated uh pins on the top there. Once it bites down on there, it's pretty good. It's not going to slide off okay, if you got one with a single point.

of course that won't work. But these serrated ones work nicely and even if you get it sort of on the edge, it's still going to bite in there nicely. Like that they are. They are actually really very nice and they do a really good job of biting on to that lead.

And because they're very sharp, they got very sharp serrated uh Jaws on there. Then it should bite through the um in the oxide. Any oxide on these resistor leads and trust me, there is going to be oxide. Even on brand new resistors, you're still going to get that so you've got to avoid that.

So these this is probably an ideal uh plunger slsh Pogo pin for this application, but unfortunately it's not big enough. ideally I'd Want you know? like a real huge thing. So because this is aign by hand, it's not some automated machine. ideally I'd like a big fire 5 mm diameter one like that, you just get bang.

you know, even Stevie Wonder Could probe this thing. but because this has only got a 2 mm uh, head on it. It is possible to miss it like that and you know that' be a real that can be really annoying. It can, uh, ruin your day and waste a lot of time.

So what I'm going to do is widen that to a 4 mm Pogo pin. I'm going to solder a couple of pins together like this and then bang. Even if you miss one of them, you're still still going to get at least one. and if you get both on there at the same time of course, then you're going to have both come down.

But I think that's going to work pretty good and there's a fair good margin for error there when you press that down. So let's try and use two Pogo pins each side. Now it just so happens that this borders I think are really quite a nice width for this particular job. So if we put two pins on one end of the board and then two pins up on the other end of the board, then that's a fairly good distance.

You don't want to get right into the resistor because if you've got the thing laying on the bench like this, you know there's going to be the, um, the resistors. Actually, because the body is thicker than the lead, It's uh, you know you don't want to probe it right in there like that. You want to probe it out here where it's flat on the bench. So I think we'll just uh, put two pins on this side and two pins on that side and it'll be hunky dory now.

we can't lay them flat of course, like that, because if we laid them flat flat, then, uh, uh, obviously they're the wrong orientation. They'd be like that. We want to flip it 90 like that. So I'm going to, uh, tack two together like I've done here.

put it on there. um, strap it down in there, and uh, strap it through those holes which are nice. If we line it up, say there. we can strap it through this hole up here on the top.

Like that, strap it through that hole and strap it through the hole on the other side of it, hold it in place, put a buttload of solder on there, and it should hold it really, quite firmly. And here's our completed board: I Think it uh, worked out quite well. You see: I've uh, put those uh pins on vertically like that. I've put two straps up here like this on the ends here and solded them on the front and that should be reasonably, uh, robust and should, um, last for a fair number of uh, well, you know, uh, test um actuations I guess and all I do is hold it like this.

It's not bad. hold it in one hand and I can just go press like that and each resistor I can just go along Bang Bang Bang Bang like that. I've got to be careful, of course not to have my fingers too far down so that they're touching these terminals here. I could strap that with some Uh tape just to make sure.

In fact, I probably will strap the whole thing with tape and then bang Bang Bang Bang bang I can go along like that. Brilliant. I Love it. And here's the completed unit wrapped up in tape: I've got some some uh, reasonable length uh leads on here.

about a foot long. um, just for flexibility into uh, 4 mm banana plugs and uh, I can't accidentally touch those pins so there's no question about that. and I Rather like that, it works quite well, but let's test the repeatability of it, shall we? So I'm going to uh probe a resistor here. bang There we go 1.03k and let's uh, wiggle that around.

jiggle it like that, probe it again. same resistor, same resistor right up the top end. Bang Bang only light pre light amount of pressure, tiny amount of pressure and looks like that does a really excellent slide along. Does a superb job.

more than repeatable. Very happy with that. So part one solve. We've got a semi-automated anyway way to probe our resistors.

Beautiful. Not as efficient as a fully automated one, but it's going to save a hell of a lot of time having to uncp two Uh and Uncp and then recp uh two alligator clips onto each resistor. You got a th000 resistors or something. That's just crazy, so this should help automate that.

The second part of it, we need to automate the actual Uh measurement or once again, semi-automate this measurement. Now ideally I'd like to use my HP 3478a which we used last time cuz it's the highest uh, highest Precision highest resolution uh instrument I've got in the lab here, but unfortunately it's only got a old school Gpib interface there and uh well. I don't have any uh Gpib uh cards anymore. I've probably got an old Isa card somewhere.

but I don't have a computer that has an Isa Port anymore. Crazy. So we're going to have to ditch the 3478a. Bummer.

And uh, we're going to have to use use a data logging multimeter. so I thought I'd use the Agilant u1272a. Now, whether or not we use a handheld mum meter like the U1272a or the HP 3478a bench meter, it, the process is pretty much uh, the same. You want to connect it up to the PC and you want the PC to automate the measurements.

Now in this case, uh, ideally what I'd want is for every time that I push this down onto the resistor I would like for the software to automatically sense that I've probed the resistor, waits for the reading to stabilize, takes the measurement, saves it to the Excel file, and then uh and then doesn't take another measurement until I physically disconnect it and it measures an open and then it starts measuring the next resistor. and and so I don't have to actually press any keys because the thing that took up all the time last time was pressing the keys. of course I'd have to uh I'd have not only I'd have to hook on the alligator clips I'd have to read the measurement, type it in, press enter into the Excel spreadsheet and make sure I got it right too. So you know, prone to um, you know, human error there.

But ideally I want the software to just bang Auto sense that it can do that now. I've looked at the software for this, the U 1272a the Agilant data loging software and it doesn't seem to have the capability I can upload the measuring results from there. this I can, uh, start, uh, data loging, measurements and stuff like that with time intervals and triggers. But yeah, it doesn't really do what I want.

But aha, here's where I don't have to muck around. Oh sure. Okay, I could write my own software right? I could you know write a little Visual Basic program or whatever some script which uh, talked to the commands and issued them and did all that. but I don't want to waste my time I just want to take some measurements and plot some data.

So this thing has got uh 10, ,000 sample s 10,000 sample memory built in. so if you only want to measure a th000 resistors, not a problem. We can uh, push each one, press the button bang store store store store like that. so let's give that a go.

Now the u1272a actually has uh, three different data logging modes and we can uh, get into it here by pressing the setup and going into the dlog or data login menu like this. Now we can then select which data loging mode we want. uh trig, we can do uh hand mode or we can do auto mode now. Uh, the hand mode sounds like the one we want.

That's basically where you manually push a button to store each measurement. Uhhuh. But there's always a trap. if you read the manual, it tells you that it's only got for some bizarre reason.

100 sample memory. Uh, you know, 100 samples in this mode? not the full 10,000 crazy I don't know why it doesn't tell you why. Um, so if we look at the other modes, auto mode is like an automated time interval, so it'll take one sample every second or once per minute. Or once per hour or something like that.

We don't want that. Obviously, we want to store them manually. So as it turns out, we can go into trigger mode now. not what this mode is normally used for is.

uh, you can set it up so you know if it goes over or below a certain threshold or something like that, then it will, um, like if it finds a new Min or Max it will uh, it will store that um event in in the data memory. but well, you know that's no good. But it also has a mode uh, where exactly the same as the hand mode where you can just press the uh hold button here and it will store it in memory so that's the one we want. We'll use that, we'll select that, and uh, we'll go out of there and we'll try and Sample this into memory and we'll start data logging by holding down the log button here and as you can see, it popped up with the first event there.

it pops back to the temperature there. I Don't know why. um I Don't know how to get it to stay exactly on that thing, but as you can see, it's got log written up there and let's prob our first resistor. Any resistor doesn't matter and uh, let's press the trig Auto hold button down here.

that's pretty stable and bang. it's uh, right, it's we're on trig Auto hold mode now and if we press it once, bang, we've stored it in and as you can see, it's automatically jumped to number two. So we get the next resistor here and we press it again. Bang it uh automatically settles the reading and jumps to number three.

It really is quite nice and as you can see, it, four, five and we can go along and bang that is. That is really quite neat. We just press a button, probe, press, probe, press and everything's happy. Now if we go out of log mode once we're finished assuming we've done, say 1,000 resistors or something like that, we can go into View mode by holding down view down here and as you can see, it's got seven events and we can toggle through those events.

Bang that. we measured there we go. The first one was open I don't know what it did there, but the second one. Bang Bang Bang bang bang and there you go and we can upload that data later.

Once we''re done our 500 or th000 resistors and upload that to the PC, save it to an Excel file. Nice. It looks like we've eliminated at a fair bit of time uh, not only uh and and operate potential operator error by typing in the values manually into the spreadsheet. What we got to do is push a button to store it and you know what I've discovered I was going to use this trigold mode where you have to push the button but I found that you don't.

You can actually use the auto Hold mode in log mode. I'll show you watch this. Okay, let's reset it and this is absolutely brilliant. I won't have to push any buttons.

watch this go into log mode. Okay, I'm still up to event uh, 12 12 but you know we can start from event one and we hold down trigold mode and we're in Auto hold not Trigold mode and we go in here and we just push it on there. it it takes the stable reading and then it automatically saw that it logged it in to the next event and let's probe the next resistor. Bang 14.

There we go and take it off. Disconnect 15. It automatically is logging and storing each resistor. I Think it's brilliant, but it seems if you do it too quickly it doesn't do it.

like if I go between that one and that one, it hasn't had time. so I'll leave it off a bit and there we go. It stores it again so you've got to be careful that uh, you are actually logging that event each time. But there you go.

This meat is brilliant. It allows us to log these resist without pushing automatically, without pushing a single button, without writing any script or uh, software or anything like that. Fantastic! Now what would make this really perfect is if I could get the damn thing to beep whenever it uh stored that event in memory. I'm going to have to search through the menus here and see if I can enable some sort of event uh, beep function and sure enough, ageline have thought of everything.

I did have the beep uh turned off I went in the setup, turned it back on I mean dat logging mode and watch this I put it on beep event 23 and no I did it too quickly there. That's the only disadvantage to this is that if you can't do it too quickly, but beep 24, there it is I don't even have to watch the meter. All I've got to do is listen for the beep and I know I've captured that resistor. This is this is just brilliant.

It's it's automation that I've only tradition seen in software I Love it and just for a bit of fun. It just so happens that I have a very high Precision .01% metal foil resistor. uh 1K So I thought we'd hook that up and have a look what absolute value we've got I've nled that out I was getting 1K before. it's uh, slightly different.

Now it is uh, 9999. So there you go. It's pretty spot- on. Okay, it's not a genuine calibration, it's a transfer Str standard using a factory resistor.

but uh .01% of uh 1K is .1 ohms or uh, the least significant digit there. So our absolute values are going to be pretty close to spot on. One of the other good things about the u1272a is that it does Delta measurement Uh Auto ranging as well as I said I nulled that uh out. So I shorted those particular leads out and I Actually, well, if you do it properly, it nulls it out like that and there you go it.

But it keeps that on the other ranges too. It doesn't manually range. There you go. it.

auto ranges up to Mega ohms Beauty And of course, before we start, we want to zero this thing out. So let's do it. There we go: I Like it and is it repeatable? Yep, not a problem. Okay, I'm going to do a quick sanity check here just to make sure we're getting repeatable Um.

values using the auto hold function. So I'll go Uh, 9951 9956 9966 Now, if we go back through and check them again, let's see if we get repeatable results. 9951 Yep, 956 Yep. 60 Oh 66.

It's jumped up to 66. There's a six differential there. Don't like that at all. That's no good.

75 74 Yeah, we're within one. I'm happy if we're within one least significant digit here. 75 Yep. 659 Yep, 61, 59 64 Yep.

Okay, so there was only one that was out by uh, six least significant digits. Let's do that again. Number 366 Okay, so it looks like it's repeatable again. So I don't know what happened the first time.

The first one must have been a bit out. so let's actually get out of Auto hold mode there. and yeah, it's that's exactly what it is 9966 and if we compare them without Auto Hold 51, 56, 66, 75 and wouldn't you know what? I Just played back the video to double check that actually wrote them down wrong and that third one that was six digits out I said 66 but I actually wrote down 60 Bloody Humans Done! And if you're wondering how long that took, there, you go 25 minutes And that included the uh answer in the door for the Cier guy I'm actually, uh, rather amazed at this uh jig actually I really amazed at the uh efficiency of this um setup I didn't miss a single uh single uh reading I didn't get any double readings or whatever when you know if I accidentally touched it twice. It just worked every single time.

Very impressed. 25 minutes for a th000 resistors. that's an average of one resistor every 1.5 seconds and that includes the handling and everything else I Love it! and if you compare that with using the alligator clips I did last time that was about seven or 8 seconds per resistor or there about. So this uh, little simple jig with the auto hold function of this meter has gave me a fivefold increase in in testing speed.

Beautiful! And now we want to upload the data. Uh I've got the meter connected to the USB port via the USB IR uh cable and it installs the driver and it's just a com port. In this case it's a Com4 and we connect to it and it should show meter connected bang There It Is down there. Um, and you can change ranges and do all sorts of uh Jazz Like that but we want the event data login.

It's got manual data login Auto and event. but because we use the event uh mode, we want to um, uh, we want to load this data in here. and bang. Here it goes.

Looks like there's here we go. Well, it's going to take a while and here it is. Bang 1,000 loaded. No problems at all.

And there's the data table for all of our results. and uh, we can export that to an Uh CVS file which then we can load into Um XL or open Office Now there's one really annoying thing with this. uh, Agilant software and that is, uh, the value it actually reads in. Look, it puts uh 997.50 space m So Millie Well, you know.

Okay, whatever. But when it exports that to the Um CSV Uh file, then when you try and import it, it's not going to import that as a number. It's going to import that as a text string with that M on the end. And that's going to make it really annoying to actually, uh, do that.

So you've got to uh, eliminate that M from it somehow and fortunately, you can do that uh, using uh, the space uh function so that it actually um, it. it actually eliminated that M and put it in its own column and then it's uh in this column. Here, you've got the actual data itself, so that's going to work an absolute treat. Bingo There we go.

We've got the Um and we can just, uh, kill that column there. and we've got our data in this column. Okay, I've loaded the data into the same spreadsheet I used in the previous blog, so I won't go through that again. and uh, as you can see, I've plotted all 1,000 resistors on the X axis here versus their percentage deviation from the nominal 1K in the Uh Center here plus 1% to minus 1% And there's two things to note: Uh, The first of all is that the Um spread of the values is around about.

you know that uh, 6 uh value. So it's very similar to that, um, half a percent uh, sort of variation that we saw on the Philips brand resistors. So it's a similar sort of uh, tightness in Spec. But look at this.

it is offset. It's clearly offset. about negative, say., 35 or thereabout on average, through the middle of that offset, there's not a single resistor that is above 1K There you go. That's what.

That's what we found from these one hung low brand resistors It, whereas the Phillips ones in the previous blog you saw were pretty much spot on, the Uh nominal 1K and then they deviated either side. but these one hung low brand ones show a negative offset. go figure. And of course, there's actually no problem with that cuz they're still within the Uh nominal plusus 1% uh, tolerance.

so they're well within it. so not a problem at all. But uh, the problem might come in if you're uh, relying on the fact that the Uh nominal manufacturing mean is going to be centered spot on 1K right in the center there. and maybe you parallel 10 resistors up and you expect some to be high and some to be low and you want them to average out to a better, better tolerance resistor.

Well, that's not going to be uh, the case this time. they're going to actually, uh, um, average out to a value of around aboutus 0.35% from 1K Something to watch out for. And if we take a look at the probability distribution histogram here, it's a very similar Galan type uh response like we got with the Uh Philips resistors. Pretty much exactly uh, as you'd expect.

but look, we've got this little um, outlier one down here at minus 1% There's a few items right out there that have popped their head out, so that's rather uh Curious And of course, here's the center line. You can see that uh- 0.3% or so um, offset. Now that's for uh, 21 bins now. Um, if we go down here and increase the number of bins, you can see that the center here isn't actually a nice smooth um response as you'd expect, Theyve you know, down at this 0.3% there's a majority, then they've got another .35 and then the next bin up goes up again.

so it doesn't really. um, follow that uh, classical, uh, bell-shaped curve as much. uh, but you know you could do other bins, but you do get the Um bell-shaped response up here so you know it's near enough. But once again, those little outliers at minus 1% have just read their ugly head.

There's nothing in there at all, and there's nothing in um under um, Well, on the Um. on. on the positive side here, there's absolutely not a thing. Once again, you can see the offset, so it's rather curious.

And naturally, of course there a few people in response to the uh, previous episode um, were mentioning the fact that I didn't mention uh, standard deviation and I didn't really want to. You know I don't really want to get into uh, standard deviation and how that it was. The response is pretty much what you'd expect if you, um, get what's called a six uh, Sigma response for 1% Um, especially if it was centered. If you remember the uh, previous uh blog than the odds basically, um, the uh, the Sigma um response and how many uh Sigma you design for will basically dictate the the probability of getting a resistor or getting a value right out at these limits.

Um, right out here. and um, that's probably what. uh, well, Phillips actually designed for? They may have designed for a Six Sigma response for 1% over that range, but H You know you don't really know um, unless you're the manufacturer to know what actual system they put in place. They may have been uh, working to Um 3 Sigma half a perc instead of uh, um 6 Sigma 1% for example.

So anyway, if you want to look up standard deviation and Sigmas and how it how it applies to all this statistic stuff, there's better places to learn that than here. But there you go. It's a rather interesting uh response. So we'll try the Uh 0 point uh, sorry, the 5% uh tolerance carbon fil resistors and see if we get a different response.

I Think we will. All right? I'm not a happy little camper. I'm trying to upload my 5% resistor data and I've tried restarting the program, restarting the meter. The data is definitely in the meter cuz I can view it in there.

but I try and load it up and it just doesn't load anything at all. It's nuts. What's going on? Look, it won't even call up the menu anymore. This is a heap of crap I Don't know what's happening with this bloody software.

It's just locked up Every time it gets to the first uh loading in the first uh data item, it just locks up and then that's it. and well, you can cancel out of it, then it won't load again. Tried reinstalling the software and doing all sorts of stuff and it just doesn't work I don't know what's going on. Unbelievable.

This The data is in here. Here it is. Look, look there it is. 1,1 1,1 samples.

If you go back to the first one there, it is. there's the first sample overload. Next one's 2K I Don't know what what's going on there, but there you go. There's all the data and it's in there.

Why can't I Bloody well extract it out of here there nothing. I Hate worse the tools that don't work. so I had enough for today. Damn it.

I'll finish editing the video upload it. Sorry, but you don't get to see the uh 5% resistor data. Send your hate mail to Bloody. Agilent.