Hi, You ever had one of those bad days when you just do something incredibly? Oh facepalm stupid. Well yeah, that just happened to me today. I was some just checking the calibration of my little microcurrent test jig here. this is the 1 amp one.

I've got several of these for different current ranges and things and this is the production test jig that goes along. and you know, Bang bang bang bang. You put it in and check the micro cards in production. Um, this I sent these to my assembly house I don't and do them here so they're the ones who operate this.

and I've got a precision current source that I've built and uh, if you want to I don't know. have a showing inside this before. it's it's it's not pretty. Um, there you go.

It's not pretty, but there is a small board down in there. we jump is pretty schmick. Actually, it generates a really precision 1 amp current so it may not look like much. But anyway, this generates the current reference for the micro current calibration and I was just checking the calibration of this where I actually feed in one volt into the input into this thing.

So it simulates the 1 volt output from the micro current using my voltage reference here and you'll notice that it's some reasonably close to I've just switched this thing on, so let me plug it in and watch what happens. Oh Am I doing it again? No. Look, it's dropped down. There you go.

Why is it dropped down from the nominal 1 volt? Well, obviously the output of this voltage reference is being loaded. Why? Because I did something incredibly dumb I hooked it up and I had my voltage reference set to 10 volts. Oh, and this thing is powered from as you can see to coin cell batteries, so there's like a maximum of a 6 volt range on a 6 volt power supply on this thing. In fact, it's dropped a little bit down below that on the rail itself.

And of course, though, if you feed ten volts into the input in this case, the inputs are terminals here are connected directly to an Op-amp on here and if you feed 10 volts in when you got a six volt rail, wah, and well, yeah, something's loading it down. So I think I've killed my input Op amp here and that's you know, my dumb I didn't ruggedized this thing like I would have normally did I did a real hurry and I didn't put any input, input, series protection, resistors, or anything. any input protection at all. any sort of clamping because it wasn't going to be ever used in a scenario where that was likely to be a problem except when it gets back in my hands.

and I completely screw my own design by not checking before I plug the damn voltage reference in. Ah, Unbelievable. So yeah, I think there's something seriously wrong with that chip is loading down my reference? Let's go measure it. And by the way, if you haven't done seen, this has just got a power LED in here and an inspect and that's basically it.

It tells the production operator go/no-go whether or not a micro current passes the test and well, let's this is the voltage input here which takes the output from the micro current and when you feed in the nominal one amp sight into the micro current, this is just a feed through like that. So this just feeds what feeds the currents straight through like that. So no big deal Duh. obviously.

Wow 60 Ohms there you go. That is why it's loading down my voltage reference I've definitely well actually killed it. This is supposed to go just directly to the input of a high precision CMOS Op-amp so it should effectively be. you know, infinite input impedance basically.

and nope, it's shorted out so he whoops you and it's going to be that puppy there. the OPA 2376 So it takes the input directly from there. And the gist, it's it's a window comparator so it drives the LED there from a voltage reference on the board so you know it's a fairly simple device. But yeah, I had no input protection or anything like that Oh suck up the chip and well I hope I got another one I usually buy more than what I need You know if I if I was building one of these I wouldn't just order one Op-amp you know cuz I would have got it from Digi-key or maybe you know someone like that I would have ordered at least a couple of spares Gonski and a little bit of cleanup there and she'll be right ready for a new one.

Okay, so make sure dumbass Me's got it around the right way I think I have I've already tacked down one corner pin and in this case, it was unlikely to have taken out anything else on the supply rail. and I checked the voltage reference on here. it seems to be working just fine and the other Op-amp on here, its functionality is just fine. So there's only basically three main devices on the row here, and sure enough, today, I'm not sure if you can see that, but anyway, a green light.

it's um, inspect and I can now go out of spec and make it jump in and out of spec. and now I can go in and tweak it red. Takes actually quite some time to actually re-check and recalibrate this thing, but there you go. it's fixed.

So dumb. Ask me what's the moral of the story? Water? Do this video I don't know I just want to share my screw-up with you. So before you plug stuff in, thou shalt check. voltages catch you next time you.

You.