Hi welcome to another Evie blabber episode this one I wasn't going to do because it's rather embarrassing. but I thought hey, this could be a learning experience for some people. Now this is my EDC Cronkite MV 106 Voltage Standard if you haven't seen it before, I'll link in videos down below very nice metrology Regrade Voltage Reference standard and I was testing a multimeter the other day plugging it into it and I as usual I set it for 10 point Zero Zero Zero Zero Zero volts and this thing is absolutely bang-on I've had it tested at a Traceable Cow Standards lab and this is what I got Ten Point Four Seven o' Volts now I Sort of freaked out for a second because I actually had the multimeter switched to Ohms when I actually plugged it in. and of course, in Ohms mode, the multimeter will try and generate it, will generate a voltage, and try and generate a current into this thing.

and I've done that before without problem. but I was sure that this thing actually worked before I plugged in that particular multimeter on the Ohms and as soon as I plugged it in, why am I? All of a sudden it was giving out ten Point Four Seven volts And look, if I switch it down to nine here, well, it's it's still Nine Point Four Seven. So it had all that resolution, right? So it had all the typical resolution there so it seems to work, but it was out. And if I turn it down to a hundred millivolts here, right? it's bang on of course.

And if I turn it down to ten millivolts it was bang on Again, it was only the 10 volt range like this. so I thought no I've somehow this multimeter in Ohms range is blowing this thing. but I knew you know like that's a real remote possibility and because yeah, this thing's only going to generate like a milliamp at most and this thing is pretty robust. it's going to handle that as I said I've done it before but hey, those were the symptoms and you know, look, it's not a Dickey connection or anything like that and I turn it negative and we get the negative and it works fine on the 100-million got range.

So I thought you know somehow I've blowin maybe the output of an Op-amp or something in the feedback loop or something like that, you know even though the remote possibility what it was and that was that was what I got. so I thought you know what that's got to be like the problem and I thought oh great okay I can do a repair video this I got all these super excited that you know I'd be able to actually repair this thing because it's a nice you know or through-hole design and and everything in there. So I got all excited so I moved it over here and onto the main bench where I shoot videos here. We took the lid off like this and then I realized oh what the problem was and no, it's not blowing.

it's a peb kak. problem exists between keyboard and chair ie. me I fooled into thinking this thing had failed you to various circumstances. but it hasn't now.

if you want to try and figure it out, pause the video now and try and figure it out. So Tweedle my thumbs until you go on. Pause it. try and figure it out.

You should be able to maybe not buy what you actually see here, but buy a bit of deductive reasoning. You might be able to figure it out. And as I said no, it's not dickie connections down here like this. We've got our sense terminals there.

Everything's just fine. So what's wrong here? Well, it is those sense terminals. Watch this tada look at that. It wasn't making contact on that sense terminal and if I put it negative like this.

Bingo. The negative one also was like just a smidgen out. it wasn't making contact. So these sense terminals here of course in these sorts of instruments and not only in these metrology grade instruments, but like a 4 Ohms terminal measurement.

That's what you have to have here. A 4 Ohms measurement because you have to sense right at the load. In this case, we don't have to. Hence, we can use these shorting bars here because the molding made a load is only 10 mega.

Of course it's very very small and these wires here they only like a million or something. So do Ohm's law. You can figure out the voltage drop across these cables is bugger all. hence why we can just sense here.

but larger loads we'd have to sense there anyway. that's what it was. just a tight and it wasn't tight on there, you know? I wiggled them around it look like they were in, you know, but it was only like, you know, a smidgen, like half a turn out or something like that. That's all it had to be that it just didn't make good enough contact is the tiny tiny smidgen out.

So there you go. a trap for young players. and what's happening of course is that the feedback loop in here. If it's got no sense, if it's not reading that sense voltage back, it'll just go to full-scale So obviously that's what it's doing.

it's going to what. ten point five is full-scale and then negative. Ten point five down. there is full-scale and that will of course change even if you go down like that.

So that's what the problem was. Oh yes, it's incredibly embarrassing. I Thought that might be a lesson for some people. don't assume something's foldy.

I Got a bit too excited that I'd be able to do a cool little repair video with this thing I think rather than think about it. but I ultimately did discover the problem pretty darn quick so it's not that embarrassing. But anyway. I thought I'd share.

Hope you learned something there. Catch you next time.