Hi. Just a quick two minute tech tip video to do with multimeters and a feature you may not have known about with your multimeter and one you probably won't find in the manuals. Hmm, I should update my manuals to actually include this. If you've got a multimeter with a temperature functionality, most you know any decent multimeter is going to measure temperature with what's called a K type thermocouple.

They come in different types, but almost all multimeters use K type Thermocouples has to do with the composition of the metal that's used for the two wires in here. I've done a whole very extensive tutorial video on thermocouple, so I'll link that in, up here and down below and at the end. Check it out. Anyway, you might know that uh, some more advanced multimedias like this 121 in this keysight uh 1272.

I might actually have an internal temperature sensor that actually tells you what the internal temperature is of the multimeter. And of course if we got done uh, temperature mode at the well, it's to do explain that in a minute, but if you plug in Uk type thermocouple of course then it measures the external temperature on the thermocouple. And of course if I touch that boom it goes up like that. and likewise over here we plug it in and it goes from overload to measuring.

Uh, the external temperature there? But what if you've got a multimeter that doesn't uh, have that internal Uh temperature readout display like this one or this one or countless other multimeters that will not measure just the ambient temperature can be handy to measure the ambient temperature sometimes. So how can you do it? And you forgot your temperature probe? Of course you can just plug in your temperature probe and Bob's your uncle, right? But if you forgot or don't have your temperature probe handy, how can you measure it? Aha, it's easy. All you've got to do is plug your probes in and short them out. Like that.

there is your ambient temperature, believe it or not. And yes, this should work with, uh, practically any multimeter that measures temperature. There it is 24.5 We can now measure the ambient temperature of the room without a thermocouple. Brilliant! Now there are some oddball meters like this Fluke 17b that will actually measure the ambient temperature or it will try to look.

I rub my hands over there and it's it's. all over the shop, but it doesn't show open like um, other meters including other flukes like this. And you can do exactly the same thing though. you can plug that in and it's all over the shop and we do that.

And bingo short our pros: We've got our ambient temperature. This one's reading a bit higher. don't know why. So why does this work? Well, there's a very specific reason for this, and I've gone through that in my extensive thermocouple tutorial video.

but it has to do with the Seabeck effect and how thermocouples work. In this particular case, when you shorted out like this, we actually read zero millivolts. But every multimeter that measures temperature like this using K-type thermocouples must have an internal temperature sensor somewhere, be it built into the multimeter chipset, or it could be like an external little Sot 23 temperature sensor or whatever. It's got to measure it internally even though it doesn't display it.

and by shorting out the probes like this, you are basically you know, shorting out the input so it generates zero volts like that and therefore it defaults to the ambient temperature. It's measuring with the internal temperature sensor and this is either done with like a lookup table or with like a polynomial function and watch my tutorial video. Won't go into the details, so when you short out the probes like this, it basically thinks that the external temperature probe is at the K-type probe is at ambient temperature. so that's what it displays.

So this is why your meter can often do weird things. If you've got it on temperature and just have your probes flapping around in the breeze like this, it's fine if you short them out because it's measuring like, um, in the order of uh, you know, micro volts and there are differences in meters like, uh, you know this one. Once again, it's got dual readout measures the internal uh temperature and of course, if we plug that in, it'll work just fine and dandy and other ones like this Tektronix for example, it's a little bit out and you'll notice I'm putting my finger near the thing. I'll rub my feet on the capital 54.

It's just like, yeah, it's all over the shop like that. But of course, if we plug our probes in like that and we short it out, it should get to the ambient temperature, although that one's going a bit high and this should work with any meat on the market, because anything, as I said, that uses a K-type thermocouple must have an internal temperature sensor, because that's the only way that it can accurately, uh, measure and compensate for. The K-type thermocouple like is designed to be used with these meters. You can't do it any other way.

And just to prove that, this is a legit thing, and it is measuring the ambient temperature and not just some uh, you know, pre-programmed internal uh, offset or something like that. I've got it inside my thermal chamber here, and as you can see, it's pretty darn close to that internal temperature. Just be aware of the thermal layer because the temperature sensor is inside the plastic case and inside a rubber holster and all sorts of things. So yeah, there will be a quite a significant uh temperature time lag there before the ambient temperature gets inside the meter.

So there you go. I hope you might find that little tip useful one day. And as I said, go check out the extensive thermocouple tutorial video I'll link in because it there's a lot of uh trick and a lot of uh science that goes into uh, the materials in the K-type thermocouples and the algorithms and lookup tables that multimeters have to follow to in order to actually get accurate uh temperature readings using these, uh, dissimilar metal thermocouple probes. It's really interesting stuff.

If you liked it, give it a big thumbs up. Catch you next time.