I was taught this when I was in the military, to ensure our cold-junction correction was working before using a meter to measure an external temperature. Over the past 40 years I had totally forgotten about it. Thanks for the reminder!
Yes, I should have mentioned that actually. If your meter isn't at ambient temperature internally before you take your thermocouple measurement then your reading will not be accurate. This is a way to double check that.
@@EEVblog are you sure about this? I always thought the thermocouple measures temperature difference between junctions, so whatever temperature is inside the meter shoud work as long as it's measured accurately internally.
@@kaziq Why would you need to measure ambient temperature in this case if the reading does not depend on it? As you said, thermocouples measure temperature difference between hot and cold junction and the cold junction is at ambient temperature so you have no way to know the absolute temperature without ambient reference.
@@maximgusanu5294 I didn't say you don't need to measure the ambient temperature. My point is that the temperature inside the meter does not have to be the same as the ambient temperature for the measurement to be accurate. Dave said it has to be the same, but I can't understand why. You say the cold junction is at ambient temperature, so where is the cold junction physically? If it's inside the meter, what does the ambient temperature have to do with it? You only need to know the temperature inside the meter (as close to the junction as possible) to know the cold junction temperature, no?
@@kaziq I think the cold junction is inside the thermocouple jack, not inside the meter, so the point is that the internal temperature of the meter has to be the same as the temperature of the jack.
Agree. Video 5 minutes 59 seconds long. Opening with an ad about gut health and taking a big, healthy dump every morning by a Dr. Gundry. The ad was 47 minutes 55 seconds in length! At the end of the anticipated video is a very boring 11 minute 11 seconds ad scrolling the side effects of the latest immunosuppressive drug. That's a two minute 'quick tip' expanding into an unwieldy one hour, five minutes, and five seconds long video production. Yes, I checked the timer and let it run. Went through three soft fried eggs, two English Muffins with sweet butter and homemade lime marmalade. Full pot of Folgers. Guess that now I will have to watch the 'two minute tip', skipping the ads this time. Are all Australian tech tips long winded?
5:01 The lag for ambient temperature issue is a good reminder that this works both ways: if you're using a thermocouple and just moved the meter to a different environment, you need to wait for the meter's temperature to equalize or the thermocouple reading will be off.
Yep, and these multiassumpters (not to be confused with multimeters) may not even have correct LUT/polynomial for temperature. Mine 838 shows over 1000C at 400C soldering fan, but it is totally accurate at 0C and 100C. That's probably because it is calibrated only by these two points
@@thecakeredux I kid you not, I've seen an actual product (Chinese weather station) that let's you log the temperature in radians. I guess the company was like "yeah more features, more sales".
HVAC installer here and “retired” controls engineer. I check temps every install with a temp tool and didn’t even think to use this feature and keep the thermocouple around as either a backup or bring one less tool. Great stuff!
The standard probes are a thermocouple junction whether you want them to be or not. Copper wires with plated probe tips. Fortunately the voltages produced are small.
Now for the most important question, Dave? Just how many multimeters DO you have??? A guy with one meter knows what the temperature is; a guy with 2 or 3 or 7 or 8 is never sure.....
Thanks for the tip mate. I knew how this all worked but I would never have thought to short the leads to get an ambient temperature reading. That's bloody brilliant! Honestly I feel a little dumb for not having thought of it myself. Live and learn right? Works on my Fluke 179.
Clever. I check the fuse in the meter by setting the buzzer and put the probe in the mA test socket. When the fuse is in working order it will go through the mA jack to COM.
I just tried it out on a UNI-T UT139C and it works! I also tried it out on a pocket multi meter ANENG AN 8009 and I didn't even have to short the leads out. I sprayed both of them with a can of compressed air and it actually picked it up. This is something I'll remember for life and a little trick I'll show people who didn't even know about it. I always wondered why I did that and I never clocked on n thought there was something weird or wrong going on with the meter. But now I know 👍🏻 Thanks once again Dave for all of your tips 🙂
A few month's back I shorted the leads while changing modes on your BM235 meter. Passed through the temperature mode and was shocked to see it reading the ambient temperature. At the time, I assumed it was just some internal zero reference that happened to coincide with the ambient temp. Cool to know it actually is reading a thermo couple! I shall remember this trick.
Thanks. For same reason after you charge you keysight accu using the stock charger you have to wait for the multimeter board to cool down before you can do accurate thermocouple measurents. When charging the accu and the board can easily go to 35-40*C and so does the reference sensor. Fortunately for this type, you can judge by temporarily incorrect ambient temp indication.
How much I love you and I love your channel. I wish you lasting success ... I am an Arab from Iraq and weak in the English language. I hope you will support the Arabic translation 
The global world of business and technology runs on english as a standard. It might be a good idea to start learning english so you can read the words on schematics and data sheets without the errors that computer translation makes, and freely communicate with other techies around the globe.
@@jenniferwhitewolf3784 Yes, I am struggling to learn the English language, either because I translate the Google translation from Arabic text into English, and vice versa
No way! I never new you could do that. I have a Fluke 87-5 and tried it out and what do you know... it worked! 68.8F. How cool is that! Thanks for sharing this tip!
Wow I've just gone to the radio shack to grab my multimeter to try this cool trick and it works. I've been using My multimeter for years and never knew that.
Might not but I see there are other techtronix stuff that do: uploads.tapatalk-cdn.com/20161113/ee1a2518e0fed6b99c2fb28a87875628.jpg Someone brought one that does on the Eevblog: www.eevblog.com/forum/blog/eevblog-712-uni-t-ut71e-multimeter-(why-uni-t-meters-suck)/msg604683/#msg604683
I've been doing this for years. I thought it was very common knowledge. That being said like you mentioned in the video it is never in the manuals so folks might not be in the know. However on the plus side.. Once you know you know.
I become really interested in electronics in 2009. I came across Eev. I never knew Dave had just started channel. So 12 years or so I've been watching the "Crazy Austrian Guy"! 🤣🤣 Joke ?? I know he's from Austrailia. Anyway he's been in my top 3 ever since....love it
My automotive collage taught me "OL" Does not mean Overload, it stands for "out of limit" 25 years later I find my Fluke manual on line and it states "OL" stands for "Over-load" I'm glad I only remember incorrectly correcting one person...
Never had a temp probe for my Fluke 179. Got it from my old job, and it's been one of the best meters I ever had, just never used the temp portion as I don't have the attachment. The more I know!
I use a cheap hakko clone soldering tester occasionally for the same purpose. It's just a thermocouple in a box with a readout you can put the tip of your iron on to check it's running the right temperatures.
4:25 You have been holding those leads for a while and transferred some heat to them, maybe conductivity of the metal changed slightly due the heat increase so it shows increased temp?
Personally, I think a discussion about the deficiencies of a DVM/VOM as compared to an 11 Megohm or 100 Megohm VTVM or equivalent solid state design might me in order. The HP-410B was the Gold Standard in my day!
15 years in HVAC and I'm ashamed I didn't realize this. I knew there was an ambient sensor in them for the offset, had no idea I could make it display that temp with a simple short. I have stormed out of walk-ins because I didn't have my K-probe or it broke because there's no such thing as a good K-probe.
had to check the date this was released, while at the start of the video very interesting! I dont know how thermocouples work; I'll have to watch your video
Wow, this even works with my cheap-ass, no-brand multimeter! I don't even need to short the leads for it to work. And its reading really matches ambient!
Ok I read the title wrong, I thought you could use one without a temperature feature to do temperature, kind of like how you can use a multimeter with a light meter (e.g. Apogee) and using a conversion factor get the actual light output.
Doesn't work with mine for some reason. Dunno. But it's a cheapo one and it doesn't even work with the temperature reader setting anyway. I put it outside for 10 minutes, and it still showed 22-26 degrees, same as inside. Cool video though, I never knew this.
I always hated thermocouples because they are so inaccurate and drift with time and usage. My first assignment as an electronic engineer was to replace the 10 thermocouples in the instrument from thermocouples to RTDs (Resistance Temperature Detector). They use a platinum wire wound around a ceramic core. The resistance of the wire will change with temperature. The initial resistance is usually 138.5 ohms at 100°C. There are many types of RTDs but this is the most common. With advanced math, solving a 9 variable matrix and 3 simultaneous equations I was able to reduce the circuitry to 1 common op-amp and 4 precision resistors for an accuracy of 0.1% over a range from -200°C to +600°C and a voltage output of 5mv/°C from -1V to +3V. I was also able to correct for any length lead resistance to so only a 2 wire RTD is necessary. My boss was so shocked and excited he didn't wait for the lawyers in the patent department to do their jobs and immediately put my design into production. The patent lawyers came back and said they can't patent the design now because it is already in production and is now considered common knowledge! There went my patent stipend of $300 from my company. LOL
Instructions not clear enough. I've got my EEVBlog 121GW Multimeter stuck up my arse now. I'm off to A&E. Do you think my meter will still be in calibration after the nurses and doctors retrieve it?
I think I've seen some very cheap DMM (9205A or 830 series DMM) with "temperature" measurement. I don't think they have proper internal temperature sensor, they're just fixed offset voltage coupled with onboard LM358 dual op-amp to amplify those 41uV/C into something temperature reading. I suppose they're just offset it to standard normal room temperature from factory. I'll try to heat it up one day to test it, the meter is super cheap though, less that $10 shipped. My Texio DL-2060 (IIRC) 6 1/2 digit bench DMM will do temperature measurement with proper temperature probe adapter, i suppose they provide that relative room temperature measurement inside those adapter then compare it to the readings from plugged thermocouple/sensor, the meter does allow you to set whatever temperature offset that you want though (probably similar to REL function if you don't have the proper adapter).
Just note that some cheap-arse meters do not have cold junction compensation and just assume an average room temp of 25 degrees C. They'll just always measure 25 degrees C when shorted, no matter if ambient is cold or warm.
In my opinion, this feature is not useful, though mildly interesting for illustration purposes, I suppose. You demonstrated though your multiple example meters that this internal temperature measurement is only about +/-2degC at best. I can determine the ambient temperature (within a reasonable range, say 15-28degC) with that same uncertainty without any meter, and my estimates don't suffer from lag either.
I got one of the better Brymen multimeters since few years, but sadly it didn't have temperature reading... I had to buy a specialized temperature reader :/
I have a multimeter that came with a temp probe. I got it stuck out the window and I just turn the meter on when I want to know the temperature outside.
That's actually pretty freaky-deaky. Too bad only my multimeter doesn't have a temperature function but I'll keep this in mind for future upgrading. ;)
Nice one Dave! My Aneng AN8009 mesures it even without shorting the leads, afer a second of 0000. And indeed if you cool the multimeter down in the fridge, the thermocouple leads don't show the real ambient temperature anymore, it is suddenly same as internal, or thereabouts. Nice trick!
My BSIDE ADM66 multimeter gives me the temperature as soon as I set it to the temperature setting. I had never played with this setting before. I have another multimeter and I'm now curious to see if it also works in the same way. Thanks Dave.
I just noticed that my multimeter has this thermocouple temperature thingy. What is the purpose of it? Why would you need to measure temperature with a multimeter?
I’ve noticed this effect before however I always thought it had something to do with the contact between the two probes doing some magic, now that you mention the cold junction temperature compensation it all makes sense! However, I’ve just tried it on a Keithley DMM6500 bench DMM and it reports 22.80 °C (5 °C lower than ambient) right after power on, leaving it for a couple minutes to warm up shows no difference despite it clearly warming up on my thermal camera. I get the same results using either shorted probes or a proper ¾” shorting jumper? I pulled up the calibration report and it was calibrated at 22.2 °C, maybe the cold junction temperature is hardcoded or something but that wouldn't make sense? Edit: Just tried it with my old pile of garbage DIGITECH QM1323 and says 25.4 °C which is only 2 °C off but it does respond to temperature changes (very slowly).
Interesting, Will have to try my bench meters and maybe put them in the thermal chamber. There are different methods for doing the compensation, so could be something interesting happening here.
@@EEVblog I've just had a look through the manual for the DMM6500 as I don't use it for temperature measurements and it says the "Thermocouple Reference Junction" is 'simulated', I now see I can go into the UI and it's set to 23 °C! Changing it to anything else changes the shorted reading to that. It appears you can attach an external reference junction as part of the SCAN accessory cards.
@@WizardTim Wow, had no idea! But thinking about it, it makes sense, as rack mount gear can heat up, so an internal temp sensor isn't going to be at ambient temp for that absolute reference.
@@EEVblog This might make a good trap for young players video (or maybe as an addendum to this video?) as the K type thermocouples I have I always thought were bad because they measured way off on what I thought was the best tool I had for utilizing thermocouples! Turns out they’re all spot on!
Well, now I know that if I ever buy a multi-meter with a Temp Setting, I can use this trick, but until then, I suppose I will just make my own thermometer. (hah..more fun that way anyhow)
As a kid, I partnered with a guy who would solder mod chips into consoles. Two of us working meant we could mod twice the amount of consoles & we made a killing! Sometimes I'd watch him work, he was about 45 and would use an analogue multimeter, he said he'd bet his life on it being more accurate for everything and wouldn't let me touch the thing. I used a trusty UNI-T digital multimeter. Anybody prove/disprove his claim? Looked online & couldn't find an analogue meter today..
This fonction of that kind of multimeters is always far off. I even don't understand why this is implemented. Even in this video, no one give the same "ambient temperature" at one degree C !
My multimeter doesn't have a temperature function but i bought a temp prob anyway. Is there any formula to calculate the temperature based on the measured resistance? I know it's not practical but I wish I could do this
Hi Dave! Remember me? Yes, it's the spam your resume guy. Guess who just landed a job by spamming his resume? Absolutely no cover letter, I had no idea who I'm sending it to or what the company does, I just clicked the APPLY button and closed the tab. Today I had my test day and I'm bringing in my documents this Monday! And it couldn't have been any other way. And of course, the effort only comes after signing the papers. As always.
better yet tell us how to measure temp using the probe but with multimeter that does not have temp function. Like what ohms correspond to what degrees...
My Voltcraft meter does not seem to do this. It does have a temp function on the dial. Not that I need it. I have oodles of DHT22 sensors kicking around.
