Inside a diamond tester. (thermal conductivity)
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- เผยแพร่เมื่อ 9 ก.ย. 2024
- These are really common on eBay. For something so cheap the devices are surprisingly sophisticated.
Any thoughts on the probe material and function?
If you enjoy these videos you can help support the channel with a dollar for coffee, cookies and random gadgets for disassembly at:-
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I love it when he gets surprised and excited seeing things he did not expect.
Isn't that the real joy in anything though? :)
Endearing how excited he gets over discovering a PTC thermistor! Great stuff
Me too.
Clive got his own Super-Bowl ring. {0.o}
I watch a lot of reviews on TH-cam to hear about how bad something is. But I really enjoy it when Clive finds something that he likes.
Clive is the REAL diamond!!
Ok
So looks like it has two back-to-back thermocouples, so at a constant temp the voltages will cancel out. The output will be in the microvolts range, so the pot will be to cancel out the input offset & drift of the amplifier stage - there will also be some thermocouple effects on the PCB & components so it would be pretty hard to make something like this without a manual offset adjustment.
mikeselectricstuff in that sense is it like a PIR or load cell where the actual values mean less than the fact there's a differential?
Mike ya legend!
Cheers for the breakdown there...
...and make some more vids, ya legend!
Thermocouples work by welding two dissimilar metals together. based on what I can see in the video and confirmed by Clive, the joints are soldered together. soldered joints will not make a proper thermocouple.
I would say, they are using a resistor bridge. the PTC wire is the common and the 2 copper wires are the other two ends of the resistors. the rod is the resistive element and it would have low thermal conductivity I would guess something like stainless steel (although, stainless doesn't take solder as far as I know)
RTD?
I also think that soldering two metals together will not make a proper thermocouple.
My mate designed this and the Chinese brought him out.I have one and he said they stuffed it up, he still has the one that you calibrate ..The metal channel shows the different caret size and how to set it ..He is 91 now and is still as sharp as a tac..
@John doeHe is 90 plus now and has had a plentiful life .He was a very smart man.
I have one because I by scrap silver and other jewelry, very useful for a cheap tester, little tricky to et a hang of but once you do you can check dozens of similar sized stones really quickly once everything is set.
Sounds to me that it might work like a hot-wire anemometer for measuring air speeds. The thermocouples control the current flowing through the wire to maintain some temperature. By measuring the change in current to maintain that temperature you can estimate the thermal conductivity of whatever material you touch the tip to.
Always wanted to see the inside of one of these!
A simple method is to hold the stone to your lip. If it feels cold like metal, then it is likely to be a diamond. Other gemstones feel warm as they are not highly thermally conductive. The synthetic gem he mentions "moissanite" has a lower density, a higher refractive index and a slightly lower hardness than diamond. However, moissanite is electrically conductive while diamond is an excellent insulator. I'm sure Big Clive could whisk up a suitable detector for it!
damn moisanites are pretty awesome actually ... the colors they make when you shine a bright light on are simply stunning
Any metal can be used as a "thermocouple" if you don't care about the actual temperature. As in this case, the rate of temperature change from one end of the rod to the other is all we are concerned with. The principal of the thermocouple relies on the material(s) Seebeck coefficient. Not an expert on this, but basically any metal develops a voltage difference from one end to the other due to the temperature difference. In a true thermocouple two different known materials are used (usually with Seebeck coefficients of opposite polarities - so the generated voltage at the ends is maximized). In this case, since we don't really care about accuracy or the actual temperature, you can get by with one rod (the wire makes up the second leg of the thermocouple in this case) and the device just registers the change in voltage (or the rate of change) due to the temperature difference along its length. As long as the wire and the rod have different Seebeck coefficients the temperature change will cause a voltage change. That's my theory anyway.
It has to be a junction of two dissimilar metals.
The junction of dissimilar metals is there so you can measure the voltage from outside of the sensing location. If there was some magical way to measure the voltage at both ends of one piece of metal without a second lead wire going to the hot end, then you could make a thermocouple out of one material. The fact that you need a conductor to measure voltage is why you have the second material. It is a dissimilar material so that it has a different Seebeck coefficient. If they had the same Seebeck coefficient the generated voltages on each leg would cancel each other out.
In this case the second leg is just the varnished copper wire.
the metals are soldered together, that's not how you make a thermocouple
Agreed: Not how you make a thermocouple. But if all you need to do is measure a temperature change (as measured by a voltage change), then you could use bubble gum to attach the leads.
I agree that the joint does not have to be mechanically sound, even a twisted wire would do. but when wires are soldered, by definition, the solder metal makes the interface between the two metals. the two metals don't come in direct contact. I don't think that would work properly
The heatsink thing and the anodization is fascinating.
When I saw the ring, I thought you had John McCririck as a guest star!
hehe underrated comment!
Clive, at times I wonder if you're self-aware of the calming quality of your voice and your channel. Given how gingerly you removed the tester from the package I think you are.
There are viral videos going around where people go to malls and other public places and challenge people to test their jewelry to see if it's real diamonds. Occasionally the host will adjust the dial a bit and I think he's upping the sensitivity when he thinks the person is confident and doesn't want to make them mad. It also obviously has the issue of not being able to test for moissanite.
At (5:35): Aluminium oxide is a actually a good thermal conductor. Treating the aluminium (anodizing) makes the surface quite porous and hard. For aluminium to air conductivity that might even be a plus due to the larger surface.
I’d assume that the tip of the tool can’t get a good conductivity with the anodized material as it it quite hard and porous. Bare aluminium is quite malleable and might form a nicer surface and hence better conductivity. There will be a thin oxide layer on these patches too, but I thickness and porosity might be significantly less.
I would say the hardness scale you mentioned is for scratch resistance.
I read that the glass of my watch has a resistance of 9 (sapphire glass) and it is probably not nearly as hard as diamond.
Instead of using the thermocouple effect, maybe they're measuring the resistance of the sampling rod. The PTC has a power and ground side. The ground of the PTC is used as the common for measuring the resistance at the ends. It doesn't have to be absolutely precise but would need to have both ends balanced like a wheatstone bridge. Easy job for an op-amp and eliminates the non-measuring connections from forming an accidental thermocouple.
Yes I was thinking the same thing, I believe it's more than likely.
Could be a "Type T" thermocouple.
If true, the wires are just plain copper and the rod is constantan. The two junctions would generate about 43µV per °C temperature difference...
ooooh, constantan. Bring me tapas!
So this thing works almost exactly like a Mass Air Flow sensor in a car intake, except instead of pressing the tip against a gemstone the tip is in the intake air stream and the other end is protected from airflow. Higher air pressure cools it faster, more airflow cools it faster, and the ECU can accurately calculate, from that, the absolute amount of air going into the engine at a given time.
IMO. Diamonds have more industrial appeal than aesthetic.
that mic bass boom makes u sound like bloody barry white
Sean Connery
I LOVE THAT
The Walrus of Lurve ...
Apple > Android
@@qwertykeyboard5901 no it's not 🍏💩
I love the joy and excitement when he finds the PTC.
There's a make-on-demand engagement jewellery store in western Canada (Spence Diamonds in Edmonton, Alberta to be specific) selling synthetic, gem-quality diamonds in their custom engagement rings. Of course, they're still trying to market them as "Artisan Created Diamonds" and play up their 'rarest diamonds in the world' status (they have exclusivity contracts with their supplier, I think). They also insist that they're "the same cut, colour, clarity, and price" as a natural diamond, "just 20% bigger" (which is a silly way of hiding the price difference), and back them with an exchange policy for (smaller) natural diamonds. Marketing at its finest, and I've got to wonder how much their markups are. Still, even though moissanite obsoleted diamond for jewellery, I'm excited for the time when synthetic diamond gets cheap enough and large enough for useful consumer products (heatsinks, lenses, etc.). And of course the death of DeBeers, if of course those scumbags don't pivot to another scam.
Should test it out on the crown
I really like the 'out-loud' thinking.
Would you mind trying that gizmo on some metals? I wonder if it can be used to differentiate between aluminum and pot/zinc metals or help classify bronze/brass alloys either directly or watching the 'swing' of the meter. A quick non-destructive method to classify metals or alloys would make picking the right weld/braze method or filler a lot easier.
Could be 2 type T thermocouples... that would kinda work with the colour code too. The white lead would be Constantan (copper nickel alloy) and the other lead would be copper. It is also a fairly low range type of thermocouple so that would increase the accuracy of the device.
Matthew Clitheroe There's no measurement wire connected to the middle (needle) material. The two copper-needle thermocouples are connected backwards in series so the average temperature cancels out and the difference is doubled. The connection between the two thermocouples is simply the rod itself. The two white wires power the little heating element. Touching metal is detected by electrical measurements between the tip (via one or both copper wires) and ground (via the metal plate). Heating up is detected either with a fixed time delay or by checking the current through the PTC heater.
The two thermocouples are the same basic idea as a "Mass flow meter" the basis for "Mass flow controllers" (feedback to control a valve position to control flow). The ptc being a heat source instead of a hot wire being cooled and temp being measured up and down wind. Cute design. Tootles... Wade
you could check it on a dressing diamond used in a grinding disc dresser. Alternatively, a diamond in a glass cutter tool could help testing it too. The differential temperature measurment method with a heater centered between 2 thermocouple sensors is also used on a pipe in mass flow meters of gasses and liquids.
Mining permits are close to being approved for areas around Mt. St. Helens. One of the minerals of interest is diamonds.
I'd be interested to see if you got a different reading on a heatsink with thermal paste.
The reason anodising is beneficial to heatsinks is because it creates a microscopically porous layer which effectively increases the surface area, and hence improves dissipation. However because the surface is less smooth, it has less area in contact with the heat source. Thermal paste increases this area by filling the pores in the anodised surface, which improves thermal conductivity, so I'm guessing we'd see a bit of a difference using this on a heatsink with thermal paste.
The pores are in the 100A to 300A range, very small and once died black and sealed in boiling DI water it is no longer porous. In early days you hard anodized a heat sink with a thick layer to act as an insulator so your didn't need a mica insulator. Wouldn't do any good to have more surface area on the heat sink then on the device in any case.
What is the reason for adding a mica insulator on heatsink?
So when the next time i see a heatsink anodized on the part which interfaces with the heat source i can presume that whoever designed that device have no idea what the fuck they are doing?
If the body of the component attached isn't at the same potential as the heat sink, typically ground/0V, or the potential of other components attached to the same heat sink,the mica isolates the component electrically from the heat sink and/or other component[s]. See also sil-pad.
Wonders will never cease. I arrived at the conclusion about measuring temp differential at the same time as you said it, congratulations on pushing knowledge into this slumbering brain "I is lurning"
Interesting on how much work has gone into designing and manufacturing for less than a £10
Always a joy to see a new Bigclivedotcom video....just a wee bit of disappointment when he doesn't have a chance to say, "fresh, juicy, lead-based solder." Still, fun to watch and I learn stuff.
My friend, who is a jeweler from a family of jewelers, has enough experience to sense the thermal conductivity of a legitimate diamond by touching it to his lips. (You pointed out the ceramic oscillator; I believe my Arduino has a crystal oscillator for the USB timing and a ceramic oscillator for the processor.)
Don't you hate it when just at the moment you decide to go to bed, you get an notification for a new bigclive video ?
:-D
MusicalBox actually I like his videos at bedtime cause they help me relax enough to fall asleep. :)
If the sensor is a thermocouple junction then my guess is that the device sends a current through the junction (causing it to heat). When temperature stable, the current is at a minimum (ambient loss). If heat is drawn out of the hot end then current will increase. The op-amp may be used as a precise current sensor allowing the current change to be measured. Change in current would relate in some way to the thermal resistance of the test material.
- Eddy
That bass boost makes you sound like the love child of Brian Blessed and Sean Connery.
That is really interesting on the heat conductivity of the anodized layer.
I was under the impression that thermocouples needed a fused junction of the two metals. these are soldered as you mentioned.
I would say it's a resistor bridge. the rod is a low conductivity metal, the ptc wire is the common point and the copper wires are the other ends of each resistor.
Fusion not needed, twisted wires will do for temporary service. Introducing a third alloy (solder) muddles things, except in the case, as here, where the same solder is used on both junctions.
Brilliant video as always Clive!
The solution of course is to consciously wear moissanite instead of diamond.
Why overpay when the moissanite is sparklier anyway?
I'd like to test some desktop thermal compound called IC Diamond which I believe may have diamond powder in for heat conduction between the CPU and heatsink
If i understand the device correctly it would 100% give you a false positive no matter which thermal paste you use
I just bought tester at amazon came with battery 9v and lasted 3 days now i have to go by a pack of 9v of duracell or energizer batteries
Wow Clive your ring has more sparkle than liberaces
Also the anodization of the heat sink is a big discussion in computer heatsinks company’s have spent millions on making a coating that isn’t worse than bare aluminum.
Cheers Clive, diamonds should be only used for abrasives.
Yeah my girlfriend was pretty abrasive till I gave her a diamond.
I’ve seen black light (UV) used to tell if diamonds are real as well.
It might be a pair of type T thermocouples, made from Copper/Constantan. These are sometimes connected back to back to measure temperature difference. The higher thermal conductivity of copper will also help in sinking heat to the tip. Another advantage of type T is that the lead out wires can be made of copper.
AndyP, I'd bet they went even cheaper and used extension grade constantin (u-type) wire. Good to 150C and they can just use tiny copper bell wires to form the junctions. They don't even have to do any research since the mV for the range is published even in such an impure grade of constantin.
Yes, I bet that is the cheaper extension grade, the accuracy is probably good enough for looking at large conductivity changes.
2:35 The manual says " Diamond Selecter II" but the device itself says " Diamond Selector II."
So which is it?
Selecter is the "Chinglish" translation of the English word, _*selector*_.
Could be useful as a "Heatsink Tester"! I could always test this on the Wife's ear-rings (which are "the Real Deal") . . . . .
Phil S, it only tests conductivity to the heat sink, this just depends on the material used. Any block of aluminum will be the same to it. The important heat sink property is the dissipation rate once its warm. This will be far too slow for this tester, and the tester is also too light to heat up most heat sinks.
@Sander Deryckere, no, that wasn't the problem he was thinking, the problem was to test whether a heatsink absorb heat or not (like in the video)... turn out that the heatsink in the video failed a heat conduction test because of its coating; it is unable to conduct heat from its surface (or to its surface) unless if the coating is scratched away.
xponen But according to Sander that anodization effect is more important during changes in heat output (measured by the Diamond tester) than during a steady state situation (when a device produces 50W that needs to be continuously removed.
That’s why these are normally sold in pairs with the moissanite detector that looks identical but tests for electrical conductivity rather than heat....
One of the few channels I would never regret subscribing to it.
For those of you who have noticed yes I am going to build a bomb using this knowledge lol ... (The last lol is for our big brother in the NSA) ...
FBI OPEN UP!
Anodized aluminum has a thick layer of aluminum oxide (alumina) which is electrically and thermally a non-conductor.
It looks almost like a voltage divider for temperature. It measures the thermal drop across the piece of wire just like a resistor for voltage.
Clive, have you seen the febreze alternating dual scent air fresheners? Looking through the vents, there’s a circuit board inside with two large resistors and a capacitor. Wonder what’s doing the timing. The assembly is heat staked shut.
They tend to use a blob based microcontroller with simple support circuitry for power and to switch thyristors for the heating elements. I took apart a three channel version:- th-cam.com/video/cG8tLyJDQbk/w-d-xo.html
Is it as good as Diamonique Diamonds, I wonder if you rubbed some Artic Silver on to that micro-controller and rub it off and see if the numbers appear so you can ID that micro-controller.
in the past many times the number was also on the bottom of the chip although I havent seen that lately, Also I have been able to resurrect the part number using a high power magnification and able to see the remnants of the original number
Zirconium encrusted tweezers....thinking of you Uncle Frank(Zappa)💎💎💎💎💎👍
Diamond prices are highly inflated by De Beers. Ask any Geologist you know... In fact most Geologists hates diamonds to the point most of them don't even use them in their wedding rings.
Cool Beans. I was thinking they used Electrical Conductivity. Thermo Couple generate Current not so much voltage variations. They're measuring the current variance. Bet the Op AMP is set up in a Differential configuration ?
So what you really have is a thermal conduction tester for your heat sink. Q&D (quick and dirty ) for R & D!
Fascinating video, thank you.
Computer heatsinks are never anodized, because the process replaces Aluminum atoms with an element that can bond in the same way, im imagining any element with the same number of electrons in the relevant electron shell, which would be 3 if Im not mistaken.
Youd have a whole surface layer of poorly conducting material.
Thank you so much for this video. My Mom has had suspicions about her jeweler before, but we didn't really know how we could begin to validate that her gemstones were still intact. Super helpful knowing how these testers work, and thus knowing how someone could fake a reading if they wished.
Was the move "Lock Stock and 2 Loaded Barrels" or "Snatched"?
Most people use these to check that the watch they've just bought does indeed have a sapphire crystal like the seller said it did.
The clip would have been even more interesting if there had been a comparison between regular glass and sapphire watch crystal. Many people use these to distinguish between mineral and sapphire watch crystals.
I like gizmo's like this and love to know how they work. Thanks for that Clive. I like your videos and have watched most of them.
This one looks a lot better inside the one I got from China a while back. That one had a jumble of components thrown in, also did not work correctly.
How does it detect when you are touching metal? That triangle plate on the cover doesn't seem to be connected to anything. It looks like it should be connected via a spring on to the PCB through the round hole in the plastic but I didn't see any contact pads or springs on the board.
+MrMaxeemum There is a wire connected to it next to the piezoelectric disk.
Since the tip also generated heat, is it possible that the two copper wires are used to pass a mild current through the rod and thus heat it to 36.3C? The thermistor would then monitor rate of thermal conduction out of the rod. Possible?
yes people are over complicating it.
I wonder if it is a thermocouple. You said it needed to warm up to 36C. That implies a heater in the tip. I suspect that the probe wire is nichrome or the like and the two hunks of magnet wire put a current across it. The thermistor then sees a change when you touch the end of the wire to something cold. Perhaps somewhat like a hot wire anemometer.
BTW, you didn't comment on the trimpot at the back of the board.
The round component is a PTC thermistor. It's a self regulating heater.
I'd guess the trimmer is for calibrating the range of the sensor.
Are you sure it's a thermocouple arrangement (using the Seebeck effect?) Could it be just a 4-wire sensing arrangement? The current flows through the white wires, but voltage is measured across the enameled wire... I guess that the voltage drop of such short sections of wire wouldn't be high, but the fluctuations in temperature are probably very small...
personally maybe the op amp is use to GAIN the signal as the differential of thermal conductivity is so LOW, that the micro controller attached now can read the signal and have a range of frequencies(1-3 now have 1-100)(micro controller probably) at set up as a pontentiometer( were you can adjust a starting point[calibration]) at that given value, you set the micrometer to reals required voltage to the graphical display hence the manual calibration. to find their"zero poiint"....fr i work with thermoucple all day at work..i thought it would have been a lux sensor in that thing :L
Love how the calibration dial is also the volume dial 😅
Yeah you did! That and a few helpful comments in the "below" explained most of my questions about this device!
So if i got it right this device is pretty much useless to test larger uncut gemstones. Especially those embedded in ore rock?
The simplest answer is usually the solution - especially when you're talking cheap stuff. Constant current supplied by the two copper wires heats the rod to a set temperature. Thermistor in the middle detects temp, and dial sets it to the middle. Constant current means constant temp for set resistance in a set environment. You zero the graph, and anything you touch the tip to drops the temperature, moving the graph. Just a guess, but I find it hard to believe they'd have balanced thermocouples at that price.
Occam's Razor demonstrated. Congratulations, you guessed correctly!
Thanks Clive
I could be wrong but I was told to blow on it and if it mists over it’s glass and if it doesn’t it’s a diamond.
mavos1211 Only works in certain atmospheric conditions, but same principle as this device.
Time for a long mining session to find those diamonds
The white wires will probably provide the current for the heating
3 of each color led? Just how much did you have to drink before making this??? There are 4 of each color led
I was starting to wonder the same thing... :P
THERE. ARE. FOUR. LIGHTS!
monotonehell Jean Luc ??
They should include a real diamond to calibrate it on. :-)
I own that one you are inspecting so I was interested in how it works myself. But without damaging it since I only used it 2 times and like to in future. If it legitimately works. Thanks!
Cleves got drip guys
Jewelry isn't supposed to sparkle. That is the easiest way to tell if it's fake. Silver, gold, diamonds, not one is supposed to be "glittery" in anyway/
How do the dilithium crystals stayed cooled?? Oh, they dont. That's intuguing . Awesome dude.
Are the big stones (more then 50 0r 100 gram) may tested through this tester
nice tip about the heatsink though
I suspect the chip just drives the bar graph and the clever bit is just a wheatstone bridge
also...be careful not to "touch cloth" !!!
It's not that critical which materials they are; any two different materials usually will exhibit the Seebeck effect.
Did I miss the part about the metal plate on the back? The metal plate and the 'tip' could also be a second input channel. Is it connected to one side of the PTC so that a human body becomes a paralleled component across the PTC? Would the human body affect the resistance or the inductance?
+Jay Herde it's the electrode that detects when you miss a gemstone
And touch the probe to the metal.
Might it be something like a four wire Kelvin measurement device?
It might be Trididdlium Fartoxide or Pentapoxylose Dispunkide
In reality, they make great door stops
Just read some interesting comments there and it seems the the secret is in that unidentified chip.
Why didnt you test it on a diamond?