*Section* This video showcases a thermogravimetric analyzer, a highly precise balance used in materials science, particularly in high-temperature corrosion studies. * *[**0:00**]* *High Precision:* The instrument can detect minuscule weight changes, even on the microgram level. It boasts superior precision, accuracy, and resolution compared to traditional load cells. * *[**0:35**]* *How it Works:* * *Balance Arm:* A delicate balance arm holds the sample on one side and counterweights on the other. A torsion line allows for minute movements. * *Electromagnetic Control:* Four solenoids (electromagnetic coils) exert force on the balance arm, keeping it centered. * *Optical Sensor:* A light source, a slit plate attached to the arm, and two photodiodes act as a feedback mechanism. The amount of light reaching each photodiode indicates the arm's position. * *Current Measurement:* The current flowing through the solenoids is proportional to the weight difference, allowing for precise weight measurements. * *[**19:41**]* *Calibration:* The instrument needs to be calibrated using known weights to correlate current with weight. * *[**36:36**]* *Applications:* The video demonstrates the working principle of the balance, highlighting its sensitivity. Potential applications include measuring weight changes due to oxidation or evaporation. i used gemini 1.5 pro to summarize the transcript
@wolpumba4099
Ай бұрын
It is not entirely clear to me why two photodiodes are used. This is the reason gemini came up with: Two photodiodes create a *differential measurement*, making the system more accurate and stable: * *Ambient light fluctuations* and *light source variations* affect both photodiodes equally, canceling out their impact on the difference between the photocurrents. *The difference is likely measured using an op-amp:* 1. A resistor converts the photodiodes' current to a voltage. 2. A differential amplifier, using an op-amp, compares the voltage across each photodiode, outputting a signal proportional to the difference (and thus, the balance arm's position).
@CuriousScientist
Ай бұрын
@@wolpumba4099 Hey! Thanks for the executive summary again! I will look into this other way of getting an output signal from the photodetector. As far as I understood, they just act as two current sources and due to their connection, there will be a resulting net current which is then proportional to the distribution of the incident light between the two photodiodes. I could be wrong. I will dive deeper in the near future so I can learn more about it and understand it 100%.
@noanyobiseniss7462
Ай бұрын
Algo time.
@CuriousScientist
Ай бұрын
Much appreciated!
@DaveEtchells
Ай бұрын
Fascinating mechanism, the general concept is very similar to an idea I came up with for a balance to detect very small changes in weight (1mg or less) as water evaporated from an object weighing up to a couple of Kg. I had been thinking of an LVDT displacement sensor to detect deflection of the balance beam, but the photodiodes are a much simpler and entirely adequate approach, since we don’t care about measuring the displacement, just detecting the null position. I’m a little surprised that this system doesn’t have something like a magnetic eddy current damper to dampen oscillations, though; doesn’t it tend to want to oscillate a lot, or is there in fact a damper somewhere? One thing I’m not quite understanding is how the arrangement of coils works to control the net force on the beam assembly. Solenoids usually just pull their core into the coil as current flows, but here the same current is flowing through all four coils, so it seems like the arm position should be unstable on either side of the null position. (As more of the cores’ material gets pulled into the coil, the force on it should increase, while the force acting on the opposite core should decrease.) I imagine it has something to do with the magnetic moments being induced in the two sides of each metal slug by the opposing coils being opposite to each other and that somehow resulting in a net force one way or the other (?) I can’t quite get my head around it. Thanks for sharing, if I ever get around to the experiment I wanted the super-sensitive beam balance for, I now know a better way to do it. 👍😁
@CuriousScientist
Ай бұрын
Hi! Yes, it is indeed an amazing instrument. Your idea also sounds interesting! Regarding the damper, I think the system just dampens itself, there is no external dampener. When you use this machine, you anyway need to wait quite a lot for the relaxation. The coils don't produce the same magnetic field when it comes to their orientation. They are connected in a way that some are N-S and some are S-N magnetized. So their polarity is not identical. I don't remember the exact sequence, but in the video, I show how the wiring of the coil is done, so you can trace it back from there. If needed, I can somehow demonstrate it in an upcoming video. I came up with an idea to make my own calibration weights, so I might make another video on this device in the near future.
@DaveEtchells
Ай бұрын
@@CuriousScientist Thanks for the reply! Yeah, I got that the coils are wound in opposite directions but couldn't quite grasp what the net consequence of that was, such that the system wouldn't be unstable away from null. I need to look at that section of the video again and think it through a little bit. Looking forward to what you might do with the balance, and just how sensitive it is. You mentioned micrograms, I wonder just what it's resolving limit would be?
@CuriousScientist
Ай бұрын
I unfortunately don't know its resolving limit. I will try to dig up some handbooks or manuals from the internet, or ask some colleagues at work, but I honestly have no idea. It is just an informed guess based on similar equipment, but these things can resolve below the microgram level. They are insanely sensitive.
@victoribarra9930
Ай бұрын
As always. Excelent video! Thanks. Have you used a TGA before? If not. You do need to input the weight of the pan with the sample. So you need a balance to get the weight before. I guess you calibrate it when you input the weight. If I don’t recall it wrong there is a limit on pan+sample weight. Now I know that it may be because at certain limit you won’t be able to compensate your sample with the instrument’s counter balance. Still getting a calibrated weight standard that size could be troublesome. The interesting think is . How this thing measures weight when there is turbulence, such as that when water starts boiling?
@DaveEtchells
Ай бұрын
@@CuriousScientist Yeah, I wouldn’t be at all surprised if it were micrograms or even less, given the setup. You’ll probably be able to get some idea if you can get a milligram weight to test it with; get it nulled and then put a mg on one side and see how much change in current it takes to null it back again. I had a thought for poor man’s milligram-level weights: I haven’t run the numbers but if you have any very fine magnet wire or resistance wire, you could calculate the weight per unit length based on the diameter and density of the material and probably come up with milligram-level weights from not-impossibly-short pieces of the wire. The enamel on magnet wire would have a non-zero impact, but it’d be much less dense than the copper, and/or you might be able to strip it with some sort of chemical or possibly just by getting it really hot and then wiping it away with a tissue. (pause) - So I just asked ChatGPT to do some calculations for me 🙂 As an example, #36 magnet wire has a diameter of 0.005 inches. Based on the density of copper, it would weigh 1.14 mg per cm of length. Typical "single build" enamel insluation is about 10 um thick, and if it had the same density as plexiglass, it would add about 4.5% to the weight of the wire. (Double-build insulation is twice the thickness, so would contribute twice the weight. It's used in high-voltage or high-reliability applications, but single-build is apparently much more common.) This would only be helpful if you happen to have some super-fine magnet wire laying around, but I figured that might be more easily come by than milligram-level weights 🙂
@aleksandarsentice3028
Ай бұрын
Is that pointer heating element from soldering iron? Thanks for the nice presentation and in depth explanations.
@CuriousScientist
Ай бұрын
Hi! You have super sharp eyes! It is indeed a tip for my T12 soldering station. 😄 I just found it convenient to use it as a pointer.
@paulpease1788
Ай бұрын
If you removed the tiny air conditioner from a countertop ice maker could you add a reversing valve and use it as a heat pump? Sorry wrong video
@CuriousScientist
Ай бұрын
I don't know, especially because I have never seen an ice maker from the inside. Also, I have no idea where (and why) there is an air conditioner inside it. I thought it is just a freezer. BTW, I have Instagram, Patreon, and also an email address where you can send me messages which are not related to videos but you still want answers. Cheers!
@t1d100
Ай бұрын
👍👍👍👍👍
@CuriousScientist
Ай бұрын
👋👍
@stevenbliss989
Ай бұрын
Load cells by nature are not so accurate, but they are CHEAP!
@CuriousScientist
Ай бұрын
Depends on what kind of load cells. The ones I work with at my job are super expensive.
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