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Measuring temperature of aluminium ring


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So we are conducting a experiment with the Leidenfrost effect. We are trying to generate energy using this phenomenom. The leidenfrost effect occures whenever the temperature of the heated surface gets to around 210 degrees celsius. Reaching this exact temperature is important for the experiment. We thought about using a IR thermometer. But soon found out that because of the emissivity of Aluminium it wouldn't work. So we started to think about other ways to measure the temperature. We still haven't found a solution to this, but have come up to an idea. We thought painting the Aluminium Leidenfrost ring with some kind of black paint which an high conductance. What kind of paint or would anything else be better to determine the temperature of the ring. Any help is appreciated and sorry for any spelling mistakes made since I don''t speak English very well.

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38 minutes ago, RaytjeKn said:

So we are conducting a experiment with the Leidenfrost effect. We are trying to generate energy using this phenomenom. The leidenfrost effect occures whenever the temperature of the heated surface gets to around 210 degrees celsius. Reaching this exact temperature is important for the experiment. We thought about using a IR thermometer. But soon found out that because of the emissivity of Aluminium it wouldn't work. So we started to think about other ways to measure the temperature. We still haven't found a solution to this, but have come up to an idea. We thought painting the Aluminium Leidenfrost ring with some kind of black paint which an high conductance. What kind of paint or would anything else be better to determine the temperature of the ring. Any help is appreciated and sorry for any spelling mistakes made since I don''t speak English very well.

Can you not cement a small RTD (resistance temperature detector) to the ring and set up a suitable measuring bridge ?

https://en.wikipedia.org/wiki/Resistance_thermometer

You have given no idea how big the ring is so I can't be more detailed.

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55 minutes ago, RaytjeKn said:

Thanks for the fast reply. The ring is 400mm in diameter. How would we doing this exactly? This RTD is new for me so I don't exactly know what to do.

 

It's all there in the Wiki link I gave - just copy and paste it into your browser.

You could also use a thermistor, but as many of these are restricted to 150oC amd most to 200oC you would have to look for one of the 300oC ones.

Since you are operating at around 210oC you have a narrow temperature range and either device will be sensibly linear over say 190oC to 220oC.

I would suggest four sensors, spaced around the ring at 90o intervals.

 

Edited by studiot
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38 minutes ago, RaytjeKn said:

Would putting the thermistor circle on the surface give an accurate temperature? Seems like I would have to calibrate the sensors. But calibrating them would make me have to measure the temperature again.

I hope you are not seriously suggesting you intend to perform a scientific experiment, without calibrating your equipment?

Thank you for the picture, but your posts are still very short of details here.
For instance what is project for ? (I know it is " So we are conducting a experiment with the Leidenfrost effect. We are trying to generate energy using this phenomenom ") but is this coursework, collegework or what?
You don't say anything about how you are going to heat your aluminium ring.

To calibrate you could put it into a thermostatically controlled oven (perhaps with an oven thermometer as well) and calibrate that way, before the actual experiment?

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Okay I'l start from beginning to finish. I am with a friend of mine conducting an experiment with the Leidenfrost effect for our graduate year. Our goal is to create a system which is able to generate electrical energy using the Leidenfrost effect. Our setup looks like following: We have an electrical plate which heats up the ring, the plate is not capable of using a certain temperature. On the plate we put the Leidenfrost ring, with water in it of course, on top of that a little alluminium circle with holds 4 magnets which generates energy using the Lorentzforce. But when conducting this the Leidenfrost ring has to have a precise temperature to work correctly. This temperature is 210 degrees celsius. We thought we could just use a IR thermometer but these apparently don't work all to well with aluminium because of the emissivity. So now we are looking for a way to measure this temperature with an easy as possible way. Our budget is not crazy big and our knowledge about physics also isn't all too good. We know the basics and we are trying to accomplish our goals. Sorry for not being too clear about it and I hope this helps. My English is not all too good. 

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1 hour ago, RaytjeKn said:

Okay I'l start from beginning to finish. I am with a friend of mine conducting an experiment with the Leidenfrost effect for our graduate year. Our goal is to create a system which is able to generate electrical energy using the Leidenfrost effect. Our setup looks like following: We have an electrical plate which heats up the ring, the plate is not capable of using a certain temperature. On the plate we put the Leidenfrost ring, with water in it of course, on top of that a little alluminium circle with holds 4 magnets which generates energy using the Lorentzforce. But when conducting this the Leidenfrost ring has to have a precise temperature to work correctly. This temperature is 210 degrees celsius. We thought we could just use a IR thermometer but these apparently don't work all to well with aluminium because of the emissivity. So now we are looking for a way to measure this temperature with an easy as possible way. Our budget is not crazy big and our knowledge about physics also isn't all too good. We know the basics and we are trying to accomplish our goals. Sorry for not being too clear about it and I hope this helps. My English is not all too good. 

Thanks.

I have asked for guidance as to how much help to offer, but here are some thoughts.

1) Many industrial/commercial companies, large and small, need a temperture controlled oven. For example a local potter. Try family connections or befriending one to use one for a couple of hours.

2) I use this cook's kitchen thermometer to make bread. But it does cover the rage you require.

cookstherm.thumb.jpg.7850b25e8edd4ff9284e2793d33dea52.jpg

 

These are incredibky cheap.

Obtain one and temproarily mount it on your ring as follows.

Obtain a block of aluminium or copper with a large flat face
Drill a hole into it, say 75mm deep so that the metal prong of the thermometer just slides in.
Obtain some thermal heatsink compound/ grease from an electronics supplier (again very cheap)
Smear this grease onto the probe for the insertion depth ad fit it tightly to the hole in your block.
The probe (now mounted in the block) should then be able to be supported sticking out sideways past the edge of your ring so you can read the probe and it is not affected by the hotplate.
Clamp, screw down the block to a flat surface on the ring, again using thermal grease.

Now you can make your calibration manually reading the thermometer.

The thermal grease is a standard electronic part for aiding heat transfer between hot components (power transistors etc) and their heatsink in electronics.

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Okey this is exactly what I was looking for. I really see where you trying to get this. But just to make everything a lot more clear I have some pictures. You say a hole of 75mm deep. I think you mean 7.5mm deep because the ring is only 4cm wide and like 1.5cm high. The images don't include the object supporting the thermometer on the right side. I'm not 100% sure this will work as you can see in the 3rd image, the ring is split into two pieces. I can't use the top of the ring because there will be an aluminum thin circle plate on top of the whole ring (with the same 4cm diameter). I guess I can drill trough the two parts together and see if that would work. Hopefully this is clear.  

 

1.png

2.png

3.jpg

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4 minutes ago, RaytjeKn said:

Whoops my fault. It's supposed to be 40mm (4cm).

How thick is the sidewall of the ring?

The probe on my thermometer is about 150 mm long and the bit in the photo is on the end so I don't think a horizontal hole in the sidewall will hold it or enable a proper measurement.
You might be able to dill down vertically enough though.

 

I can't see you will have enough control with your hotplate heater to control the temperature well enough.
That is where a small sensor (the thermometer has quite a long thermal inertia) wouls be useful to control the power to the hotplate.

What subject is this project in?

Do you have a project supervisor, I think you have enough to talk to him or her about it now ?

It will be interesting to learn how you propose to convert this to electricity.

 

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13 minutes ago, studiot said:

How thick is the sidewall of the ring?

The probe on my thermometer is about 150 mm long and the bit in the photo is on the end so I don't think a horizontal hole in the sidewall will hold it or enable a proper measurement.
You might be able to dill down vertically enough though.

 

I can't see you will have enough control with your hotplate heater to control the temperature well enough.
That is where a small sensor (the thermometer has quite a long thermal inertia) wouls be useful to control the power to the hotplate.

What subject is this project in?

Do you have a project supervisor, I think you have enough to talk to him or her about it now ?

Well Like you can see on the third image the ring is split up in two parts. But I think I would quite easily be able to drill a hole all the way through the ring if needed (which means like 40mm deep). When the thermometer sticks out to the side whe could support it with something like a wooden block for example. I do have a supervisor, but he doesn't know much about the practical side of this stuff since he just studied physics, but even if he would know, he is not able to provide us with enough time to get this done. 

Indeed a smaller sensor to me would seem better. But all those RTD, NTC etc. seem a little complicated to me. I can order a RTD, but what exactly am I supposed to do with em. Take this one for example:  https://www.te.com/global-en/product-NB-PTCO-160.html or this ptc: https://www.reichelt.nl/ntc-weerstand-32-mw-10-kohm-epc-b57550g1103-p240079.html?&trstct=pol_7. Most of em offer a max temperature way over 210 degrees celsius so that won't be a problem. I know I can use the graph provided by the manufacturer to see what resistance belongs to what temperature that's not the problem. But I don't really understand how to place the RTD. The same way like the probe thermometer, or just put it on the surface also with thermal paste?  

We are working on some literature about how to conduct all this and if this way of generating energy could be used in our world or outer space. If you are interested we could show it.

Also like you can see in the video you provided. The guy is using a IR thermometer and a black block underneith the ring to measure the temperature. But I was told this doesn't give you an exact temperature reading. We really want to get the most accurate possible reading. Thanks again for helping. We really appreciate it!

Edited by RaytjeKn
Just saw a sentence I forgot to read.
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2 hours ago, studiot said:

Obtain a block of aluminium or copper with a large flat face

 

The purpose of the large block is to make sure it is at a common temperature with Leidenfrost ring.
That also allows it to offer support for the thermometer.
You may need to scratch your head a bit to work out a suitable shape to fit to the ring.
Maybe a thick 'belt' .
All it is is a large block of metal to make sure you are measuring what you want to measure, not something else.

Can you not follow the circuitry I linked to in Wikipedia for the RTD or thermistor ?
It is very easy, but may not be your subject, which is why I asked.
I did something very similar in my first year Chemistry, back in the 1960s with a tiny silicon diode temperature sensor.
But the temperature was lower.

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4 minutes ago, studiot said:

 

The purpose of the large block is to make sure it is at a common temperature with Leidenfrost ring.
That also allows it to offer support for the thermometer.
You may need to scratch your head a bit to work out a suitable shape to fit to the ring.
Maybe a thick 'belt' .
All it is is a large block of metal to make sure you are measuring what you want to measure, not something else.

Can you not follow the circuitry I linked to in Wikipedia for the RTD or thermistor ?
It is very easy, but may not be your subject, which is why I asked.
I did something very similar in my first year Chemistry, back in the 1960s with a tiny silicon diode temperature sensor.
But the temperature was lower.

I will be eating right now. I will be back with an answer in about an hour or so.

42 minutes ago, studiot said:

 

The purpose of the large block is to make sure it is at a common temperature with Leidenfrost ring.
That also allows it to offer support for the thermometer.
You may need to scratch your head a bit to work out a suitable shape to fit to the ring.
Maybe a thick 'belt' .
All it is is a large block of metal to make sure you are measuring what you want to measure, not something else.

Can you not follow the circuitry I linked to in Wikipedia for the RTD or thermistor ?
It is very easy, but may not be your subject, which is why I asked.
I did something very similar in my first year Chemistry, back in the 1960s with a tiny silicon diode temperature sensor.
But the temperature was lower.

Okay I took a look at the wikipedia page. I read about the different types of RTD's from which i concluded that a thin film RTD would probably work best. Like you said in the comment below "Can you not cement a small RTD (resistance temperature detector) to the ring and set up a suitable measuring bridge ?". You probably mean that I should remove the epoxy glass that is present on most thin film RTD's and solder the whole maze of wire tot the ring. Is the image below what you mean?

On 11/3/2019 at 3:26 PM, studiot said:

Can you not cement a small RTD (resistance temperature detector) to the ring and set up a suitable measuring bridge ?

https://en.wikipedia.org/wiki/Resistance_thermometer

You have given no idea how big the ring is so I can't be more detailed.

RTD.png.9d0818a1339bbf184ae406a0ddf837e6.png

image.png.29409d08b9b5f99049fea8aa51b6d6e0.png

You are also talking about a 'Measuring bridge' but can't you just measure the resistance using a multi meter?

 

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1 hour ago, RaytjeKn said:

You are also talking about a 'Measuring bridge' but can't you just measure the resistance using a multi meter?

You have an accurate enough multimeter on a budget?

I was referring to one of these.

Quote

Wikepedia

iring configurations

Two-wire configuration

Two-wire resistance thermometer

The simplest resistance-thermometer configuration uses two wires. It is only used when high accuracy is not required, as the resistance of the connecting wires is added to that of the sensor, leading to errors of measurement. This configuration allows use of 100 meters of cable. This applies equally to balanced bridge and fixed bridge system.

For a balanced bridge usual setting is with R2 = R1, and R3 around the middle of the range of the RTD. So for example, if we are going to measure between 0 and 100 °C (32 and 212 °F), RTD resistance will range from 100 Ω to 138.5 Ω. We would choose R1 = 120 Ω. In that way we get a small measured voltage in the bridge.

Three-wire configuration

Three wire RTD Wheatstone bridge

In order to minimize the effects of the lead resistances, a three-wire configuration can be used. The suggested setting for the configuration shown, is with R1 = R2, and R3 around the middle of the range of the RTD. Looking at the Wheatstone bridge circuit shown, the voltage drop on the lower left hand side is V_rtd + V_lead, and on the lower right hand size is V_R3 + V_lead, therefore the bridge voltage (V_b) is the difference, V_rtd - V_R3. The voltage drop due to the lead resistance has been cancelled out. This always applies if R1=R2, and R1, R2 >> RTD, R3. R1 and R2 can serve the use of limiting the current through the RTD, for example for a PT100, limiting to 1mA, and 5V, would suggest a limiting resistance of approximately R1 = R2 = 5/0.001 = 5,000 Ohms.

Four-wire configuration

Four-wire resistance thermometer

The four-wire resistance configuration increases the accuracy of measurement of resistance. Four-terminal sensing eliminates voltage drop in the measuring leads as a contribution to error. To increase accuracy further, any residual thermoelectric voltages generated by different wire types or screwed connections are eliminated by reversal of the direction of the 1 mA current and the leads to the DVM (digital voltmeter). The thermoelectric voltages will be produced in one direction only. By averaging the reversed measurements, the thermoelectric error voltages are cancelled out.[citation needed]

 

Your main difficulty is that you need to read above the max junction temperature of most semiconductors, which is in the region of 125 - 150 degrees C.
Otherwise it would be easy, the whole lot could be bought in a cheap chip upgrading my silicon diode.
A silicon dioded might survive to 210 but it would be such it and see. The forward voltage on the junction falls at 2millivolts per degress C.

See also the discussion here

https://picaxeforum.co.uk/threads/temperature-sensor-up-to-250-degrees-c.26172/

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9 minutes ago, studiot said:

You have an accurate enough multimeter on a budget?

I was referring to one of these.

 

Your main difficulty is that you need to read above the max junction temperature of most semiconductors, which is in the region of 125 - 150 degrees C.
Otherwise it would be easy, the whole lot could be bought in a cheap chip upgrading my silicon diode.
A silicon dioded might survive to 210 but it would be such it and see. The forward voltage on the junction falls at 2millivolts per degress C.

See also the discussion here

https://picaxeforum.co.uk/threads/temperature-sensor-up-to-250-degrees-c.26172/

I have a multimeter which I seems like it could measure the resistance. The RTD i mentioned earlier from TE, has a data sheet which provides a graph. It shows the connection between the temperature and the resistance. My multimeter should quite easily be able to measure such high resistances. So I think I don't need the circuits you delivered me. I think it should be as easy as connecting the wires of my multimeter to the probes of the RTD without any other circuitry, read the readings of the multimeter (Ohms) and see what the according temperature would be. But would like I asked earlier it just be a matter of soldering the wires (PICTURE BLUE) to the ring and removing the epoxy glass (PICTURE YELLOW).

image.png.8f41ff350c7c653bcedd4561630b340f.png

image.png.561f771a10d3f2fdbdd874940569c4bc.png

MultiMeter.jpg

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2 hours ago, RaytjeKn said:

But would like I asked earlier it just be a matter of soldering the wires (PICTURE BLUE) to the ring and removing the epoxy glass (PICTURE YELLOW).

If you do that the aluminium will short circuit the resistor and you won't get a reading.

There are glues that will stand 210C without any trouble

The biggest problem you face is that an object like that ring, in air, doesn't have " a temperature".

Bit's of it will be warmer than others.

2 hours ago, RaytjeKn said:

I think it should be as easy as connecting the wires of my multimeter to the probes of the RTD without any other circuitry, read the readings of the multimeter (Ohms) and see what the according temperature would be.

It should be.
It's not going to be the most accurate measurement in the world, but you probably don't need that.

You can improve the accuracy significantly by putting some sort of insulation on the temperature probe so that   the air doesn't cool it much. A scrap of glass  wool is probably good enough

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6 hours ago, studiot said:

I have asked for guidance as to how much help to offer, but here are some thoughts.

!

Moderator Note

My opinion (no other mods have commented on your report yet) is that helping out with this sort of experimental project does not need to be constrained as much as Homework Help questions. The difference, to my mind, is that there is not a "right answer" that you can give; almost by definition, all you can do is help the OP towards a solution. I can't see a problem with asking for advice from people with some expertise in the subject.

 
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11 hours ago, John Cuthber said:

If you do that the aluminium will short circuit the resistor and you won't get a reading.

There are glues that will stand 210C without any trouble

The biggest problem you face is that an object like that ring, in air, doesn't have " a temperature".

Bit's of it will be warmer than others.

It should be.
It's not going to be the most accurate measurement in the world, but you probably don't need that.

You can improve the accuracy significantly by putting some sort of insulation on the temperature probe so that   the air doesn't cool it much. A scrap of glass  wool is probably good enough

I guess I would need highly heat conductive glue. So you are suggesting to glue the RTD with a really thin layer of glue tot the ring. Which part of the RTD should I glue to? The plexiglass side or the platinum? Yes it doesn't have to be accurate tot the 3rd decimal, but I would like it to be around ±3°C. What is your intention with the glass wool exactly?

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14 hours ago, Strange said:
!

Moderator Note

My opinion (no other mods have commented on your report yet) is that helping out with this sort of experimental project does not need to be constrained as much as Homework Help questions. The difference, to my mind, is that there is not a "right answer" that you can give; almost by definition, all you can do is help the OP towards a solution. I can't see a problem with asking for advice from people with some expertise in the subject.

 

Thanks. +1

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15 hours ago, Strange said:
!

Moderator Note

My opinion (no other mods have commented on your report yet) is that helping out with this sort of experimental project does not need to be constrained as much as Homework Help questions. The difference, to my mind, is that there is not a "right answer" that you can give; almost by definition, all you can do is help the OP towards a solution. I can't see a problem with asking for advice from people with some expertise in the subject.

 

O it definitely shouldn't this question is a part so small of the whole part. My work is to make a report about a certain subject. Which in my case is Generating electricity with the Leidenfrost effect. We are not oblidged to conduct an experiment, but we are. We are also allowed to get any help we get, this is also research. Me discussing and asking questions in this manner is also a way of research. My teacher totally allows this. I don't exactly know what this report was, but this is my opinion.

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But I want to bring back my initial idea. I thought of using black paint which I put on the sides of the ring. Because of the really high emissivity of a black surface it is ideal to measure the temperature of the paint using a IR thermometer which I already have. Only concern I have using this technique would be, that the paint's temperature might be a lot lower because of the bad heat conductivity of non metals. Although if I put a very thin layer on, I don't think it would really be a problem. Also I found this product: https://www.conrad.nl/p/voltcraft-tp-205-oppervlaktesensor-100-tot-300-c-sensortype-k-1661150. Might also we worth it.

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