YiHi SX Mini M TCR Values List

[ShowerHead]

With the release of the TCR firmware for the SX Mini M, I'd like to find correct values for different wires without scanning through 1000s of posts in various threads.

Here's my initial thoughts on TCR values for common wire.
Definitely feel free to add/correct this!

Ni200- 0.0052
Ti (Grade 1)- 0.0035
SS
304- 0.001050
316- 0.000915
317- 0.000875
410- 0.001550
430- 0.001380

Of course, on the M you will need to round some values. The SS316 becomes 0.00092 or 0.00091 as the digits available for adjustment don't support that much precision.

 

[IgiPit]

Hello.
The best TCR values depend on the temperature limit you set into the box. If you vape with TC in the range 200°C - 300°C the titanium gr1 TCR should be 0.00367 and not 0.0035.

Anyway at steam engine - wire wizard you will find the TCR in the vaping range for most of wire materials.

 

[ShowerHead]

Hello.
The best TCR values depend on the temperature limit you set into the box. If you vape with TC in the range 200°C - 300°C the titanium gr1 TCR should be 0.00367 and not 0.0035.

Anyway at steam engine - wire wizard you will find the TCR in the vaping range for most of wire materials.

I dont think the TCR depends on temp you vape at. It is a property of the metal.

 

[Kraken_Up]

TCRs are different for certain materials at certain temps. The easiest example of this is Ni200. If you Google it's TFR curve or pull it up on steam engine you'll see it is not linear. You should use a TCR in the range of temperatures you intend to limit at.

 

[dr3d]

Hello.
The best TCR values depend on the temperature limit you set into the box. If you vape with TC in the range 200°C - 300°C the titanium gr1 TCR should be 0.00367 and not 0.0035.

Anyway at steam engine - wire wizard you will find the TCR in the vaping range for most of wire materials.

TCRs are different for certain materials at certain temps. The easiest example of this is Ni200. If you Google it's TFR curve or pull it up on steam engine you'll see it is not linear. You should use a TCR in the range of temperatures you intend to limit at.

Actually ... yes, no and maybe so. A TCR does vary according to temperature. However, inputting the actual TCR for the actual target temperature won't help you achieve that target temperature. Inputting a "Manual TCR" is always going to be a compromise. Hitting targets requires the mod to do the "correct" calculation for every degree change that happens between resting temperature and target temperature.

This means that entering the TCR for 420F as a "Manual TCR" entry will not yield a coil temperature of 420F. It will be close to the degree that the wire selected has a TCR which is stable across the range defined from the resting temperature to the target temperature. This means that performance can sometimes be improved by inputting a manual TCR value which is different than the actual wire TCR at the target temperature.

 

[notarobot]

This means that entering the TCR for 420F as a "Manual TCR" entry will not yield a coil temperature of 420F. It will be close to the degree that the wire selected has a TCR which is stable across the range defined from the resting temperature to the target temperature. This means that performance can sometimes be improved by inputting a manual TCR value which is different than the actual wire TCR at the target temperature.

Actually, this isn't true. Let me quote what I wrote in the "TC Beyond" thread:

With a TCR, the "real" temp/resistance curve is approximated by a straight line. It is a good idea to choose the line in such a way that it crosses the curve near the temperature range used for vaping. E.g. the "TCR for 200ºC" corresponds to a line crossing the curve at 20ºC and 200ºC. Near these points, this approximation is good. In between (e.g. at 100ºC), it may be not that good.

By definition, the TCR for a certain target temperature ensures that the linear approximation and the real curve will have common resistance value for that temperature (i.e. they cross each other).

 

[IgiPit]

I dont think the TCR depends on temp you vape at. It is a property of the metal.

No, it isnt. TCR is not a material characteristic, it is the characteristic of the linear approximation of the Resistivity vs Temperature (R-T) material curve. Thus, the TCR depends on both the material and the approximation method used. The simple way is to linear interpolate the R-T curve at two points, say at temperatures T0 and T1 where T0 is the reference temperature (say 20°C) and T1 is a temperature near the TC limit you will use.

If you set the TC to T1 and carefully initialize the "cold" resistance and temperature values at your sx350 mini (with sw update v2.32), than the box temperature measure will be "exact" at TC (not taking into account of other errors).

 

[ShowerHead]

Since the TCR is a value given for a particular wire, and since I do not see a range being given, I will assume that TCR is not variable and does not need set for a particular temp range. Setting the temp on the SX Mini M with the current firmware is to allow the device to know the starting temp of the unit/coil so it can adjust its internal algorithms away from the default 68F value.
This is the info from the Wire Wizard for Ti (Grade 1):

TCR in vaping range 3660 ×10-6
The info box that appears when you hover over this is: The relative change in resistance between 20C (68F) and 300C (572F)
Note the fixed number for TCR for a given wire. The given TCR does not change with temp.

 

[IgiPit]

Since the TCR is a value given for a particular wire, and since I do not see a range being given, I will assume that TCR is not variable and does not need set for a particular temp range. Setting the temp on the SX Mini M with the current firmware is to allow the device to know the starting temp of the unit/coil so it can adjust its internal algorithms away from the default 68F value.
This is the info from the Wire Wizard for Ti (Grade 1):

TCR in vaping range 3660 ×10-6
The info box that appears when you hover over this is: The relative change in resistance between 20C (68F) and 300C (572F)
Note the fixed number for TCR for a given wire. The given TCR does not change with temp.

Fine, you are coming to the point. Steam engine declares the TCR it displays as the coefficient that linearly interpolates the two R-T points corresponding to T0=20°C (68F) and T1=300°C (572F).
If Lars Simonsen (the author) had chosen to interpolate the R-T curve at T1=427°C (800 F), the TCR would be 0.0035, exactly the TCR value reported in your first post and this is not a coincidence.
If you chose titanium 1 in the wire wizard and click at the graph tab in the Temperature control results box, you will see the real R/R0 vs T curve where R0 is the resistance at T0 ( R/R0 is known as the Temperature Factor of Resistance or TFR). Actually also the TFR curve is an approximate representation of the real material behavior (it is a piecewise linear approximation of experimental data at temperature points [-50,20,100,150,200,250,300,427 ] °C) but this is not important here.
What is really important is that you realize that the R-T curve is not a perfectly straight line . Thus if you want to represent that curve with ther linear function

R=R0 * ( 1 + TCR * ( T - T0) ) [#]

you have to decide how to evaluate the TCR coefficient from the experimental data. The simple way is linear interpolation at a given temperature T1, that is by imposing

R1=R0 * ( 1 + TCR * ( T1 - T0) ),

that is

TCR= ( R1/R0 -1)/ ( T1 - T0) = ( TFR1 -1)/ ( T1 - T0)

Choosing T1=200°C (392F) , being TFR(200)=1.66318 (experimental data) you get TCR=0.00368
Choosing T1=300°C (572F), being TFR(300)=2.02477 (experimental data) you get TCR=0.00366
Choosing T1=427°C (800F), being TFR(427)=2.45116 (experimental data) you get TCR=0.00357

Lars decided to evaluate the TCR at T1=300°C (572F) because doing so the linear approximation [#] is exact at 300°C and very accurate in the whole 200-300°C range used in TC.

I hope I have clarified the issue.
Regards

 

[ShowerHead]

Fine, you are coming to the point. Steam engine declares the TCR it displays as the coefficient that linearly interpolates the two R-T points corresponding to T0=20°C (68F) and T1=300°C (572F).
If Lars Simonsen (the author) had chosen to interpolate the R-T curve at T1=427°C (800 F), the TCR would be 0.0035, exactly the TCR value reported in your first post and this is not a coincidence.
If you chose titanium 1 in the wire wizard and click at the graph tab in the Temperature control results box, you will see the real R/R0 vs T curve where R0 is the resistance at T0 ( R/R0 is known as the Temperature Factor of Resistance or TFR). Actually also the TFR curve is an approximate representation of the real material behavior (it is a piecewise linear approximation of experimental data at temperature points [-50,20,100,150,200,250,300,427 ] °C) but this is not important here.
What is really important is that you realize that the R-T curve is not a perfectly straight line . Thus if you want to represent that curve with ther linear function

R=R0 * ( 1 + TCR * ( T - T0) ) [#]

you have to decide how to evaluate the TCR coefficient from the experimental data. The simple way is linear interpolation at a given temperature T1, that is by imposing

R1=R0 * ( 1 + TCR * ( T1 - T0) ),

that is

TCR= ( R1/R0 -1)/ ( T1 - T0) = ( TFR1 -1)/ ( T1 - T0)

Choosing T1=200°C (392F) , being TFR(200)=1.66318 (experimental data) you get TCR=0.00368
Choosing T1=300°C (572F), being TFR(300)=2.02477 (experimental data) you get TCR=0.00366
Choosing T1=427°C (800F), being TFR(427)=2.45116 (experimental data) you get TCR=0.00357

Lars decided to evaluate the TCR at T1=300°C (572F) because doing so the linear approximation [#] is exact at 300°C and very accurate in the whole 200-300°C range used in TC.

I hope I have clarified the issue.
Regards

No, actually you are not clarifying anything.
Except when you post that the figure I gave above is the figure given for TCR for that particular wire.
If you'd like to spend the time to decide what temp you are vaping at (an inexact value to be sure), then find a number that coincides with it, cool.
I like a single number that provides me a great vape with a given wire. And, that single number is the one that is listed above, as well as the single number given by the site you reference.
Which is also what I'm asking for here. You have run far from the original post topic.

 

[IgiPit]

No, actually you are not clarifying anything.
Except when you post that the figure I gave above is the figure given for TCR for that particular wire.
If you'd like to spend the time to decide what temp you are vaping at (an inexact value to be sure), then find a number that coincides with it, cool.
I like a single number that provides me a great vape with a given wire. And, that single number is the one that is listed above, as well as the single number given by the site you reference.
Which is also what I'm asking for here. You have run far from the original post topic.

Sorry that I have not explained well and run far from the topic.
But at least now you accepted the 0.00366 TCR Titanium gr1 value instead of the original post value of 0.0035. Anyway it would not implied a great error (4.3 %) corresponding to only 12 °C in temperature difference if you set the TC at 300°C.
bye