Atomizer analyzer: (Kanthal) vs (Temp) reading for "Nominal Ohms"?

[ndb]

Well, I give up.
I can't figure out what the two different values for Nominal Ohms actually mean.

I kind of assume the "Nominal Ohms" "(Kanthal)"-qualified reading is whatever the "Raw Ohms" value is, minus the configured mod resistance, but the other value, the one qualified with "(Temp)" I can't wrap my head around.

I'm currently looking at my K4 with a titanium coil, with cold reading of 0.25 on a VS200 (mod resistance came in configured at 0.07):

Raw Value: 0.275
Nominal Ohms: 0.268 (Kanthal), 0.261 (Temp) 
Cold Ohms: 0.251
Room Temp: 84.32

So, 0.275 minus mod-resistance(=0.007) = 0.268 and that's ok, but what does the 0.261(Temp) represent?

I suspect it has something to do with the "Cold Ohms" reading and the current Room Temperature, but I can't figure it out.

Also, Room Temp it's a bit high, since my room's thermometer says 26C (78.8F), and the mod was not used since yesterday.
My HanaV200, which for everything else I consider a worse and less refined device, does actually reports 79.2F
Shouldn't Vaporshark have already set all case parameters correctly for the temperature to be OK?

Thanks for any info you can provide.

Andrea.

[James]

The Kanthal Nominal Ohms is the resistance for a coil that is not temperature-sensing. So, the raw Ohms minus the mod resistance.

The Temp Nominal Ohms is the resistance the coil, if temperature-sensing, would read at 70 Fahrenheit. We normalize it to this standard temperature (this is what it would show on-screen as well) because otherwise one cannot really compare coils.

[ndb]

Thanks James, that is somehow along the lines of what I was thinking, but couldn't be sure of.

The problem is that now this has opened another basket of doubts that I hope you'll be able to help me with:

1. this is what it would show on-screen as well 

   Do you mean the "Cold Ohms"? Isn't that 0.251 in my example? In other words, what's the relation between the "normalized-to-standard-temperature" (i.e. 0.261 in my example) and "Cold Ohms" then?
2. How can my cold ohm reading be 0.251 if the normalized temp is 0.261? Wouldn't that mean that my cold ohm was "acquired" at a temp. well below 70F then? The % variation between 0.251 and 0.261 is 0.01/0.251 ~= 4%, which considering a TiGr1 TCR of 0.0035 would mean dT = 0,04/0,0035 ~= 11 C  = 19,8F, and that would mean my cold ohm value was acquired at 70F - 19.8F = 50.2F, which I'm quite sure was not the case.
3. More generally, I'm not sure anymore of how the cold ohm has to be interpreted: is it just the actual acquired value of the resistance, or is it also somehow "normalized" to a certain reference temp? IOW, if I connect an atty while both the mod are at 90F, will the cold ohm value be what the actual resistance was when they got connected, or it will be the resistance that the coil would have had at 70F?

[VapingBad]

They use the temp sensor on the board and track changes in temp against changes in coil res while it in idle and cooling to refine the cold res and probably use the board temp with the data from the thermal on the case as the temperature of a new coil and not just assume 70 F.

[ndb]

They use the temp sensor on the board and track changes in temp against changes in coil res while it in idle and cooling to refine the cold res and probably use the board temp with the data from the thermal on the case as the temperature of a new coil and not just assume 70 F.

Thanks @VapingBad, I understand that and it makes sense.
I think it would then be reasonable to assume the "cold-ohm" value displayed on the mod screen is always something normalized to some reference temperature, otherwise "refining it" would not make much sense to me, as you can't define an "absolute" true value for a temperature sensing coil without saying at what temperature you're referring it.
Am I right?
IOW: the on-the-mod-displayed ohm value (the cold ohm, right?) is the estimated value of the attached resistance at a reference temperature, and it is continually adjusted/refined by the chip by "cross-checking" the res-value when idle with the actual temperature measured by the on-board sensor.

I think that if that's right, even putting the mod+atty in a freezer, shouldn't change too much the on-the-mod-displayed value, as it should correct the actual value and keep normalizing it to its reference temperature whatever that is.
I would do this myself just out of curiosity, but I'm currently traveling with no easy access to fridges and that sort of things, so If anybody could confirm my understanding is correct I'd be very happy. 

Then the only thing that's still a bit fuzzy is why in my case I was getting a difference btw the 0.261 (Nominal-Temp) value and the 0.251 (Cold Ohm)... 

Sorry for being a pain, I just really like to fully understand how things work as this really helps me in getting the most out of this excellent board.

[VapingBad]

Yes cold ohms on the screen and as James said that includes the mod's internal resistance if set (also part of what refinement does is to work out a resiatance offset for the mod & atty).   IIRC on hte DNA40 the refinement kicks in about 5 mins into idle and continues for up to 55 mins, but Evolv have been working on refinement a lot so it has probably changed so I could not be definite about any of the details.    Not sure about freezing it that may be going too far I don't know, maybe put it in front of the air con in a car would be better.

Is the difference btw the 0.261 (Nominal-Temp) value and the 0.251 (Cold Ohm) because you have mod resistance set to 0.01 ohm?  or maybe refinement has worked that out, but from James post it should be the mod resistance.

[ndb]

Is the difference btw the 0.261 (Nominal-Temp) value and the 0.251 (Cold Ohm) because you have mod resistance set to 0.01 ohm?

Nope, mod resistance for VS200 came factory set to 0.007, and that accounts for the 0.275 to 0.268 difference btw Raw Ohm and Nominal (Kanthal).

Honestly that 0.261 to 0.251 difference escapes me.

More generally, if the Nominal(Temp) thing is the value of Nominal(Kanthal) value, but normalized to reference temp, I can't understand what's the difference with the cold ohm value.

But there must be some difference, as I always get different values between Nominal(Temp) and Cold Ohm with every atty I tried.

Could it be that Nominal(temp) is the value it would acquire as the Cold Ohm value if you were connecting the atty in that condition for the first time? I.e. 0.261 would become my cold ohm if I could force the chip to re-acquire the Cold Ohm base resistance somehow? And it is just not asking for a new coil because the difference is under the configured 25% threshold?

Wait a minute, I just remembered the atomizer analyzer has something like a "lock ohm" button. Maybe pressing that will force re-acquisition of the Cold Ohm value with the current Nominal(temp) value as per my "if I could force the chip to re-acquire the Cold Ohm base resistance" above?

Unfortunately I'm away with no access to my escribe installation, could anybody try and see if "lock ohm" from the atomizer analyzer makes the Cold Ohm value become what's currently displayed as Nominal(temp)?

[lewisss]

ndb said:

Is the difference btw the 0.261 (Nominal-Temp) value and the 0.251 (Cold Ohm) because you have mod resistance set to 0.01 ohm?

Nope, mod resistance for VS200 came factory set to 0.007, and that accounts for the 0.275 to 0.268 difference btw Raw Ohm and Nominal (Kanthal).

Honestly that 0.261 to 0.251 difference escapes me.

More generally, if the Nominal(Temp) thing is the value of Nominal(Kanthal) value, but normalized to reference temp, I can't understand what's the difference with the cold ohm value.

But there must be some difference, as I always get different values between Nominal(Temp) and Cold Ohm with every atty I tried.

Could it be that Nominal(temp) is the value it would acquire as the Cold Ohm value if you were connecting the atty in that condition for the first time? I.e. 0.261 would become my cold ohm if I could force the chip to re-acquire the Cold Ohm base resistance somehow? And it is just not asking for a new coil because the difference is under the configured 25% threshold?

Wait a minute, I just remembered the atomizer analyzer has something like a "lock ohm" button. Maybe pressing that will force re-acquisition of the Cold Ohm value with the current Nominal(temp) value as per my "if I could force the chip to re-acquire the Cold Ohm base resistance" above?

Unfortunately I'm away with no access to my escribe installation, could anybody try and see if "lock ohm" from the atomizer analyzer makes the Cold Ohm value become what's currently displayed as Nominal(temp)?

Sorry no it doesn't

[xxsteven69xx]

I have found that the cold ohm's is the normalized Ohm's at 70F. 

Raw Value = Live or current resistance with no compensation.

Normal Kanthal = Raw Value minus Mod's resistance.

Normal Temp = Raw Value minus Mod's resistance with some algorithm to give the coils best live estimate of coil. The constant measuring of Ohm's Heats the coil lightly. Kanthal would have no real measurable change with such small heating, but temp control coils it is measurable. The difference here is to compensate for that minute heating.

Cold Ohm's = Estimated resistance at 70F

In short, the normal ohms is the best attempt to give you a correct live reading of coil resistance without the mods resistance factoring in. 

Mods I'm 98% sure this is correct but would love conformation.

[VapingBad]

Well explained xxsteven69xx , I would add than IMO the real time power regulation is still important in non-temp operation for shots ETC. and to keep the power accurate with wires like stainless steel.