Pico problem - How accurate are mods' resistance measurements?

[Hawise]

My Pico doesn't seem to be reading my coil's resistance properly. It's reading a coil 0.1 ohm below my VTwo Mini (which agrees with my NX75 and, more importantly, my ohmmeter and my steam engine calculations, so I have no doubt it's the Pico and not the Mini that's off).

It doesn't seem to have a problem with TC. Despite the discrepancy, I'm getting the same vape at the same temperature settings I was using on the Mini. Nonetheless, I'm a bit wary of using the Pico if it can't read resistance properly. If I were subohming I wouldn't risk it.

Anyone have any ideas about what might be going on?

 

[Eskie]

Unfortunately, these things are not professional grade electronic products, and variability will occur. The fact that TC is OK likely indicates however the resistance is off by is consistent. You might feel the need to have the temp a bit higher or lower than on another mod, but as long as the response is consistent I wouldn't worry about it.

As far as subohming, I don't see why not. Even with a +/- 0.1, a 0.5 ohm build will be just fine. Would I run a 0.1 ohm coil on it? No, but it wasn't built for that type of use in the first place.

 

[Hawise]

Yes, I expect you're right. I've used a handful of mods with TC and I'm used to them being within 0.02 or so, so the scale of the difference surprised me.

 

[Eskie]

Yes, I expect you're right. I've used a handful of mods with TC and I'm used to them being within 0.02 or so, so the scale of the difference surprised me.

I guess it's just the offset. You can make believe it's like using a tare for a scale. The only thing I'd worry about would be if it's not consistent and bouncing around. But if it did that, TC would be all mucked up.

 

[Hawise]

I guess it's just the offset. You can make believe it's like using a tare for a scale. The only thing I'd worry about would be if it's not consistent and bouncing around. But if it did that, TC would be all mucked up.

I wonder if it's an offset or proportional - off 8% or so straight through. I'll have to check it out with a quite different coil sometime.

 

[93gc40]

Could try the ArcticFox firmware... it has adjustment for resistance read errors. And internal mod resistance.

Sent from my SCH-I605 using Tapatalk

 

[DaveP]

Even with the inaccuracies in mod resistance, mods seem to be more in agreement than my clone digital meters. The .92 ohm coil on my Pico reads 1.1 on my Fluke 87 clone and 1.2 on the other Centech meter. I screwed the atomizer on to my RX200S and it reads 1.00 ohms.

IF the vape is tasty, it's all good.

 

[Chodi]

I have several mods and the Pico is always reading under on ohms. That requires a bit high wattage setting on the Pico to achieve the same vape as other mods. Not a very big problem once I realized the difference. I don't find the pico hits as hard as my dual battery mods but that is not a big surprise.

 

[DaveP]

I've seen variance from mod to mod in reading resistance, but it's usually a very small difference. Sometimes, it changes if you screw and unscrew the atomizer to re-seat the connection. You might compare the atomizers to a voltmeter resistance scale, but those aren't exactly lab grade instruments either unless you buy respected brand names and pay high dollar for them.

 

[David Wolf]

Could try the ArcticFox firmware... it has adjustment for resistance read errors. And internal mod resistance.

Sent from my SCH-I605 using Tapatalk

That's awesome, when I install AF I on my Pico I will use that. Even a 0.01 ohm error affects temperature accuracy in TC mode using SS coils.

 

[Hawise]

That's awesome, when I install AF I on my Pico I will use that. Even a 0.01 ohm error affects temperature accuracy in TC mode using SS coils.

Accuracy is important, but consistency is more so. With the Pico I originally posted about, TC works very reliably despite the inaccuracy. I expect that means it's consistently about 0.1 ohm low, so its assessment of the change in resistance as the coil is heated is correct.

If I corrected the resistance, I'd be worried that the TC would go off. In other words, say it reads a cool 1.2 ohm coil as 1.1 ohms. I fire it up, and the resistance rises 0.08 ohms. If it's not corrected, it would read that as 1.18 ohms, conclude that resistance (and therefore temperature) had risen and respond accordingly. If I corrected it, I'd be worried that it would still read the new resistance as 1.18 ohms and calculate that the temperature had not gone up since the coil started out at 1.2 ohms.

Of course, I might be totally wrong about how ArticFox handles corrections.

 

[93gc40]

That's awesome, when I install AF I on my Pico I will use that. Even a 0.01 ohm error affects temperature accuracy in TC mode using SS coils.

But the accuracy.. really only matters when reading the gauges. Or diagnosing problems......

A good vape is a good vape and bad bad....... regardless what the screen says. IMO consistency right or wrong much more important than accuracy. I can adapt.

I do like the ability to correct for errors because it does help with building or issues diagnosis.... just not actual vaping.

I do most of my setup in stealth mode. ... specifically so my opinions are not affected by what t he screen says..... I also like judge flavor and vapor of builds with eyes closed. .. so cloud is not a factor.

Been driving lifted Jeeps and riding Motorcycles all my life......... I'm used to ignoring gauges.

Sent from my SCH-I605 using Tapatalk

 

[David Wolf]

Accuracy is important, but consistency is more so. With the Pico I originally posted about, TC works very reliably despite the inaccuracy. I expect that means it's consistently about 0.1 ohm low, so its assessment of the change in resistance as the coil is heated is correct.

If I corrected the resistance, I'd be worried that the TC would go off. In other words, say it reads a cool 1.2 ohm coil as 1.1 ohms. I fire it up, and the resistance rises 0.08 ohms. If it's not corrected, it would read that as 1.18 ohms, conclude that resistance (and therefore temperature) had risen and respond accordingly. If I corrected it, I'd be worried that it would still read the new resistance as 1.18 ohms and calculate that the temperature had not gone up since the coil started out at 1.2 ohms.

Of course, I might be totally wrong about how ArticFox handles corrections.

But the accuracy.. really only matters when reading the gauges. Or diagnosing problems......

A good vape is a good vape and bad bad....... regardless what the screen says. IMO consistency right or wrong much more important than accuracy. I can adapt.

I do like the ability to correct for errors because it does help with building or issues diagnosis.... just not actual vaping.

I do most of my setup in stealth mode. ... specifically so my opinions are not affected by what t he screen says..... I also like judge flavor and vapor of builds with eyes closed. .. so cloud is not a factor.

Been driving lifted Jeeps and riding Motorcycles all my life......... I'm used to ignoring gauges.

Sent from my SCH-I605 using Tapatalk

I appreciate what you guys are saying, if it''s a good ride, it's a good ride...or vape.
Being an engineer though, I have to look under the hood because well, this is me. I researched the Pico up one side and down the other before and after I got my Pico and started using Temp Control with 316L SS. And what I found is both good and ugly, there are two notable problems with the Pico on Temp Control:

1. Doesn't always lock properly on a new coil if the resistance changes only .02 to .03 ohms with the new coil - still keeps the setting of the previous coil (doesn't matter if you unlock and relock). Even a 0.02 ohm resistance change from coil to coil makes a big difference in temperature accuracy with SS in temperature control if your Pico doesn't give you the "New coil up same down" message and allow you to select new coil so its resistance can be properly set.
I posted the workaround for this here:
Eleaf iStick "pico"

2. Temperature error 50 deg F or more higher than displayed temperature with SS setting for temp control using SS316/316L. I posted the proof and the fix for this here and here:
Eleaf iStick "pico"
Eleaf iStick "pico"
The Pico temperature accuracy isn't bad for nickle and titanium, but if you trust your temperature display using SS on the standard Pico SS setting you're fooling yourself and likely 50 deg F or higher than your display shows. That might matter to folks concerned about aldehydes:
New studies find carcinogens in vg and pg at high temps, even in tootle puffers

As far as stable temperature control goes, the Pico does control well, in fact better than the AL85 per DJLsb Vapes. It just controls it very inaccurately with the standard settings for SS.

My Pico with stock settings controlled my 316L SS build very inconsistently from coil to coil until I researched, did my own testing, and learned tips 1 & 2 above. Now I have it fined tuned with those methods and its running like a well oiled machine with decent accuracy and repeats coil to coil. Folks using the Pico firmware need to rebuild their Pico engines using steps 1 & 2 above

 

[Hawise]

@David Wolf - Have you tested TC accuracy of the eVic Mini? I know they're similar so now I'm wondering if they have the same flaw. I certainly have the new coil issue with my Mini. It's a pain in the posterior to get it to recognize a similar-but-new coil. My own workaround is to switch to VW mode, remove the tank and press fire, screw the tank back in and get it to recognize the resistance while in VW mode, and switch back to TC mode. My experience is that it only works if you switch to VW and get the "no atty" message there - I can't just do it while staying in TC. (And when that fails, I dance three times clockwise around the mod while wearing purple and chanting in Sanskrit.)

 

[David Wolf]

@David Wolf - Have you tested TC accuracy of the eVic Mini? I know they're similar so now I'm wondering if they have the same flaw. I certainly have the new coil issue with my Mini. It's a pain in the posterior to get it to recognize a similar-but-new coil. My own workaround is to switch to VW mode, remove the tank and press fire, screw the tank back in and get it to recognize the resistance while in VW mode, and switch back to TC mode. My experience is that it only works if you switch to VW and get the "no atty" message there - I can't just do it while staying in TC. (And when that fails, I dance three times clockwise around the mod while wearing purple and chanting in Sanskrit.)

Haha you sound like me, I tried for an hour to get the "New coil up same down" message to come in consistently, no atomizer, put on atomizer, turn on, turn off, etc. and even with all I read I finally had to experiment to get the workaround I posted above that has worked every time. And looks like you have it figured out for the eVic Mini there!
I don't have an eVic Mini, however DJLsb Vapes does some great testing, and has this video for the eVic VTC Mini with version 3.0 firmware, not sure if this is the device/firmware you have. It appears to have outstanding accuracy on temp control for SS:

 

[DaveP]

My Pico Dual came with SS316L TCR set at 120 and it popped and crackled when I'd hit the fire button. A setting of 92 calmed it down. The range for SS316 is pretty wide.

 

[David Wolf]

My Pico Dual came with SS316L TCR set at 120 and it popped and crackled when I'd hit the fire button. A setting of 92 calmed it down. The range for SS316 is pretty wide.

You might consider a setting of 80 and you should be far more accurate on your temperature display (see my post a couple posts above with links to testing Pico problem - How accurate are mods' resistance measurements?). However you likely will have to increase your temperature setting to be happy. Also note issue 1 with the Pico often not detecting a new coil and the workaround I found for that.
I'm currently vaping 316L 28 AWG, 0.62 ohm 6 wrap 2.5mm spaced CLR coil in an Amor tank, M1 set to 80, setting of 380-390 deg F, 11W limit, tootle puffing in TC

 

[TrollDragon]

Kudos to you @David Wolf for experimenting and getting TC running to your liking on a $25 mod.

There is a lot of inconsistency in SS316L wire between manufacturers, so tweaking the TCR value of your SS wire is recommended. You might want to pick up a spool of TEMCo's SS316L, it will be quite different then UD's SS316L or other China wire.
TEMCo Stainless Steel Wire 316L Non-Resistance AWG TEMCo Industrial

Since you are using 28g, you might want to try some SS430 from Unkamen. The SS430 has zero nickel content and uses a TCR of 138. I use it a single wire or twisted with 2 or sometimes 3 strands when I want a bigger gauge coil. It's only $10 for a 200' spool and they ship quickly.
https://www.creatingunkamen.com/col...e-nickel-free-introductory-sale-100-guarantee

An alternative that I use more often these days is NiFe70 from Kidney Puncher, it has a TCR of 525 and is the closest to Ni200 in resistance swing. The higher the resistance change, the easier it is for a mod to measure and control the output. Also NiFe70 can be used safely in regular VW mode unlike Ni200 or Ti, but unfortunately KP doesn't carry any 28g.
http://www.kidneypuncher.com/nifethal-70-wire-30ft-spool/

 

[DaveP]

You might consider a setting of 80 and you should be far more accurate on your temperature display (see my post a couple posts above with links to testing Pico problem - How accurate are mods' resistance measurements?). However you likely will have to increase your temperature setting to be happy. Also note issue 1 with the Pico often not detecting a new coil and the workaround I found for that.
I'm currently vaping 316L 28 AWG, 0.62 ohm 6 wrap 2.5mm spaced CLR coil in an Amor tank, M1 set to 80, setting of 380-390 deg F, 11W limit, tootle puffing in TC

One of the major issues in contact resistance in my job stemmed from dissimilar metals in low voltage (5v) connectors. It's one of the reasons we all carried a bottle of De-Oxit in our toolbags. When you add up the voltage drop in a wiring harness from a card cage all the way out to the components it controlled, ten feet away from the controlling circuit board connector resistance was significant.

In our mods, that's also true. You have gold plated mod connectors mating with steel atomizer contact screws that have a screwdriver slot in the center. Sometimes, you can loosen and tighten the atomizer and get several readings. Minimizing that resistance does a long way toward calming down the electronics.

As you mentioned, it's hard to get the mod to recalculate the actual resistance of the atomizer by unscrewing it and hitting fire again unless there's a lot of change.

 

[David Wolf]

Kudos to you @David Wolf for experimenting and getting TC running to your liking on a $25 mod.

There is a lot of inconsistency in SS316L wire between manufacturers, so tweaking the TCR value of your SS wire is recommended. You might want to pick up a spool of TEMCo's SS316L, it will be quite different then UD's SS316L or other China wire.
TEMCo Stainless Steel Wire 316L Non-Resistance AWG TEMCo Industrial

Since you are using 28g, you might want to try some SS430 from Unkamen. The SS430 has zero nickel content and uses a TCR of 138. I use it a single wire or twisted with 2 or sometimes 3 strands when I want a bigger gauge coil. It's only $10 for a 200' spool and they ship quickly.
28 gauge Stainless Steel Wire - 430 Grade Nickel Free - 200 feet - 100% Guarantee - Creating Unkamen

An alternative that I use more often these days is NiFe70 from Kidney Puncher, it has a TCR of 525 and is the closest to Ni200 in resistance swing. The higher the resistance change, the easier it is for a mod to measure and control the output. Also NiFe70 can be used safely in regular VW mode unlike Ni200 or Ti, but unfortunately KP doesn't carry any 28g.
Nifethal 70 Wire 30ft Spool

Hey TD I really appreciate the links!
I'm vaping Temco SS316L right now, its annealed so easy to work, vapes with no metallic taste at all. I really trust wire from a US manufacturer, and theirs is always clean, be it SS, Kanthal, or Nichrome 80. Plus free shipping, and if you order it from amazon you typically get a discount for ordering two of any rolls of wire.
I"ve also bought wire from Kidney Puncher, and found it to be good wire.

You have me interested in the 28 AWG SS430 from creatingunkamen. Do you know if its annealed and easy to work, or is it really springy?I do wish I knew their source. Thats certainly a good price for 200 ft, and no doubt it would improve temperature control. I see a lot of sources in the UK, but the only US SS430 I find is large rolls from US manufacturers, no small rolls for vapers. I could buy a 1000 ft made here in the US though, lol. I've read up on the corrosion resistance of SS430, looks like fine vaping wire to me. I will definitely give it a shot at some point.
Oh man, my goal on my very sold but very cheap priced Picos is to eventually put Artic Fox firmware on one of them (I have another Pico just hit the continent and will be here soon), tune it with PI congtrol,calibrate resistance offset, and have it vaping SS in temperature control so good it'll give a DNA75 a run for its money. A Pico on steroids, vrooom
While I might not quite get there, the Pico does have decently stable control (but not accuracy on SS without tweaks as you've read), and even now is giving me good temp control on SS316 though initially it didn't look promising without tweaks, so the measuring input and control output electronics have the capability of utilizing some high performance tuning with advanced firmware.