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T12 clone vs 888, practical test results

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thm_w:
T15-D52 would be the closest chisel tip at 5.2mm. You could look at some of the large knife tips as well.
Or the super wide style: https://www.aliexpress.com/item/4000179733134.html

I measured the metcal plating thickness of 0.3mm here: https://www.eevblog.com/forum/reviews/metcal-sttc-soldering-cartridgetip-teardown/msg3553345/#msg3553345
But that was total thickness, and the iron thickness would be thinner at the tip.
The thing is unless I destroy a new tip its going to be hard to determine plating thickness. I'll see if I can do a T12 at some point.

I'm not sure I totally buy the theory as an almost dead tip would then perform significantly better than a new tip.

KL27x:

--- Quote from: leStoppe on July 22, 2021, 11:40:18 am ---
--- Quote from: KL27x on July 15, 2021, 04:34:51 am ---The T12 tip with the sensor-coupling error is expected to do worse. And it does.

--- End quote ---
I didn't understand this, shouldn't the T12 have better coupling and therefore reduced error?


--- Quote from: KL27x on July 15, 2021, 04:34:51 am ---That's the problem with the cheap T12 clones. At least the two I have do no error correction. Without any attempt to do that, there's no way a T12 iron can match the temperature control of an old 888 iron.

--- End quote ---

Are you referring to the calibration in the station. I'm not following the hype but I'm curious because I've designed and built an 888D style station, gathering a lot of char data in the process. I don't have any data on the T12s though.

--- End quote ---

In the T12 iron, the heater is the sensor. So the sensor is unable to sense the temperature of the tip with any accuracy. Not directly. It senses the temperature of the heater.

You can make an analogy with a toaster. You have some red hot coils heating the toast. Then the toast is the thing that must be hot enough to melt the butter. So in the 888 type iron, the temp sensor is on the toast. When the toast reaches butter-melting temp, it shuts off the heater. When that big slab of toast starts to cool a degree, then the heater turns back on. Keeping the toast the right temp.

In the T12 iron, the temp sensor is placed on the nichrome wires. So the nichrome wires will reach butter melting temp in 2 seconds. But the toast isn't hot yet.

This has nothing to do with calibration.

For a T12 iron to have accurate temperature control, it needs error correction for the sensor-heater coupling. And the cheaper clones don't do this. So they sag when under load. The more cold butter you pour on the toast, the more the toast drops in temp. But the heater wires are still red hot and are not as affected. The more load, the more sag. But on the plus side, the cartridge tip design allows for high power output without warming up the handle very much.

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