Apologies for the delay in replying. Quite apart from the need to chew over what you were saying, "Real Life" concerns had also intruded into my thoughts. I'm not talking about the more mundane RL concerns of the great unwashed you understand, more those of the, nevertheless still mundane, concerns of dealing with the results of shopping (on line - is there any other form of shopping for those of us now stuck between a rock and a hard place when it comes to buying electronic components and such like items?). I won't go into details here but, if you're interested, I've added them as a footnote[1] for you to peruse at your leisure. I've little doubt that I'm merely adding to the shared experience of the collective so make of it what you will.
My thoughts about using a Z80 cpu and 8 bit ADC data were more a vague 'thought experiment" to give the use of the much better endowed and orders of magnitude faster STM32 micro controller actually used in these KSGER soldering stations some context.
I do see the point you're making about using higher resolution data from the tip sensor ADC in being able to more swiftly detect changes around the inflection points of the temperature curves in order to more precisely spot the trends and initiate the correct response in a more timely fashion to minimise the effect of lag.
I suspect being able to differentiate between temperatures separated by only 0.02 deg C is likely to be thwarted by noise in the signal which will need to be filtered out (in the digital domain rather than at the analogue input stage).
Luckily, most of this noise will be relatively high frequency and a low bandwidth of, say, 500Hz or less would likely serve our needs quite nicely in this application. Plenty of time for an STM32 to do the necessary DSP sufficient to perhaps resolve to within half a degree's worth of accuracy which I feel may well be 'overkill' even in this case.
However, like you, I don't have access to any hard data to back up such an opinion. You could well be right in assuming Pace have a valid justification for the use of a 17 bit ADC in their very expensive soldering station kit.
Inspired by that other EEVBlog thread (the OP actually), I soldered an earth strap between the TPHs used by the encoder's mounting tabs to an actual ground connection nearby to address possible ESD issues and added a BY198 diode (in place of the RS1M diode suggested by Floobydust) across the heater connections to ground clamp the flyback pulse produced when the power is cut off to the 4μH's worth of inductance in the 8 ohm heating element and cabling in order to protect both the switching MOSFET and thermocouple amplifier.
Obviously, I was anxious to test out these modifications so plugged it into a repurposed block filter plug adapter which allows connection of an analogue wattmeter so I could immediately see any possible power up overloading effect I may have caused as a result of these modifications.
The point of mentioning all of this is that I could see that the soldering station was applying bursts of power after drawing a steady 80 watts off the mains supply during the initial 4 or 5 seconds heating time to 300 deg phase at the rate of about five to six times per second.
At this 300 deg setting, the critically damped Metrawatt meter movement integrates this pulsating power draw to a reading of 10 watts with a small +/- 2W wobble imposed by the pulsations. Meanwhile, the KSGER indicates a percentage of applied power figure of 7 or 8 percent which seems reasonable enough considering the different points of measurement involved.
Thankfully, I had managed to avoid doing more harm than good (hopefully nothing but good) in making these modifications. It would seem that your 'guesstimate' of a "leisurely 10 reads per second" is pretty well right in the ballpark (if a little less "leisurely" than the update rate seemingly used by the KSGER STM32 control algorithm).
In view of the 0.5μs time constant (worst case whilst the extra clamp diode I've added to complement the body diode in the switching mosfet is handling the flyback pulse current), it strikes me that a 10μs delay from heater current switch off should leave the subsequent sampling of the TC voltage completely unmolested.
A further 31 samples at a modest 50KS/s could be collected over a total off time of just 0.64ms to feed the DSP noise filter algorithm to refine our TC voltage signal so it looks like we needn't have to shut the power off for longer than 1ms in every 100 (or 200 in the case of the KSGER) when ramping the temperature up or maintaining tip temperature with the heaviest duty tip against a heavy duty heatsink load.
In practice, it would seem that even when soldering a 'difficult joint' with the BC3 tip (the most substantial of my bargain pack of ten clone tips) at a 350 deg set temperature, it seems unlikely that the average power percentage will need to go above the 40% mark.
JOOI, I've actually tested that just now with a British two pence coin which I'd previously 'tinned' a few weeks back. It took several seconds to establish a good thermal contact with some fresh multicore solder before the percentage maxed out around the 40% mark.
By blowing hard onto the penny and solder tip, I did manage to raise that to 48% briefly, noticing that the reading on my wattmeter had reached the thirty watt mark as I raised my head to look at the meter. Also noted was the modest 3 or 4 degree sag on the station's indicated tip temperature during all of my 'huffing and puffing' and the more interesting rebound (overshoot if you prefer) to 360 deg before dropping back to the set temperature upon removing the tip from contact with my "difficult test joint".
All in all, I thought this was an excellent result despite not complicating the test with actual tip temperature readings using my FG-100 tip thermometer. However, though such testing might leave me a little less impressed, the best I could do would be to read the unloaded tip temperature. Ideally, I'd need a remote thermocouple that could be applied to the tip and my 'test joint' to get a more accurate assessment of the actual temperatures being achieved in such use.
Since none of my existing collection of DMMs sport such a K type TC probe port, I'm considering buying a K type TC probe which I can connect to the FG-100's TC terminals to read the TC voltage and hence give me a temperature readout. As far as I'm aware, the clip in TCs used by these meters are just a K type TC in a compact form so I should be able to save the expense of buying yet another DMM just for the sake of a K type TC port. If the readings from a remote K type TC agree closely enough, it might be worth modifying the FG-100 to allow a standard K type TC plug ended temperature sensor to be be plugged into it (after removing the clip in TC, of course) for any such future tests.
The other observation I've taken note of since doing the clamp diode modification to the heater circuit (and possibly even before) is the elimination of the "New Tip Instability" issue. It seems my sporadic use of the BC3 tip over the past week or so has successfully completed the "Burn In" process, rendering it entirely stable even right up to the unboosted 450 deg limit (in theory, this could be boosted another 100 deg but I have no desire to subject my BC3 tip to any such further abuse).
Assuming that all such clone tips will settle down to a more civilised behaviour with this KSGER station after a few heating and cooling cycles of use, I'm tempted to put them three at a time in series with a 36v 400VA transformer to dry them out "en masse" without the possible detriment of using DC bias which could activate a (seemingly) temporary electrochemical reaction during the initial drying out phase. If my hypothesis about residual damp and electrochemical reactions is correct, I'd like to minimise any such electrolysis effects even if they do appear to be only of a transient nature.
A basic 12v 24VA transformer based "Tip Conditioner" could become a 'must have' KSGER soldering station accessory for the more prolific user of clone T12 tips.
Whether such an accessory would be of any use to someone who sticks with the more pricey Hakko 'originals' remains an open question. However, in view of Hakko's use of
rectified (unsmoothed) AC to power the tip heaters in the FX-951 soldering stations and the absence of any mention of a need with brand new Hakko tips to do a similar burning in exercise, I suspect not.
In any case, the benefit of a 12v transformer based new clone T12 tip conditioning 'gadget' is an, as yet, untested idea of mine. Even if it does solve the "New Tip Syndrome", it's hardly a marketable good since anyone in the position of using a KSGER or copy T12 soldering station with clone T12 tips will be looking to minimising their spending and, worst still from a marketeer's point of view, more than capable of repurposing a suitable mains transformer from their, no doubt burgeoning pile, of "salvage' to such a basic function (assuming that such a gadget is even desired in the first place).
If this scheme to condition new clone tips with a 12v transformer proves successful, I may well decide to "sell my soul" to Youtube to sign up as a contributor to publicise my "Wizdumb" to the greater world (small as this section of it is) at large.
[Notes]
[1] I've already mentioned that broken Mustool G600 LCD microscope I'd received from Banggood a couple of days ago. Well, the latest upshot to that is that it looks like they want to offer me a refund of its cost (but not the 66 pence shipping insurance) with no mention of what I'm supposed to actually do with the broken unit.
It looks like they don't want me to return it which I suspect is just the economics of the situation (I had suggested quite strongly in my first and previous reply that I didn't want to accept their offer of a replacement if they were expecting me to pay the cost of the return shipping after advising them that a local repair would not be economically viable - their other suggestion).
This afternoon's message from them posed the offer of the refund as a question sans question mark, so I asked for clarification about whether they wanted me to keep hold of the original for their courier to collect or whether they just wished me to dispose of it as I saw fit, also pointing out the fact that they'd left the shipping insurance cost out of their refund calculation. Just for good measure, I asked them to unambiguously state their position with regard to the return, or not, of the broken microscope and my acceptance of their refund offer.
I'm not too bothered about the 66p shipping insurance charge since, following an Ebay breadcrumb trail search, I managed not only to track down a cheaper version with the grotty plastic suction windscreen stand from a seller shipping from within the UK, I managed to find another who was offering the later version with the sturdy aluminium adjustable base for less than a quid more, making the whole deal (the net refund plus cost of the uk sourced replacement) some 47 pence cheaper than the original Banggood price plus shipping insurance charge.
Now, all that remains is for Banggood to confirm the exact details of their refund offer - if they want the damn thing back at their cost, they can have it back - I don't need it any more for its base as an upgrade to that first cheap Ebay find. Coincidentally, I've just this moment (22:23 BST) received a second email from the ebay seller from whom I'd purchased the best of those two Mustool G600 microscope kits earlier this afternoon to inform me that it's now being posted which bodes well for an earlier delivery than the promised Thursday the 3rd of October date.
Past experience with ebay sellers shipping out of UK warehouses has been quite good in regard of timely deliveries. It's been rare indeed for a delivery to over run its promised date of delivery (typically a week after placement of the order) by more than a day or two with most arriving within just two to four days. This is a far cry from the Banggood experience of late (only my very first Banggood order (for that KSGER and some useful accessories btw) managed to arrive within just 8 days of being ordered).
You might think I'd have had enough by now what with a large order that I'd placed on 11th Sep still stuck at the processing stage with no indication as to why it is now four days past its promised shipping date other than to a query I'd slipped into my first reply to their initial response to my reporting the broken microscope kit.
It appears that the problem is "out of stock" ("What! All eight items? Are you serious?" being effectively my response to that information, along with a request for more details so I can decide how best to deal with it). TBH, I'm surprised they hadn't done what they'd done with another large order where they'd split it up, presumably to get what items were in stock shipped out to prevent the out of stock items needlessly holding up the whole order - a point I'd raised in my response to this news.
It will be interesting to say the least as to how they'll respond to my utter disappointment in their handling of this "out of stock" issue. TBH, I can afford to wait a little longer on this order since nothing is urgently needed, not even the 30V10A 4 digit LED display bench supply headline item that I managed to snag for just £37.82 At that price, some ten quid cheaper than even the cheapest ebay/amazon seller alternatives, I can well afford to bide my time.
As I was saying, you might think I'd have had enough of my dealings with Banggood but as it happens, I only went and placed an order for 3 metres of flexible 5 core silicone cable and a DIY kit KSGER FX9501 T12 Soldering Handle for just £6.71.
Again this was an item I had been searching for during the past week or so on Amazon and Ebay only to discover silly prices for the ones with a 4 core cable and the stupid 8 pin din plug intended for the Hakko soldering stations, typically priced at 11 quid and up for something I'd have to spend yet more money on. Searching directly on Banggood's web site had failed to unearth where this little gem had been hidden (it even includes the GX12-5 connectors (both the panel and the handle connectors - Yay!) and it was not until I tried a duckduckgo search with the inclusion of they key word "DIY" that I finally discovered where BG had hidden it.
No cable supplied though, hence the purchase of 3 metres for just £4.14 for me to split into 1.5 metre lengths for the spare and to upgrade the 1 metre cable currently attached to my existing iron handle. I much prefer a DIY assemble it yourself kit over the ready assembled units simply because it saves the time you'd spend taking such ready made handles apart in order to fettle the typically piss poor quality of assembly seen in these items of 'best Chinese manufacture'. This way, you'll know exactly how good the quality of assembly will be before using it in anger.
In spite of several reviewers' prejudices against its cheap "plasticy" construction, I was surprised at how difficult it had proved to be to locate one at the hoped for 'cheap' price point. I had deliberately chosen this particular KSGER T12 soldering station package for this soldering handle, seeing through the reviewers' prejudices to recognise the charms of its quick tip change, light weight and short tip to grip distance with the latter being the overriding charm of its construction in view of its intended purpose of soldering smd components onto cramped circuit boards where the last thing you need is a hulking great tip retention collect to get in the way of a long distance tip. Quite frankly, I'm rather relieved that I was finally able to track down and order another one so cheaply as a spare.
JBG