Calibrating a soldering station using a Fluke Multimeter - Page 1
Forum section: electronics / projects

author: sparkypom
author_rank: Contributor
timestamp: February 08, 2012, 07:25:52 pm
content: I was thinking that I could use a Fluke 80pk-26 Type-K thermocouple which can be used in surface applications and has a measurement range from -40°C to 816°C together with a Fluke 80TK Thermocouple module (Type K) to calibrate my soldering station.Has anyone got any experience of calibrating iron tips this way or similar? Or is there is a cheaper way to do it ?

author: saturation
author_rank: Super Contributor
timestamp: February 08, 2012, 08:43:21 pm
content: To get a proper reading liquid solder on the soldering iron tip must immerse the thermocouple sensor. If you have a small soldering iron tip, it can get more difficult as the thermocouple could heat sink so much heat preventing solder from liquifying, so typically the thermocouple used in are thin wire types.What I found is very close to using the proper way, a tip thermometer [ you can buy Hakko counterfeit ones on eBay for under $10, real ones cost $200], is just use eutectic solder. Apply it to a clean tip and since it melts at a 'precise' temperature, that's the setting you can put your station at, so long as you are not in a production house that has to follow strict standards of +/- 5% to a calibrated traceable thermometer!

author: sparkypom
author_rank: Contributor
timestamp: February 09, 2012, 07:58:55 pm
content: Quote from: saturation on February 08, 2012, 08:43:21 pmWhat you say about immersion in the solder makes sense and is how Edsyn do it, but their calibration kit would cost me over US $600 including taxA Fluke UK tech told me that what I suggested would work though I did not get much detailed info from him. The Fluke thermocouple probe 80pk-26 is supposed to be good for surface and air measurement and the datasheet says "Even though the sheath to junction transition is sealed, it is not recommended to immerse the probe in liquid or saturated vapor." That makes me think that there is some kind of insulating junction between the tip (which is about 1.57mm diameter and 11mm long) and the sheath, but that is only my guess. But then it says later that the probe should be inserted at least 6.35 cm into the environment to be measured to minimize the shunting effect of the sheath, but I guess that must apply to air measurement. So I am not sure about shunting effects for surface measurement. They say the accuracy is +/- 0.75% above 293 degrees C and +/- 2.2 degrees C below it and being Fluke, you would think that this should work. i.e. if the probe is designed for surface measurement, I would think that they take the shunting into account in the design. They suggest using silicon grease to get a better contact with the surface and maybe using a small amount of solder would actually give worse results - I don't know. Would silicon grease cause any problems with the tip?Anyway, just looking at the practicalities, pressing a 12 inch long thermocouple probe with a 1.57mm bead tip against a 1.5mm soldering iron tip would be tricky. The iron or probe would have to held very firmly in some kind of rig I think. Also the parts I mentioned would cost about $250. The Hakko tip thermometer only costs about $10 less than that in the UK with 10 elements but I wouldn't trust it as a long term solution. They even charge an extra $50 for a calibration certificate. What a ripoffI think what you suggested seems like a great way to calibrate any cheap soldering station and I am beginning to think it is the best way forward. It might cost a bit to get various different solders and maybe there would also be a slight shunting effect to take into account but looking at this listhttp://www.rfcafe.com/references/electrical/solder.htmthere seem to be a wide range of solders with different melting points.Spread the word

author: IanB
author_rank: Super Contributor
timestamp: February 09, 2012, 08:04:19 pm
content: Quote from: sparkypom on February 09, 2012, 07:58:55 pmI think the technique would be to lay the thermocouple on a soft, insulating, heat resistant surface and then press the tip of the iron down on top of it. I'm not sure what the best insulating surface would be--silicone rubber, perhaps? I have a silicone rubber skillet at home that is theoretically able to withstand hot dishes from the oven, so I might check that with my iron to see how temperature resistant it is.

author: Rufus
author_rank: Super Contributor
timestamp: February 09, 2012, 09:28:45 pm
content: Quote from: saturation on February 08, 2012, 08:43:21 pmAnd the same effect but more so occurs while soldering anything so exactly what are you calibrating and what is the point?I have never had any interest in calibrating soldering irons because I have never had any interest in the absolute number set or read from a display. It is mostly QA bullshit, they demand to know exactly what the temperature is but couldn't tell you what it is supposed to be.

author: nanofrog
author_rank: Super Contributor
timestamp: February 09, 2012, 10:12:16 pm
content: Quote from: saturation on February 08, 2012, 08:43:21 pmThe "cheap ones" I've seen on eBay are going for ~$50USD or so ATM, but found it a bit cheaper @ ~$28USD from here:http://www.bestofferbuy.com/lodestar-soldering-iron-tip-digital-sensor-thermometer-p-8114.html. Not going to break the bank by any means, but the price does seem to be climbing on eBay. Seems a bit pricey for what they are IMO, but that may just be me.So if you know of a less expensive source (i.e. I searched the wrong term to locate those gems), links would truly be appreciated.I'd be nervous of most of the K type thermocouples that typically come with meters, as most are rated for ~200C searching around (based on the insulation used from what I understand). So I've been toying with the idea of using a CP01 from Weller (http://www.all-spec.com/products/CP01.html) directly on the meter (use the tilt feature + Mini K to Banana jack adapter I already have to get enough distance that molten solder won't land on the meter and burn it).Not much of a cost difference, but I won't have to wait as long to get it in the mail. And if I want to get fancy, it should be reasonably easy to rig up a project box with a metal lid + panel mount Mini K connector and a pair of female banana's to make a solder temp test jig that uses the Weller K type, and not have to worry about molten solder ever coming into contact with the plastic face of the meter. Hakko's sensors should be doable too, but a bit more complicated (need to make the posts <nylon shoulder washers & M3/M4 machine screws or even solder turrets maybe?> and a tensioning mechanism).But it should definitely be possible to get actual temps without making one's wallet squeal in pain.Quote from: sparkypom on February 09, 2012, 07:58:55 pmI'd think it's to help prevent corrosion, which could cause inaccurate readings (or none at all).Quote from: IanB on February 09, 2012, 08:04:19 pmFrom what I've seen of the commercial units, most are done in free air (i.e. Hakko, Weller). Palmer Wahl attaches their sensor to a ceramic disk from what I can tell from photos (not sure if there's a recess to create an air gap between it and the ceramic though).As per silicone rubber, it's usually specified between 500 - 600F (260 - 316C) from what I've seen, so it would be able to withstand leaded solder. I wouldn't try it with the station on max (typically rated at 450C/842F max).

author: amyk
author_rank: Super Contributor
timestamp: February 10, 2012, 10:51:07 am
content: Quote from: nanofrog on February 09, 2012, 10:12:16 pmFake 191s, they're still selling them:http://www.ebay.com/itm/Tip-Thermometer-Solder-Iron-Tip-Digital-Tester-HAKKO191-/180675527416?pt=LH_DefaultDomain_0&hash=item2a1119c2f8(Fromhttps://www.eevblog.com/forum/general-chat/do-you-calibrate-your-soldering-station-if-not-or-if-so-why/15/- I notice from the inside pictures of the IC pinout that it seems to use the same ICL7106 A/D bare-die as the ultra-cheap multimeters - which not surprisingly often have temperature measurement capability using K thermocouples.)

author: nanofrog
author_rank: Super Contributor
timestamp: February 10, 2012, 11:30:11 am
content: It had already ended when I checked.Though at that price I expect they'd go quick, so it's likely I'm just not finding them in time to snag one (even with shipping, it's cheaper than the K type I've been looking at).

author: saturation
author_rank: Super Contributor
timestamp: February 10, 2012, 12:22:08 pm
content: You mean the eutectic solder? Yes, its simple because the solder is acting like a thermometer. Recall, all you need to do is match one point in the scale to get the whole scale 'aligned', you do not need to sample other points in the scale as its only approximate.Quote from: sparkypom on February 09, 2012, 07:58:55 pm

author: saturation
author_rank: Super Contributor
timestamp: February 10, 2012, 12:27:58 pm
content: The point is simply insuring the tip and the scale on your station are in sync. Some thermocouple sheaths are large and will serve like a huge ground plane. So it will take longer to obtain thermal equilibrium to make your measurement, if at all.As to why you should calibrate your station, has been discussed on the archives, just search my name and the topic. You needn't get anal about being in IPC standards, all you need to know is where the 350C mark is, which is the magic number for soldering efficiency. If you know that, then you'll pretty much know the whole scale too.Quote from: Rufus on February 09, 2012, 09:28:45 pm

author: sparkypom
author_rank: Contributor
timestamp: February 10, 2012, 08:14:59 pm
content: Quote from: saturation on February 10, 2012, 12:27:58 pmI think there would be a bit more to it that. That 350C point takes into account heat shunting from a circuit being soldered and I have not found any eutectic solder with a melting point of 350C or even near. it. Even then, there may be non-linearity over the range and you might want to go down to 280C or so for heat sensitive devices.Ideally I think it would be better to use samples of solder with a range of melting points preferably between 280C to as high as you can - but maybe a good enough approximation would be to melt a small piece of eutectic solder with a melting point in the middle of the range i.e. about 320C and then turn the temp down slowly till it solidifies. The highest melting point I have found so far (http://www.aimalloys.com/solder_chart.htm) is 309C (Pb97 - 97.5% Lead, 1.5% Silver and 1% Tin) which might be ok.

author: sparkypom
author_rank: Contributor
timestamp: February 10, 2012, 09:40:09 pm
content: I found some solder on the Indium Corporation website that cover the range but we are talking really silly money hereIndalloy number 202 (Melting point 266C 82.6 Cadmium 17.4% Zinc)Indalloy number 182 (Melting point 280C 80% Gold 20% Silver)Indalloy number 239 (Melting point 313C with 91% Lead, 4.0% Tin, 4.0% Silver and 1% Indium)Indalloy number 183 (Melting point 356C with 88% Gold, 12.0% Germanium)Indalloy number 176 (Melting point 382C with 95% Zinc 5% Aluminium)Also note that eutectic alloys do not necessarily solidify and liquefy at the same temperature though these ones do.In the end the idea turns out to be a dead duck I'm afraid and probably not just because of the crazy cost of solder that can melt at the right temperature range.Back to the drawing board !

author: IanB
author_rank: Super Contributor
timestamp: February 10, 2012, 10:10:30 pm
content: Quote from: sparkypom on February 10, 2012, 09:40:09 pmThis is odd since the definition of a eutectic alloy is a single sharply defined solid/liquid transition point. Is it because the solid alloy contains grains of non-eutectic composition that melt at different temperatures?

author: sparkypom
author_rank: Contributor
timestamp: February 11, 2012, 09:35:40 am
content: Quote from: IanB on February 10, 2012, 10:10:30 pmI think I may have got that wrong. My head was spinning after looking at a load of different webpages and I made an incorrect assumption after watching Dave's soldering blog because I found some 63/37 solder that doesn't have a single transition point -http://www.rapidonline.com/Tools-Equipment/Rosin-free-Omega-63-37-solder-28723/?sid=b683244e-c7f7-4f8c-8de4-ee518b5c8e01.Having said that I keep finding mistakes on Rapid's website so maybe that is wrong too !I was wondering at the time what the E next to the liquidus colum meant on this Indium datasheethttp://www.indium.com/products/alloy_sorted_by_temperature.pdfand in the clarity of the morning it seems obvious that it must stand for eutectic

author: IanB
author_rank: Super Contributor
timestamp: February 11, 2012, 09:46:55 am
content: Quote from: sparkypom on February 11, 2012, 09:35:40 amHmm, it says "Solder content: 63% tin, 37% lead; Melting point 183°C-185°C"I'd guess that 2 degree variation is most likely due to manufacturing tolerances. For practical purposes you would experience that as a single temperature when working with it.

author: saturation
author_rank: Super Contributor
timestamp: February 11, 2012, 12:49:02 pm
content: While not the ideal lead free solder, SnCu 99:1, 227C precise and dirt cheap.