Products > Test Equipment
Measuring the temperature of a soldering iron tip
JimKnopf:
I also bought recently a FG-100 clone from ali like @smbaker mentioned in this post.
https://www.eevblog.com/forum/testgear/measuring-the-temperature-of-a-soldering-iron-tip/msg4765436/#msg4765436
The reason was i managed to get some parts in my JBC CD-2SQE exploded while soldering on a board connected to main power line but switched off. Unfortunally is was one of the usual single line switches, so live line and mains earth from soldering station meet in my JBC board. The device was still starting and displayed temp values but could not heat the tips. I repaired some parts using schematics i found here on eevblog (https://www.eevblog.com/forum/testgear/jbc-soldering-station-cd-2bc-complete-schematic-analysis/). After that it heats up but i was not sure if the temperature was correct. I've got a Keithley DMM6500 and a K-Thermocouple temperature sensor for it. It's a very accurate measurement. But it's tricky to find the right angle/position for a correct reading with a solderiron tip. So i gave the FG-100 a try.
The FG-100 clone shows very low temperature. I mean 3% difference would be ok, or maybe 5% is accetable. But it's missing around 40 to 50°C. I tested with a Pinecil V2, JBC CD-2SQE and a JBC clone, my new Jabe UD-1200 PRO (only T210 handle).
The repaired JBC CD-2SQE was set to 330°C which i measured exactly with the Keithley DMM6500. The FG-100 clone showed something around 282-284°C max.
The Pinecil was set to 410°C which i measured exactly at this temp with the Keithley DMM6500. The FG-100 clone showed something around 372°C. The FG-100 looks like useless. It's total crap. I opend the device because i read some could be calibreated. Seems i got the cheapest one on earth with missing parts. There is a printed mark "VR1" with 1K on the PCB. But the parts in this area are missing.
Anyone figured out what resistors are needed to get the calibration circuit to work? Looks like 2 resistors with unknown values are missing.
wraper:
--- Quote from: JimKnopf on August 20, 2023, 07:07:38 pm ---Anyone figured out what resistors are needed to get the calibration circuit to work? Looks like 2 resistors with unknown values are missing.
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It looks quite straightforward. You need to remove R1 and populate R10, R9 and VR1 which apparently should be 1k. You should select R10 and R9 in a way so total resistance in the middle position of VR1 is about the same as R1 which is 9.31K. So you could populate two 4.3k Resistors + 1k multi turn potentiometer. In a case if you don't have enough adjustment range to get proper reading, replace one of the resistors to a little bit higher or lower value. Of course there is no guarantee it work correctly as normally there should be separate adjustments for gain and offset but you can try and see if it gives an acceptable result.
KungFuJosh:
Two things to also consider regarding accuracy: the tip sensors are disposable, and can only accurately measure a limited amount of times. It is also sometimes helpful to use a drop of solder as a heat bridge.
DaneLaw:
Tried some years back to take soldering iron temp-readings with both thermal & these surprisingly cheap FG100 clones.
Overall pleasantly surprised about these 8 dollar Chinese clones on eBay, though it's like almost a decade back.
Were both fast and surprisingly accurate for the price, the biggest con was misplacing the spare sensors that came bundled.(no idea where mine is)
The blue unit at the left (FG-100)..though soldering irons on thermal-macroshots is more helpful to sense variables on the heating area' than to give tangible ref values.
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wraper:
--- Quote from: KungFuJosh on August 21, 2023, 02:45:33 am ---Two things to also consider regarding accuracy: the tip sensors are disposable, and can only accurately measure a limited amount of times. It is also sometimes helpful to use a drop of solder as a heat bridge.
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Not just helpful, a blob of solder on the tip is mandatory for accurate measurement.
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