Calibration inspection How-To for all External Soldering iron thermometer

[Kiriakos GR]

Welcome in the world of External Soldering iron thermometer.
Do not guess it but believe it, that you do not know anything about them.

Hakko (Japan) at the year 8/2000 and later succeed to present at the market the basic design of External Soldering iron thermometer.
This style of thermometer with the triangular shape of sensor  (K-Type thermocouple) soon become a measurement standard = one apparatus that it can be trusted internationally.   

But this triangular shape of sensor (K-Type thermocouple) this has it own secrets.
A regular and full in length K-Type thermocouple this is capable to deliver an output of several mV DC.
The sort version ( triangular shape of sensor ) it cannot deliver enough amount of mV DC if this is not heated enough.

In theory, the sensor 191-212, this has starting point of operation the 50 Celsius.
But it true operation range this is 100~600C, and therefore we can trust only the reading within this range.

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From the side of the side of the Unit Thermometer identical laws apply.
The thermometer it can not function properly if it does not receive from the sensor a minimum amount of DC millivolts.

At the process of calibration inspection, the voltage source which substitutes the thermocouple, at 100C setting this must deliver 4,20mV DC.
The temperature measurement will now include 100C plus the value of Room temperate (example 18C), and the real total will be at 118 Celsius.

Therefore if we think of the thermometer unit as to be an mV DC measuring device, the actual input range this is 4.20 mV up to 24.92 mV.    
24.92 mV this is equal at sensor output for 600 Celsius, and actual expected measurement, this will also include Room temperature, so actual and correct reading will be 618 Celsius.

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Temperature calibration this does not translate to thermometer circuit fine adjustment.
But instead of us to determine the measuring error of its thermometer at it entire range.

A new tool it is now required for thermometer inspection, and this is no other than one adjustable voltage source ( portable DC volt source ), this including a very detailed range of adjustment.

Time Electronics 1048,  this is a good choice of required tool, so us to explore thermocouple output range  of -200 ~ 1372 Celsius.
That is the range of processional K-type thermometer.

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I you are owner of any budget price of External Soldering iron thermometer,  you can still inspect your meter if you own a serious analog DC power supply with Fine-Coarse function.
And or a digitally programmable power supply of some value.
In both cases, you will not have any detailed stepping of adjustment, but at least you will have a basic way to confirm if your thermometer this is significantly out of calibration.


Calibration inspection at usable soldering iron range of temperatures, this is of highest importance.
Rule of thump:
mV setting
12,207 mV = 300C with included your room temperature (screen measurement will be 318C)
16,395 mV = 400C with included your room temperature (screen measurement will be 418C )
20,640 mV = 500C with included your room temperature (screen measurement will be 518C )

[Kiriakos GR]

Rule of thump about soldering station temperature adjustment :

leaded solder
Melting point                     419°F  (215°C)
 
Normal operation              518°F-572°F  (270°C-300°C)

Production line operation  608°F-716°F  (320°C-380°C)

Desoldering operation for small joint 599°F (315°C)
Desoldering operation for larger joint 752°F (400°C)


lead-free
Melting point                           220°C (428°F)

Normal Operation                   300-360°C (572-680°F)
Production Line Operation      360-410°C (680-770°F)

A good joint is assured if the iron's operating temperature is set within the parameters suitable for the
type of solder being used.
The solder will flow too slowly if the temperature is too low.
If the temperature is too high, the flux in the solder may burn which will give rise to billowing white smoke.
In turn, this will result in a dry joint or in permanent damage to the PCB. 

[Kiriakos GR]

Here I have an alternative suggestion for the ones whom own all ready a high quality HH DMM.

K-Type thermocouple output this is at mV DC range, and it must reviewed at five digits resolution.
Time Electronics 1030 Microcal while this is older and analog calibrator, this has also two prefix output at mV range.
0.0 ~10 mV and 0.0 ~100 mV.

While there is analog type of adjustment, with ten turn knob (potentiometer), you may explore ITS-90 Table for Type K Thermocouple with very good definition up to 247 Celsius = 9.995 mV + room temperature (18C) the thermometer will read 264C.

[overvolt]

Interesting topic but not for lightweight hobbyist. 

[Kiriakos GR]

Interesting topic but not for lightweight hobbyist. 

Digital Thermometer Calibration inspection, this never was easy for anyone to play with.

The High-End portable calibrators they come with retail price of 2000 ~ 3000 Euro.
Yokogawa 2422 this is what Hakko trusted at the date of 8/2000 when they present their HAKKO 191, which is today totally outdated.
Yokogawa 2422 output 0.1mV ~ 30V
Range: 1mV , 10 mV, 100 mV, 1V, 10V, 30V

(FG-100 (Date 2011)  and newer has better electronics and ten times better ergonomic design.)