Temperture shown at printer display Not always correct !

Using a calibrated digital thermometer, attached to nozzles,
we found that right-nozzle averaged about 14 C Hotter than temp displayed at printer:(
and left-nozzle averaged about 6 C Hotter than displayed.

So, we lowered Temp setting in Host/slicer software by those amounts
and printed objects were much better. :D

Not sure if error is caused by Thermocouple-wires or the Motherboard circuit.
Maybe someday I'll replace T-wires to determine if they cause it.

Note: Bed-plate temp, on top of added glass, averaged about 12 C cooler than Indicated temp at display.
The Fan cooling X & Y stepper-motors is probably cooling the glass.

This is the Second time we have done this Temp testing.
First time was about a month ago and results were very similar then.

We have been operating at revised temp settings since that first test. :)

It is quite normal for cheap thermocouple circuits to not include the reference measurement. This means that ambient temperature variation is not accounted for.

A thermocouple is only a difference between two junctions, it cannot function accurately on its own.

Temperature for printing should never be chosen by looking at the temperature reading other than initial rough setting, it should always be chosen depending on results.

Yes, too many people are relying on the displayed temp to be accurate,
and it's probably Not, in most 3Dprinters.