TuKas rašė:

> o kad termopora veiktų, bet imtų rodyti neteisingai, tikimybė labai
> maža. Įtariu, kad problema matavimo keitiklyje, kurį ir tikrinčiau
> pirmiausia.

http://tcomega.com/temperature/Z/pdf/z021-032.pdf

„Decalibration is a far more serious fault condition than
the open thermocouple because it can result in a
temperature reading that appears to be correct.
Decalibration describes the process of unintentionally
altering the physical makeup of the thermocouple wire
so that it no longer conforms to the NBS polynomial
within specified limits. Decalibration can result from
diffusion of atmospheric particles into the metal caused
by temperature extremes. It can be caused by high
temperature annealing or by cold-working the metal, an
effect that can occur when the wire is drawn through a
conduit or strained by rough handling or vibration.
Annealing can occur within the section of wire that
undergoes a temperature gradient.“

<...>

In a typical thermocouple installation there are several modes of 
failure but four modes are somewhat common. These common failure modes are:
     *
           o 1) degradation of the weld joining the two metals at the 
hot end,
           o 2) degradation of either metal leg due to chemical or 
metallurgical changes occurring at high temperatures,
           o 3) degradation of the electrical connection between the 
instrumentation to the thermocouple, and
           o 4) secondary junctions caused by degradation of the 
electrical insulation between the two thermoelements away from the hot end.