What impact does the temperature of K-type compensation wire have on T-type thermocouples?

I’m not sure what specific value will be displayed, or whether it will be higher or lower than the actual value. However, I know that the temperature value shown definitely won’t correspond to any standard scale. I have dealt with similar issues before: a K-type thermocouple was connected to a compensation cable designed for the T scale, which caused the temperature readings to become incorrect. The readings seemed to be close to those of the J scale, but the difference was significant.

The mV values of T-type and K-type thermocouples within the 50°C range are quite similar; according to the calibration tables, there is a difference of around 0.4°C, with the T-type thermocouple having a slightly higher mV value, which results in a slightly higher displayed temperature.

2. The incorrect type of compensation wire is being used (taking K-type thermocouples as an example). The same type of compensation wire should be used with the same type of thermocouple; if the wrong type of compensation wire is chosen, errors will still occur. Assuming an S-type thermocouple is used, and the compensation wire Kx for a K-type thermocouple is selected, then according to the intermediate conductor law, the total thermoelectric potential received by the instrument is E′total(t1,t2) = es(t1,t3) + ekx(t3,t2) (5). If the proper compensation wire SC for an S-type thermocouple is used, and ignoring any errors in the compensation wire itself, the total thermoelectric potential measured by the instrument is Etotal(t1,t2) = es(t1,t3) + es(t3,t2) (6). Due to the incorrect selection of the compensation wire, the error in the instrument’s measurement is given by equation (5) minus equation (6), that is, E′total – Etotal = es(t1,t3) + ekx(t3,t2) – es(t1,t3) – es(t3,t2) = ekx(t3,t2) – es(t3,t2). If the operating temperature of the S-type thermocouple is 900°C, and assuming t3 – t2 = 8°C, the potential difference can be determined by referring to the calibration tables for both S-type and K-type thermocouples; this results in ekx(t3,t2) – es(t3,t2) = 0.278 mV. This indicates that the temperature measured by the instrument is higher than the actual temperature. If the instrument indicates 900°C, the actual temperature is only 875°C, resulting in an error of about 25°C. If the polarity is reversed under the aforementioned conditions, the instrument reading will be too high; that is, when the instrument shows 900°C, the actual temperature is 933°C, resulting in an error of about 33°C.