2013 Volume 31 Issue 3 Pages 208-215
K-type thermocouples are fabricated using a chromel wire and an alumel wire of 50&mu:m by non-contact discharge welding method. The welding is carried out at six different butt angles. The size of hot junction tends to decrease with an increase in butt angle, when the butt angle is larger than 1.4rad. The response rate is measured and it is almost proportional to reciprocal of the size of hot junction. It is shown that the size of hot junction is an important factor for response rate. Wire diameter is another important factor for temperature measurement of small objects. When temperature is measured at a same point by a thermocouple under the condition that only hot junction and its vicinity are heated, the output of electromotive force, i.e., indicated temperature will depend on the wire diameter. As the metal wire is good thermal conductor and the rate of heat transport is proportional to the area of wire cross section, deviation from true value increases with an increase in wire diameter. Our experiments showed that the indicated temperature decreased linearly with the wire diameter. Furthermore, we measured the discharge voltage and current at various setting current and discharge gap.
