What is effect of Thermocouple performance by element length and wire diameter?
There are two thermocouple "K" type Cr-Al junction. One of them have wire Diameter 1.5 sq mm and other of 2.5 Sq mm. Even the length of the element is 400 mm and other 425.
Neither the wire length nor the wire diameter have any effect on performance. The meter measures emf, which is not affected by either of these.
What DOES affect performance is purity of the wire. If some other substance is present in, say, the chromel, then it acts as a thermocouple itself, giving an error. The critical part of the wire is the part subjected to the thermal gradient.
The emf is not generated in th ejunction, but rather in the thermal gradient area of the wire. The junction simply serves to connect the two wires together electrically.
November 29th, 2009 at 5:06 pm
Neither the wire length nor the wire diameter have any effect on performance. The meter measures emf, which is not affected by either of these.
What DOES affect performance is purity of the wire. If some other substance is present in, say, the chromel, then it acts as a thermocouple itself, giving an error. The critical part of the wire is the part subjected to the thermal gradient.
The emf is not generated in th ejunction, but rather in the thermal gradient area of the wire. The junction simply serves to connect the two wires together electrically.
References :
November 29th, 2009 at 5:37 pm
The thermal conductivity of the wire is proportional to the cross sectional area so could affect slightly the junction temperature.
The thermal mass of wire changes the speed of response.
References :