more accurate or more efficient heat transfer to the thermocouple?
What are the main differences between a grounded and ungrounded thermocouple?
Grounded thermocouple: This type of temperature measurement device has the advantage of more efficient heat transfer. With the junction welded to the metal sheath, a grounded thermocouple will respond faster to temperature changes because the metal-to-metal contact creates a shorter thermal pathway compared to an ungrounded thermocouple. However, this grounding can create an undesirable side effect. By welding the junction to the sheath, an electrical connection is also made between the wires and the sheath. This can lead to a “ground loop” if the sensor is connected to earth ground at the point of measurement and if the wires are connected to a controller, which is grounded in another location. The two grounds may not be at the same voltage potential, thus creating an undesired circuit that may damage equipment. Ungrounded thermocouple: An ungrounded thermocouple is not welded to the metal sheath and typically has nonconductive powder, like magnesium oxide, surrounding the junction at the sensor’s tip. This material slows the thermal transfer from the media being measured to the junction of the thermocouple. Because the thermocouple wire is electrically isolated from the metal sheath and case, using an ungrounded thermocouple reduces the risk of ground loops.