| ACCESSORIES |
 |
|
 |
| |
|
|
 |
| |
| THERMOCOUPLE DESCRIPTION |
|
|
A thermocouple is a sensor for measuring temperature. It consists of two dissimilar metals, joined together at one end, which produce a small unique voltage at a given temperature. This voltage is measured and interpreted by a thermocouple thermometer. |
| |
| THERMOCOUPLE TYPES |
|
|
Thermocouples are available in different combinations of metals or calibrations. The four most common calibrations are J, K, T and E. Each calibration has a different temperature range and environment, although the maximum temperature varies with the diameter of the wire used in the thermocouple.
|
| |
| HOW DO I CHOOSE A THERMOCOUPLE TYPE? |
|
|
Because thermocouples measure in wide temperature ranges and can be relatively rugged, they are very often used in industry. The following criteria are used in selecting a thermocouple |
|
|
|
|
 |
Temperature range |
|
Abrasion and vibration resistance |
|
Installation requirements (may need to be compatible |
|
Chemical resistance of the thermocouple or sheath |
| |
with existing equipment; existing holes may determine probe diameter). |
|
material |
|
| |
| HOW DO I KNOW WHICH THERMOCOUPLE JUNCTION TYPE TO CHOOSE? |
|
|
 |
 |
 |
| Grounded |
Ungrounded |
Exposed |
|
|
Sheathed thermocouple probes are available with one of three junction types: grounded, ungrounded or exposed. At the tip of a grounded junction probe, the thermocouple wires are physically attached to the inside of the probe wall. This results in good heat transfer from the outside, through the probe wall to the thermocouple junction. In an ungrounded probe, the thermocouple junction is detached from the probe wall. Response time is slowed down from the grounded style, but the ungrounded offers electrical isolation of 1.5 M1/2 at 500 Vdc in all diameters. The thermocouple in the exposed junction style protrudes out of the tip of the sheath and is exposed to the surrounding environment. This type offers the best response time, but is limited in use to noncorrosive and nonpressurized applications. See the illustrations at the right for a full discussion of junction types. |
| |
|
| |
