Enhanced Range With Extending Thermocouple Wires

Thermocouple wires have their own set of restrictions due to noise and ground loops; by taking certain precautions you can expand their range. At IOThrifty we offer color-coded extension grade thermocouple wire which meets ANSI MC96.1 standard for easier monitoring of range.

Type K cables are popular due to their broad temperature range and superior oxidation resistance. By comparison, types R and S cables crafted from noble metals may become contaminated in reduced environments.

Length

Thermocouples are simple temperature measurement sensors made from two dissimilar metals that produce an electric current which correlates with temperature. Since thermocouples contain specialized alloys, care should be taken when extending them.

General rule of thumb dictates that 20 AWG or thicker wire in an area free from electromagnetic interference usually works just fine for thermocouple signal monitoring applications. There are various factors which affect usable length; two key ones being loop resistance and noise interference with thermocouple signal.

Connectors are used to minimize noise interference from thermocouple extension wires and eliminate interference with their signal. Each thermocouple connector type features its own configuration that caters specifically to that type of thermocouple; typically these will include loose ends to facilitate quick terminal connection as well as some form of locking mechanism for added security, plus terminal blocks or connectors that plug directly into its head itself.

Resistance

Thermocouple wires consist of two different metal alloys which generate a small voltage when exposed to changing temperatures, which is then converted into temperature measurements using standard calculations.

An accurate result depends on selecting the ideal thermocouple wire type. Reputable manufacturers provide selection guides that assist customers in making this selection decision.

An additional way to increase thermocouple accuracy is using extension wire with Special Limits of Error (SLE) specifications. These types of wire use purer forms of alloys commonly found in thermocouples to provide improved accuracy specifications compared to regular cable.

When connecting an extension wire to your sensor, make sure it matches both the type and polarities of its thermocouple counterpart. Also use a terminal block made from metal similar to both devices for ultimate noise suppression during measurements. This prevents unwanted electrical noise from corrupting your measurements.

Noise

Thermocouples provide an effective means of monitoring fluid temperatures, but you must know which type will suit your application best. When making this choice, take into account both your monitoring range and accuracy requirements; then select either wire or probe style sensors depending on which will best serve your purposes.

Thermocouple sensors produce an electrical, or thermoelectric, signal based on the temperature difference between hot and cold junctions of two dissimilar metal conductors – this phenomenon is known as The Seebeck Effect.

Electrical interference along the length of a wire can significantly disrupt its signal and introduce error into measurements, so keeping extension wires away from power lines, motors, and other electrical devices helps minimize this noise. Furthermore, installing a 10nF differential capacitor between positive and negative leads near an artificial cold junction helps minimize noise on long wire runs.

Ground Loops

Ground loops occur due to improper wiring practices, malfunctioning equipment or natural current flows in the Earth; they may introduce unwanted current into thermocouple circuits leading to inaccurate temperature readings.

One common ground loop issue involves using copper wire to extend thermocouple sensors, creating two new dissimilar metal junctions which must be adjusted through your controller software. Furthermore, different alloys for extension wire conductors increase error in your system further.

To prevent ground loops, all thermocouple extension wire must be made from the same alloy as its sensor. At IOthrifty we offer an assortment of thermocouple extension wire that adheres to standard limits of error set forth by ANSI C96.1* and comply with its standard limits of error requirements.