What is a thermocouple wire and how does it work?

Take a look at the thermocouple wire today.

What is a thermocouple?

A thermocouple is a temperature-measuring element commonly used in temperature-measuring instruments.

Usually by the heating electrode, insulation sleeve protection tube junction box, and other major components, usually display instruments, recording instruments, and electronic regulator supporting the use.

In the industrial production process, temperature is one of the important parameters to be measured and controlled.

In temperature measurement, the thermocouple application is extremely wide.

Its advantages include simple structure, convenient manufacture, wide measuring range, high precision, small inertia, and output signal for remote transmission.

In addition, because the thermocouple is a passive sensor, measurement without an external power supply, is very convenient to use.

So it is often used to measure the temperature of gas or liquid in the furnace, or pipeline, and the surface temperature of solids.

Thermocouple Cable:

A thermocouple cable is a wire used in a thermocouple between the sensing point and the cold end compensation point where the signal is measured.

Since thermocouples are made of two different metals joined at the sensing end.

Different types of thermocouples such as J, K, T, E, etc. use different combinations of metal wires.

At the cold end compensation end, the millivolt value provided by the thermocouple indicates the temperature difference between the sensing end and the cold end compensation end.

How do I recognize insulated thermocouple wire?

The color coding of its insulation identifies the thermocouple wire.

1 The negative lead in the insulated thermocouple compensation wire is red.

2 The positive lead is the same color as the compensation wire.

3 The jacket of the thermocouple wire is usually brown.

4 The high-temperature wire is usually white.

About more, you can consult ZMSKVCABLE, We will provide you with a wire insulation marking table and so on.

What is the difference between standard and special error limits?

Standard and special error limits are related to the accuracy of the wire.

Special error-limiting wires are the same as standard error-limiting wires but have a higher degree of accuracy.

The accuracy of thermocouples varies with the type of thermocouple.

For example, the lower temperature range Type T, which consists of a positive copper wire and a negative con copper (copper-nickel blend), has good accuracy specifications.

What is the difference between thermocouple wire and compensation wire?

Thermocouple wire is the wire used to create the thermocouple induction point.

Compensating wire is only used to extend the thermocouple signal to the instrument that reads this signal.

Compensation cable usually has a lower ambient temperature limit.

That is, it can carry a signal from a probe at a higher temperature, but it is not itself exposed to the higher temperature.

Thermocouple wire can be used as compensation lead, but compensation lead cannot be used to create a thermocouple sense point.

The compensating wire is usually given a part number that begins with the prefix “EX”.

Difference between RTD cables and thermocouple cables

About Thermocouple Compensating Cables

Compensating cables are used to extend the cold end of multi-point hot electrodes and mobile thermocouples to be connected with display instruments to form a multi-point temperature measurement system.

The measuring end is the hot end, and the end connected to the measuring circuit through the lead is called the cold end.

Compensation wire using insulation and sheath selection of imported high-quality fluorine plastic.

The use of the whole continuous extrusion process, so that the product has excellent resistance to acid, and alkali, wear-resistant and non-flammable performance, and can be immersed in oil and water for long-term use.

Compensating cable using temperatures of -60-260 ℃, belongs to the contemporary international advanced level.

Thermocouple compensation cable is suitable for electric power, metallurgy, petroleum, chemical industry, textile, and other industries, as well as national defense, scientific research, and other sectors of the automated temperature measurement instrumentation of multi-point connection.

RTD cable

This kind of cable uses ZR-DJFPGP or ZR-DJYPVP (1×3×1.0).

Where ZR-flame retardant, DJ-computer cable, FP-polybutadiene shielding, GP-communication.

Why use a 3-core cable for RTD?

The reason is as follows.

There are two-wire, three-wire, and four-wire systems for RTDs.

The resistance of the two-wire cable itself will interfere with the measurement results, Three-wire and four-wire systems is to add a bridge, used to compensate for the cable resistance, and the measurement results are more accurate.

Armored thermocouple wire

Armored thermocouple cable is commonly known as armored wire, also known internationally as inorganic insulation thermocouple cable.

It is a solid whole made of stainless steel protection tube, magnesium oxide insulating powder, and thermocouple wire material combined and compacted by mold. It has the advantages of pressure resistance, shock resistance, flexibility, miniaturization, fast thermal response time, etc. It is the core material for manufacturing armored thermocouples.

Qualified armored thermocouple cable should be in the factory before the constant temperature box above 200 ℃ after sufficient moisture.

Both ends are sealed with epoxy resin, which can ensure the insulation resistance of the cable.

When armored thermocouple cable is used, it is generally cut into multiple sections, resulting in magnesium oxide insulation powder exposed to the air. And magnesium oxide powder has strong hygroscopicity, which is bound to have a lot of moisture in the air into the magnesium oxide.

This caused a drop in insulation resistance, affecting the accuracy of high-temperature measurements.

For this reason, it is recommended that in the process of making armored thermocouples. When the hot end of the sealing and welding is completed and the cold end of the measuring wire is stripped out the whole thermocouple should be placed in a constant temperature box of 200 ~ 250 ℃ to drain the moisture for 12 ~ 24 hours.

For thermocouple cables under one meter in length, the temperature and time can be reduced accordingly.

Then take out and quickly seal with epoxy resin. Unused armored thermocouple cables should also be immediately sealed with epoxy resin for the next use.

The above is a detailed introduction to the thermocouple cable, if you have any questions when buying, you can consult us.