Five major issues to be aware of thermocouple compensation wires
The five major issues that need to be paid attention to during the use of thermocouple compensation wires
Contact connection
As close as possible to the two contacts of the thermocouple terminal, try to keep the temperature of the two contacts consistent. The temperature is the same as the temperature at the junction of the meter terminal. Where the instrument cabinet has a fan, the contact point should be protected from blowing the fan straight to the contact point.
2. Compensation wire selection
The compensation wire must be correctly selected according to the type of thermocouple used and the occasion used. For example, the k-type couple should select the compensation conductor of the k-type even, and select the operating temperature range according to the application. Usually, the kx operating temperature is 0 to 1200 ° C, and the wide range is 0 to 1300 ° C. The normal level error is ±2.5 °C and the precision level is ±1.5 °C.
3. Wiring
The compensation wire routing must be kept away from the power line and the interference source. In places where it is not possible to avoid crossing, use crossover as much as possible, not parallel.
4. Shielding compensation wire
5. Use length
Because the signal of the thermocouple is very low, it is microvolt level. If the distance used is too long, the attenuation of the signal and the interference of strong electric current in the environment can make the signal of the thermocouple distorted, resulting in inaccurate measurement and control temperature. Temperature fluctuations occur when the control is severe.
According to our experience, it is usually better to use the thermocouple compensation wire length control within 15 meters. If it exceeds 15 meters, it is recommended to use a temperature transmitter to transmit signals. The temperature transmitter converts the potential value corresponding to the temperature into a DC current transmission, which is strong against interference.
Bimetal thermometers work on the principle that two different metals expand differently when the temperature changes. The main component of an industrial bimetal thermometer is a multilayer metal sheet that is laminated with two or more metal sheets. In order to improve the sensitivity of temperature measurement, the metal sheet is usually formed into a spiral shape. When the temperature of the multilayer metal sheet is changed, the amount of expansion or contraction of the metal of each layer is not equal, so that the spiral wound is rolled up or loosened. Since the end of the spiral coil is fixed and the other end is connected to a freely rotatable hand, when the bimetal feels a temperature change, the pointer can indicate the temperature on a circular indexing scale. The temperature range of this meter is 200~650°C, and the allowable error is about 1% of the two steps of the scale. This thermometer is similar in use to a rod-shaped glass liquid thermometer, but can be used under conditions requiring higher mechanical strength.