Matters needing attention in the use of compensation wire
1. Selection of compensation wire Compensation wire must be correctly selected according to the type of thermocouple used and the occasion used. For example, K-type couple should choose the compensation wire of K-type couple, and choose the operating temperature range according to the application. Usually the working temperature of KX is -20～100℃, and the wide range is -25～200℃. The error of ordinary grade is 2.5℃, and that of precision grade is 1.5℃. 2. Contact connection 1. Selection of compensation wire The compensation wire must be correctly selected according to the type of thermocouple used and the occasion used. For example, K-type couple should choose the compensation wire of K-type couple, and choose the operating temperature range according to the application. Generally, the working temperature of KX is -20～100℃, and the wide range is -25～200℃. The error of ordinary grade is ±2.5℃, and that of precision grade is ±1.5℃. 2. The contact connection is as close as possible to the 2 contacts of the thermocouple terminal, and try to keep the temperature of the 2 contacts the same. The temperature at the connection point of the instrument terminal should be as consistent as possible. Where there is a fan in the instrument cabinet, the contact point should be protected not to make the fan blow directly to the contact point. 3. The length of use is because the signal of the thermocouple is very low, in the microvolt level. If the distance used is too long, the signal attenuation will be coupled with the interference of the strong electricity in the environment, which can cause the signal of the thermocouple to be distorted, resulting in measurement and control of the temperature. Inaccurate, temperature fluctuations will occur when the control is severe. According to our experience, it is usually better to control the length of the thermocouple compensation wire within 15 meters. If it exceeds 15 meters, it is recommended to use a temperature transmitter to transmit the signal. The temperature transmitter converts the potential value corresponding to the temperature into a direct current for transmission, which has strong anti-interference. 4. Wiring Compensation wire wiring must be far away from power lines and interference sources. Where crossing is unavoidable, the crossing method should also be adopted as much as possible, not parallel. 5. Shielded compensation wire In order to improve the anti-interference of the thermocouple connection wire, a shielded compensation wire can be used. The effect is better for occasions with many on-site interference sources. However, the shielding layer must be strictly grounded, otherwise the shielding layer will not only not play a shielding role, but will enhance interference. 6. u200bu200bPay attention to the following points for the selection of compensation wire: a. The compensation wire must be used in conjunction with the corresponding thermocouple (that is, the nickel-chromium-nickel-aluminum thermocouple should be matched with the nickel-chromium-nickel-aluminum compensation wire). B. Connect the positive pole of the compensation wire to the positive pole of the thermocouple, and connect the negative pole to the negative pole. C. The temperature of the two connection points of the compensation wire and the thermocouple should be the same, and should not exceed 100 degrees. D. After the thermocouple is connected to the compensation wire, the reference terminal temperature should be corrected.
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