KX-GS-VPV compensation wire

KX-GS-VPV compensation wire

KX-GS-VPV compensation wireWholesale model production

The dual platinum rhodium thermocouple does not require compensation wires, as mentioned earlier. It is said that compensation wires are needed to compensate for the temperature at the reference end of the thermocouple. However, among commonly used thermocouples, the dual platinum rhodium (Platinum Rhodium 30-Platinum Rhodium 6) thermocouple with division number B is an exception as it does not have compensation wires. In other words, in practical applications, it is generally not necessary to use compensation wires. Double platinum rhodium thermocouples are commonly used for temperature measurement in the range of 1300~1600 ℃ (platinum rhodium platinum thermocouples are usually used for temperatures ≤ 1300 ℃). The thermoelectric potential in the low-temperature range is surprisingly low, such as only 0.033mV at 100 ℃ and 0.178mV at 200 ℃. Compared with the average thermoelectric potential of 0.700mV per 100 ℃ in the entire temperature measurement range (0~1800 ℃), the difference is significant, so even without compensation, the error caused is very small. For example, when the hot end temperature is 1300 ℃ and 1600 ℃, such as when the reference end temperature t1=100 ℃, the error caused is ± 3.0 ℃, and when t1=120 ℃, the error caused is ± 5.0 ℃, both of which meet the requirement of ± 5 ℃ for using ordinary compensating wires. However, it is worth noting that when t1=200 ℃, it may cause an error of ± 16.3 ℃. Therefore, for dual platinum rhodium thermocouples, although compensation wires are usually not used, the limiting condition is that the reference terminal temperature t1 ≤ 120 ℃, otherwise it will cause significant errors. In uncommon thermocouples, nickel cobalt nickel aluminum thermocouples have almost zero thermoelectric potential below 200 ℃ and do not require compensation wires, while nickel iron nickel copper thermocouples have negligible thermoelectric potential below 50 ℃ and do not require compensation wires within this temperature range.

For early moving coil instruments equipped with thermocouples, there are two requirements for the line resistance of compensating wires: 5 Ω and 15 Ω. When the thermocouple installation site is far away from the moving coil meter, or when using compensating wires containing copper nickel materials with division marks K, N, E, J, T, etc., the line resistance is relatively high. When selecting, attention should be paid to choosing compensating wires with larger cross-sections. For example, when using a dynamic coil instrument with an external 15 Ω line resistance E scale, if the compensating wire section used is 1.0 mm2 and 2.5 mm2, and the corresponding unit length line resistance is 1.25 Ω/m and 0.5 Ω/m, respectively, the maximum allowable length of the compensating wire is only 12 m and 30 m. If not careful during design, this length can easily exceed it, causing measurement errors.