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在用刀具——工件热电偶测量切削温度时,常采用铜——康铜补偿电路补偿刀片尾部的附加热电势。因此,研究补偿电路的误差问题是很必要的。Trigger 等人曾根据部分试验指出:在采用铜——康铜组成的补偿电路时,最大不平衡电压输出约为±0.02mv,对于切削钢料来说,测温误差为±2°F。本文通过理论分析和试验研究,证明上述结论是有局限性的。对这种补偿电路,若使用不当,在切削高温合金时不平衡电压有时可达0.34mv,温度误差有时可达(24～30)℃。本文分析了刀片尾部实际温度,补偿电阻及导线内阻对不平衡电压的影响,得出不平衡电压的计算公式,并提出了另一对误差较小的导线,可供选用。
Copper-constantan compensation circuit is often used to compensate for the additional thermoelectric potential at the tip of the blade when measuring the cutting temperature with a tool-workpiece thermocouple. Therefore, it is necessary to study the error of compensation circuit. According to some experiments, Trigger et al. Point out that the maximum unbalanced voltage output is about ± 0.02mv when using a compensation circuit composed of copper-constantan, and the temperature measurement error is ± 2 ° F for cutting steel. Through theoretical analysis and experimental research, this paper proves that the above conclusion is limited. If this kind of compensation circuit is used improperly, the unbalanced voltage may sometimes reach 0.34mv when cutting the superalloy, and the temperature error may sometimes reach (24-30) ℃. In this paper, the influence of the blade tip actual temperature, the compensation resistance and the wire internal resistance on the unbalanced voltage is analyzed. The formula of the unbalanced voltage is obtained and another pair of wires with smaller error is proposed for selection.