Abstract: This paper introduces a nonlinear correction method for vacuum measurement based on cubic spline interpolation. The establishment of the cubic spline interpolation function and its implementation on a computer system are discussed. The interpolation results are analyzed, and finally, the results are stored in tabular form in the Flash memory of a Freescale microcontroller. The corresponding correction function is obtained in the microcontroller program using a table lookup method. The results show that this method has the characteristics of high accuracy and high speed, and has good application value, proving its feasibility. Keywords: vacuum measurement; nonlinear compensation; spline interpolation; sensor [b][align=center]Nonlinear Compensation of Thermocouple Circular Canal Sensor in the Vacuum Measurement Dong Chuangang, Sun Tongjing[/align][/b] Abstract: A method of nonlinear compensation of vacuum measurement based on cubic spline interpolation is presented in this paper. The establishment of cubic spline interpolation function and its implementation on the computer system are discussed, and the interpolation result is analyzed. Finally, the result is saved in the way of table into the Flash of Freescale MCU. The relevant compensation function is obtained by the method of table in the program. The results show that the method has the characteristics of high precision and fast rate, and has good value to be extended and is feasible. Key words: vacuum measurement; nonlinear compensation; spline interpolation; sensor 0 Introduction Thermocouple gauges are sensors used to measure the negative pressure of gas. They utilize the thermal conduction phenomenon of gas to measure gas pressure. When a thermocouple gauge operates in constant current mode, a constant current is passed through the thermocouple wire. The thermocouple measures the temperature of the wire. At higher pressures, the gas has better thermal conductivity, resulting in more heat dissipation from the wire and a lower wire temperature. Conversely, at lower pressures, the gas's thermal conductivity decreases, leading to a higher wire temperature. Converting the millivolt output of the thermocouple into a pressure value achieves vacuum measurement. During measurement, the pressure value is a function of the thermocouple's output millivolt value, p = f(v), where v is the thermocouple output value and p is the pressure value. Because there is a significant nonlinearity between the thermocouple sensor's output signal voltage v and the measured parameter, gas pressure p, and this nonlinearity cannot be described by a simple mathematical formula, it is necessary to correct and linearize the nonlinearity to improve measurement accuracy. There are two main types of linearization methods: hardware linearization and software linearization. In systems involving microcomputers, software methods are often used to save on hardware investment and simplify the system structure. This paper uses cubic spline interpolation. For details, please click: Nonlinearity Correction of Thermocouple Gauge Sensors in Vacuum Measurement.