Fringing Field Capacitive Smart Sensor Based on PCB Technology for Measuring Water Content in Paper Pulp
Fringing Field Capacitive Smart Sensor Based on PCB Technology for Measuring Water Content in Paper Pulp
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DOI：
10.1155/2020/3905804
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发表时间：
2020-03-04
影响因子：
1.9
通讯作者：
Dias, Jose Siqueira
中科院分区：
文献类型：
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作者：
Morais, Flavio;Carvalhaes-Dias, Pedro;Dias, Jose Siqueira
提出了一种基于印刷电路板（PCB）技术的电容式智能传感器，用于测量造纸机湿部纸浆中的含水量。所开发的传感器将信号处理电路集成在同一PCB中。它是一种手持便携式设备，其输出通过蓝牙无线连接发送到阅读设备，使传感器操作员在造纸机湿部周围的移动性更加轻松。原型在实验室中进行了测试，使用丝网模拟造纸机的末端，我们能够测量并轻松检测何时达到造纸过程中所需的90%至92%的含水量。在各种湿度水平下的电容测量的标准偏差比平均值小四个数量级。智能传感器在20摄氏度至40摄氏度的温度范围内进行了测试，纸浆的重量含水量为91%。由于电容随温度的变化实际上是线性的，我们提出了一个简单的线性补偿方程来校正所观察到的灵敏度与温度。为了保持信号处理电路小、低成本、简单和鲁棒，使用新颖的直接接口传感器到微控制器电路技术来进行电容测量，允许在没有高频振荡器的情况下测量小的电容偏差。结果表明，可以将信号处理电路集成在PCB叉指型传感器的顶层中，而不会增加噪声或降低电容传感器的性能。
We present a capacitive smart sensor based on printed circuit board (PCB) technology to measure the amount of water content in a paper pulp at the wet end of a paper machine. The developed sensor incorporates in the same PCB the signal processing circuits. It is a handheld portable device, and its output is sent to the reading equipment using a Bluetooth wireless connection, providing to the sensor's operator ease of mobility around the wet end of a paper machine. The prototype was tested in a laboratory, using a wire mesh to emulate the end of a paper machine, and we were able to measure and easily detect when it reaches the water content in the range of 90% to 92%, as required in the paper fabrication process. Standard deviation of the capacitance measurements at various moisture levels is four orders of magnitude smaller than the mean. The smart sensor was tested in the 20 degrees C to 40 degrees C temperature range, in a paper pulp with a gravimetric water content of 91%. Since the variation of capacitance with temperature is practically linear, we propose a simple linear compensation equation to correct the observed sensitivity with the temperature. To keep the signal processing circuits small, low cost, simple, and robust, a novel direct interface sensor to microcontroller circuit technique was used to make the capacitive measurement, allowing for measuring small capacitance deviations without high-frequency oscillators. It was shown that it is possible to integrate the signal processing circuits in the top layer of the PCB interdigitated sensor without adding noise or degrading the performance of the capacitive sensor.