光散射法扬尘在线监测仪自动校零模式及其影响

Study on automatic zero correction mode and its influence on light scattering online dust monitor

自动校零功能是要求光散射法扬尘在线监测仪在长期使用过程中数据漂移后进行自我修正,以减少缺乏自净功能带来的测量误差。该文搭建扬尘监测仪校准装置,探究市场上常见3类自动校零结构(无切换阀、前置切换阀、后置切换阀)高浓度淹没实验前后对零点测量效率、仪器采样流量、测量误差的影响。研究发现3种结构仅能实现“零点测量”,未实现零点校准,而零点测量效率为无切换阀>后置切换阀>前置切换阀。此外,前置切换阀积灰容易造成传感器二次污染,后置切换阀易造成传感器污染,均会影响传感器测量误差。因此,光散射扬尘在线监测仪需与传感器校零算法或定期清洗等方式相结合来最终实现目的,现有标准、规范需进一步细化对自动校零功能的检测方法和性能指标的设定,从而提高扬尘在线监测仪测量准确性和稳定性。

Automatic zero calibration function were required to light scattering online dust monitors to selfcorrected after data drift in the process of long-term use,so as to reduce the measurement error caused by lack of self-cleaning function.A dust monitor calibration device was set up to study the effects of automatic zero calibration structures including no switching valve,front switching valve and rear switching valve and the highconcentration inundate experiment on zero-point measurement efficiency,instrument sampling flow rate and measurement error of the online dust monitors.It is found that the three structures can only realize zero point measurement,but failed in zero point calibration.The zero point measurement efficiency is:no switching valve>rear switch valve>front switch valve.In addition,the dust accumulation of the front switching valve is easy to cause secondary pollution of the sensor,and the dust accumulation of the rear switching valve is easy to cause second pollution of the sensor,which both affected the sensor measurement error.Therefore,the online light scattering dust monitor should be combined with sensor zero calibration algorithm or periodic cleaning to achieve the final goal.The existing standards and specifications need to further refine the detection method of automatic zero calibration function and the setting of performance indicators,so as to improve the accuracy and stability of online dust monitor measurement.