Key Technologies Of Liquid Refractive Index Measurement Under Environmental Disturbance

Refractive index is a basic physical property of liquid,which can reflect the concentration,density and other properties of liquid.It is widely used in industrial production.However,with precise optical components,refractive index equipment in operation would suffer unavoidable environmental disturbances,such as temperature fluctuation,and mechanical vibration,etc.These environmental disturbances would make the measurement inaccurate and bring extra system error to the measurement system.Therefore,it is necessary to improve the refractive index measuring device in view of environmental disturbances existing in the field of application.In this way,the environmental disturbances on the refractive index measuring device can be reduced as much as possible.The device's accuracy can remain high under environmental disturbance,so the application range of the refractive index measurement device would also be expended.Firstly,we analyze the principle of critical angle method of measuring liquid refractive index,discusses the influence of several common interferences to the measurement device,such as the measurement of vibration and temperature change.In view of such influence,the corresponding correction method is proposed: add a piece of standard glass to the measurement interface,use the measurement results of standard glass to correct the calibration curve obtained before,and use the corrected calibration curve to calculate the refractive index of the sample.Then,analyze the characteristics of light source required by the device based on the theory of critical-angle method,and select the proper light source for the device.In order to reduce the impact of environmental interference on the measuring device,add standard glass to the measuring interface.Select the material and size of prism and reference glass,design the optical path and conduct simulation.Standard glass and prism were bonded with optical adhesive and assembled together with sample slots.Sealants were used to seal gaps to prevent sample leakage.Aiming at the spot obtained by the detector,design the algorithm to extract the location of the light-dark boundary and reduce the noise interference.Then the calibration experiment was carried out,and the relationship between the position of the light-dark boundary and the sample refractive index was obtained.The vibration test was designed to test the stability of the measurement results in the presence of vibration.The temperature experiment was designed to test the stability of the measurement results of the device under the condition of temperature change.We also tried to measure the turbid sample.Try to measure the turbid sample and explore the influence of the turbid sample on the measurement.Finally,a field test was carried out to measure the content of raw materials in a liquid product.Specific improvements have been made to the measurement devices according to the field environment.The corresponding control program is written to enable the measuring device to measure automatically,process the acquired images in real time and display the measurement results.At the production site of this liquid product,the improved device is used to measure the material sample to verify the availability of the device.