Different Optical Fiber Sensor Designs for Liquid Flow Monitoring

Design and operation of three different optical sensors based on the intensity modulation are reported in this article. These sensors are measuring absence or presence of any liquid and the measurement variable is refractive index and optical absorption. Reported devices can also check the presence of air bubbles in the liquid flow line. Performance of these sensors is tested as a liquid flow monitoring device while using different light sources. Sensor #1 uses a simple cell with the long transmitter and receiver optical fibers. Sensor #2 utilizes a small cell assembly that includes the short transmitter and receiver fibers. Sensor #3 employs a quartz flow cell with the direct light illumination and detection. A voltage difference of about 1.65 V for the case that water flows in the flow cell is measured for sensor #1. For this sensor the wet dry difference is about 32.92 % of the full scale and the bubble effect is about 6.17 % of the full scale, which is a high sensitivity. For sensor #2 using white lamp, there is a voltage difference of about 1.6 V for the case that water flow. There is a voltage difference of1.1 Vfor the case of water flow in sensor #3. The reported results are promising and verify the successful operation of all the sensor systems depending on the application condition and requirements