Design and Development of Opto-Resistive Type Quasi-Digital Sensor and Instrument for Online Assessment of the Quality of Lubricant Oil

In rotating machinery, the color of lubricant oil changes due to oxidation, degradation, and contamination. It is a crucial parameter to cognize the healthiness of the lubricant oil. This paper presents the design and development of a low-cost, high-precision quasi-digital sensor with an opto-resistive technique to detect the color of the lubricant oil with a microcontroller (PIC18F4550)-based instrument. The developed instrument reads the sensor output, displays the condition of the lubricant oil on LCD, announces the alarm to alert the operator, and communicates the healthiness of the lubricant oil to the computer. As per the ASTM D1500 standard, the color scale of the lubricant oil varies from 0.5 to 8.0. In the studies conducted at the laboratory, this color scale corresponds to the sensor output frequency in the range of 76.87–61.63 kHz. The sensitivity of the color sensor is 1905 Hz/color code. Apart from this, an additional sensor is provided to measure the turbidity of the lubricant oil, which helps in compensating the error in color scale due to turbidity. In addition to revealing of lube oil color, it can also detect the size of the particles in the lubricant oil. To perform these tasks, an algorithm and an application software have been developed and loaded into the flash memory of the microcontroller.