Refractometers are used as an efficient tool for measuring the concentration of various substances in a solution. They can be used in laboratories to measure the concentration of sampled materials or inline for real-time monitoring of the concentration of industrial liquids. PTR100_cpt is an inline compact refractometer which directly connects to the main piping. Moreover, it can be used in both clear and opaque liquids. The head and sensor processing units of the device are in the same unit. PTR100 is fully calibrated and also temperature-compensated. Measured signals are available in different units such as Brix or nD. Apart from local display of the measured signals on the LCD of the device, they can be sent to the central controllers such as PLCs or DCSs using analog 4-20 mA current signal or through Modbus RTU RS485 communication protocol.