TT Electronics/Optek Technology's OPB350/OCB350 series is configured to optimize the design effort needed to use a fluid sensor with the addition of self-calibration circuitry. The OPB350/OCB350 series is easy to use requiring only an optical device and power supply. Four lights are provided on the board that acknowledge when the device is calibrated (Green LED), that the device could not be calibrated (Red LED) and when the analog output has reached the logical trip higher than the calibration point (Blue LED) or lower than the calibration point (Green LED). The internal phototransistor load resistance can be set for three different values (~2.5 k, ~9.6 k, or ~27 Ω). A Reset/Clear pin is provided for remote signaling to calibrate the system.