A system for detecting a characteristic of a fluid. In one example, the system includes a tube, a float, a sensor, and a controller. The tube is configured to receive the fluid. The float is located within the tube. The sensor is configured to sense a position of the float. The controller is configured to receive, from the sensor, the position of the float, and determine a characteristic of the fluid based on the position of the float. The characteristic may be a density or a concentration.