Automatic TDS meter and water level control

Abstract

The purpose of this project is to develop a system that protects more the patient during the dialysis procedure. The system should prohibit any reversed flow of the water (i.e. detecting the Total Dissolved Solid (TDS)) and the waters level in the tank. The status of the two latter indicators may have drastic outcomes and may lead to the death of the patient. In this context, a circuit is developed in order to measure the TDS in the water continuously and to provide a feedback to take the appropriate actions. Two rods are connected to an amplifier that is a driven by an input sinusoidal wave. These rods are immerged in the water to measure its conductivity. Then, the signal is amplified and is converted to a DC voltage. The filtered output DC voltage is calibrated in terms of the conductivity of the water. Another circuit is designed and implemented to measure the waters level in the tanks that feed the dialysis machines. These tanks are placed on the roof of the hospitals where it is difficult for the biomedical engineer to check the waters level at every instant. To solve such problem, a pressure sensor was placed inside the tank to measure the waters level and to provide a continuous feedback about its status. When the tank is about 30% of its full capacity, the circuit sends a signal to turn on the reversed osmosis to pump the sterilized and deionized water into the tank and a red LED is turned on. When the tank is completely filled (100%), the circuit will trigger a signal to turn off the reversed osmosis and a green LED is turned on to indicate that the filling process of the tank is over. Thus, the developed circuits control the waters level in the tank and check the TDS in the water in order to safely stop the dialysis machine under certain conditions. The two circuits are tested and they have functioned as expected.