TDS (Total Dissolved Solids) is a measure of the combined total of organic and inorganic substances contained in water. It can be a general indicator of water quality. The unit of TDS measurement is ppm or milligrams per liter (mg/L). The larger the TDS value, the more dissolved substances in water.
In many consumer products, the TDS value is calculated by measuring the conductivity of water (in uS/cm), which is roughly 1 ppm TDS = 2uS/cm. Using parallel cylindrical electrodes with fixed distance as the measuring probe, the probe is placed in water and a voltage is applied between the two electrodes to measure the conductivity.
Factors affecting the accuracy of TDS measurement include water temperature, flow rate, etc. In general, the standard measurement temperature is 25°C. For each 1°C increment, the TDS value increases by about 2%. When measuring TDS, the water temperature is usually measured together for temperature compensation.
The Holtek TDS Workshop platform integrates the rich functions of TDS measurement, temperature measurement, button input, display, communication etc. You can complete the configurations and generate MCU codes in several steps. The TDS platform also has a calibration monitoring window to calibrate the device and monitor the measured TDS value continuously. The measurement records can be exported to an excel file.
Holtek provides four evaluation boards to work with the TDS platform:
TDS Module ESK-TDS-66F0176 supports single-channel measurement of TDS and temperature. But it does not support the LCD, LED and button functions of the TDS Display Board (ESK-TDS-100). Either the UART or IIC can be used for communication.