The conductivity sensor is a two-pole cell whose resistance varies as a result of the conductivity of the liquid it is immersed in. That conductivity will be proportional to the conductance of the sensor (the inverse of its resistance), multiplied by the constant cell, in the case of this sensor around 1cm-1, leading to a value in Siemens per centimeter (S/cm). For an accurate measurement, calibration should be performed. A two-point calibration is recommended, using control solutions with conductivity as close as possible to the target environment.
To power the conductivity sensor, an alternating current circuit has been installed in order to avoid the polarization of the platinum electrodes. This current's frequency can be set at four different values (100Hz, 1kHz, 10kHz and 100kHz) to adapt the measurement to the optimal operation point, which will be a function of the conductivity of the liquid and the characteristics of the sensor. For the sensor integrated in the Smart Water Board, it is recommended to use a 100Hz frequency of conductivities lower than 50ÁS/cm, 1kHz between 50ÁS/cm and 5mS/cm, 10kHz between 5mS/cm and 500mS/cm, and 100kHz for conductivities higher than 500mS/cm.
Be sure to keep the sensor at least 5cm from the surroundings to ensure it is not affected by conductivity of objects around it.
Water Conductivity Sensor Features
- Type: Two-electrode sensor
- Electrode Material: Platinum
- Conductivity Cell Constant: 1 ▒ 0.2 cm-1
Compatible with Waspmote This sensor can be used in a Waspmote wireless sensor platform by plugging it into the Waspmote Smart Water Sensor Board.