We have developed a combined ionic conductivity and temperature sensor package for multiphase chemical reactors, key elements of SmartChip, a flow following, data logging sensor. The initial application of the sensor is to monitor the process inside the hot and caustic chemical environment of a kraft pulp digester (pH similar to 13, temperatures from 25 to 175 degrees C, reaching a maximum of 180 degrees C and pressures up to 2 MPa). The sensor package consists of a 1000 Omega platinum resistance temperature detector (RTD) enclosed in a stainless steel container and a four-electrode conductivity sensor consisting of stainless steel electrodes and installed on a polyetheretherketone (PEEK) package. The sensor package is designed ultimately to move within the kraft pulp digester and record sensor data. The sensors were tested at temperatures of up to 140 degrees C in NaOH concentrations of 10-100 g/L as Na2O with and without the presence of wood chips. Changes in concentration were clearly discernible as changes in conductivity. The presence of chips reduced conductivity as expected, and this reduction depended on the degree of cooking. Although further calibration work is needed to quantitatively determine concentration inside a digester, process variations should be readily detectable. The average power consumption of the sensors is 5 mW, which is sufficiently low to enable autonomous operation of the sensor under battery power. The sensor packages were tested for a full kraft pulping cycle and survived with no signs of corrosion. The demonstration of conductivity measurements represents an important step toward the successful implementation of flow following measurements in the kraft pulping processes to aid process optimization and design.