Pressure transducer-tensiometer (PTT) systems can be used to continuously monitor soil pore water pressure and the hydraulic gradient distribution in a field, and under laboratory conditions over relatively short time intervals. A reliable laboratory calibration of a PTT system can determine the effects of temperature fluctuations on output readings in the field. Laboratory calibrations of 20 PTTs were conducted under constant pressures of 0, − 25, − 50 and − 75 kPa and constant temperatures of 5, 15, 25 and 48 °C. Twenty Bourdon gauge tensiometers (BGTs) and pressure transducers (PTs) were also calibrated to check changes in the sensitivity and effectiveness of the PTT system, when the Bourdon gauge of the tensiometer is replaced by a PT. Readings of all the three systems revealed that pressure values gradually declined with an increase in temperature. With a temperature change from 5 to 48 °C, the pressure values at constant pressures of 0, − 25, − 50 and − 75 kPa decreased by 0, 3.7, 4.1 and 4.5 kPa for the BGT; 2.05, 2.16, 2.23 and 2.44 kPa for PT and 2.53, 2.87, 2.88 and 3.17 kPa for PTT. As the influence of temperature on the calibration curve of the PTT and PT systems was different, it is recommended that the complete PTT system should be calibrated in the laboratory to adjust the output readings to the anticipated temperature in the field. Key words: Tensiometer, tensiometer-pressure transducer, soil pore water pressure, hydraulic gradient
