The PSP Data logger is a micro-controller based Data Acquisition System, and designed to measure PSP voltage. The unit has high input impedance and accuracy. This Instrument measures input signal and displays measured data on a Graphic LCD with multi-character alphanumeric data display, directly in engineering units. The GPS coordinates of the measurement site is also displayed and stored with PSP value. The data-logger stores collected pipeline survey data on a non-volatile memory which is always safe, regardless of battery status. The unit is ideally suited for soil potential (PSP) data logging for field PSP surveys and provided with Windows Based software for TLP data downloading and PSP data retrieval. The unit is hand held type conforming to IP67 and has built-in rechargeable batteries. The batteries may be charged with battery charger supplied along with the data logger. Use of latest low power integrated circuits and high speed ADC make the unit ideal for reliable, long term usage and accurate measurements. The operating parameters like calibration factor, real time, interrupter on/off time, are all key board programmable. The PSP data logger has ± 0 to 10,000 mV range and input impedance >50MOhm. The data logger may be synchronized with TRU Current Interrupter for accurate measurement. PSP measurement during ON and OFF period is done , after start of respective period with a delay period of 200 m-sec. Highest reading obtained during ON period is memorized as ‘LINE ON PSP’ and lowest reading obtained during ‘OFF’ period is memorized as ‘LINE OFF PSP’. At cased crossing locations, casing ON and OFF PSP measurements are memorized as “casing PSP’. Combined psp & casing potential report is generated. Non-volatile memory is provided to store data and GPS parameters. Measurement data is stored in non-volatile memory, in cyclic manner and remains intact even after removal of batteries. Windows compatible software is provided to down load TLP data to unit and retrieve measurement and TLP data, data to PC through serial port for analysis. The unit has rugged hand held construction and suitable for field use.