A new and compact system based on a personal computer has been developed for on-line reactor physics measurements on research reactors (PARR-1 and PARR-2). The system can perform determination of control rod worth along with its associated error, reactor shutdown margin and excess reactivity. This is done by analyzing the time dependent pulse signal from a neutron detection channel. The system utilizes a locally designed pulse acquisition card interfaced with the PC which works in the multi input multi channel scaling (MCCS) mode. The total time for the measurement of reactivity worth of a single or bank of control rods is less than three minutes. Because of its fast speed and ease of operation the system can be effectively utilized for the analysis of various subcritical configurations of the upgraded LEU PARR-1 core, both prior to and during the reactor commissioning. This report describes the results of control rod worth measurements and determination of shutdown margin and excess reactivity under different operating conditions on the PARR-1 and PARR-2 cores. The application of the systems for reactivity determination in case of high subcritical core and large gamma back-ground is also discussed. (author). 4 fig.