The parallel interface was developed for the purpose of digital data on-line transfer from ionization chamber connected vibrating reed electrometer to the personal computer (PC) . This system is applicable for the electrometer that has the digital data output and the control function of BCD code, and the measurement procedure can be controlled by the software of PC. Practical applications of this simple measurement system have been demonstrated for three experiments. One is the routine tritium concentration monitoring in air at the tritium laboratory. Second is a special tritium monitoring in a case of the tritium target exchange work for the D-T neutron generator. The third application is shown on the tritium release-rate measurement from the tritium adsorbed SS materials, where tritium water vapor was continuously monitored for 100 minutes, and the least square analysis of the obtained data was also made in the same PC.