The melt temperature variation during plasticizing of the injection molding has been reported for a long time, but it has not been considered as an important factor in the field because it is very difficult to measure it during processing. In the previous research, we examined the melt temperature variation according to the screw rotation speed, metering stroke, the dwelling time and barrel heater profile by a newly developed sensor with a higher sensitivity than the conventional sensors flush-mounted at the adaptor wall. The sensor was in the middle of the melt stream of the nozzle adaptor and measured the melt temperature passing by the sensor during slow purging. In this work, we developed a temperature sensor system to measure the melt temperature at the screw tip. A thermocouple is installed at the screw tip so that the melt temperature passing through the check ring could be measured. In this type of sensing system, the data acquisition has a difficulty to be sent out of the rotating screw. Conventionally, the signal is transmitted through a slip ring or an analog telemetric device to external data logger. We developed a digital data acquisition system using a Raspberry Pi computer with a WiFi communication. The temperature signal line is connected through the screw center hole to an amplifier and an ADC (analog-to-digital converter) installed at the back of the screw. The converted digital data is acquired and stored by the computer. The signal conditioning system and the computer are battery powered. The data stored in the computer is uploaded to an external server after one molding cycle via WiFi communication. The sensitivity of the screw-tip sensor and the performance of the system were evaluated. The same experiments as in the previous research were carried out to compare the temperature measured by the new system with the previous one measured by the sensor installed at the nozzle adaptor.