The General Tools RDXL4SD portable 4-Channel Datalogging Thermometer is a handheld thermometer/datalogger with backlight display and built-in analysis functions. The RDXL4SD datalogger is powered by an internal battery and is capable of sampling, processing and displaying measurements without being connected to a computer. With their high resolution and fast analog to digital converter (ADC), the RDXL4SD meet the majority of data logging requirements in most industrial applications. Real-time SD memory card data logger, built-in clock and calendar, real time data recorder, and sampling time set from 1 to 3600 seconds comes standard. Data logger can log data manually by setting the sampling time to zero.