Voltcraft dl 191 voltage and current usb data loggers voltcraft dl 191v the voltcraft dl 191v voltage data logger is a compact data logger in a usb drive enclosure for monitoring and recording voltages the logging interval is adjustable from 0 0025s 400hz to 24hrs by software on the computer the internal lithium battery makes for a long operating period it is able to store 32 000 measure values the recorded data can be read and processed with the enclosed measuring software which has a