TRMS single-phase current Datalogger XL421 is a Data Logger capable of measuring and recording the true root mean square(TRMS) value of AC current up to 2500A in single-phase electric systems for different applications (evaluation of load currents, rated powers of transformers, etc.). The device has a comfortable mobile structure with integrated flex clamp jaws which allow surrounding also a big-sized cable or bar. Thanks to a an advanced memory management algorithm it is possible to monitor a system even for a long time. The device starts recording with a sampling period which can be selected through software among 1, 6, 30 and 60 seconds and, when memory is almost full, the previously recorded values are “re-sampled” according to the subsequent value of the sampling period, thus freeing part of the memory; the device then goes on recording new values, using the new measuring interval. In this way, it is possible to keep the device recording up to approximately 1 year. Each recording is kept stored in the internal memory and can be downloaded and managed by PC always through a dedicated software. Data Logger XL421 is also provided with a special adhesive strap which makes it possible to place it in any place in the installation where measuring is needed. The high protection rating (IP65) makes this device fully reliable also under extreme operating conditions.