The REED R6250SD is a data-logging version of REED's WBGT heat-stress meter, recording air, black-globe, and wet-bulb temperature plus humidity directly to an SD card (up to 16GB) at user-selectable sampling intervals. A dual backlit LCD, real-time clock, and hold/min-max functions make it suited to logging heat-stress exposure over a full shift for OSHA-style compliance records. This listing includes an add-on NIST-traceable calibration certificate for documented accuracy.